Add authored Age skies and celestial pages (#44)

README.md

@@ -105,6 +105,36 @@ JEI is optional; vanilla crafting
 recipes and all writing interactions work without it. For a development client
 with JEI, run `./gradlew runClient -PwithJei=true`.
 
+Four Crystal Shards craft one Crystal Block; eight Crystal Blocks around an
+empty crafting-grid center make one Book Receptacle. Picking up a shard unlocks
+the block recipe, and picking up a block unlocks the Receptacle recipe. The
+existing Ink Vial recipe uses two black dyes, a glass bottle, and a water
+bucket; the empty bucket stays in the crafting grid. These JSON recipes appear
+in JEI when it is installed and can be replaced by a data pack at
+`data/rivencraft/recipe/<recipe_name>.json`. To test a replacement, use a fresh
+world or `/reload`, then check the result in a crafting table and vanilla
+Crafter. A vanilla Lectern converts to a Rivencraft Book Stand when a Rivencraft
+book or page is placed on it; this in-world interaction has no JEI guide.
+With Create installed, Crystal Blocks and Book Receptacles have an optional Ponder scene
+showing crystal-frame construction, book activation, and a parrot crossing the portal. Use the Ponder shortcut
+while hovering either item; Rivencraft does not require Create to run.
+Crystal frames may stand vertically or lie flat: a 3×3 Crystal Block ring with
+an empty center forms a horizontal portal when a Book Receptacle is attached to
+the top or underside of one of its blocks. Insert a bound Linking or Descriptive
+Book to activate it; the book remains visible on the receptacle. A Linking Book aimed at its
+own dimension still opens a visual portal, but travel requires Intra Linking.
+
+Sky writing includes eight color pages and a Static Sky page. Multiple sky-color
+pages blend their colors, tinting the Age sky, book preview, and the fallback
+surface of portals linked there. Multiple celestial-color pages blend for the
+next written sun or moon. An Age may have no suns or moons at all;
+Static Sky animates the sky with television-like noise. Sun and Moon pages add
+independent bodies; preceding color, size, angle, period, phase, and direction
+pages configure the next body. The third and each subsequent sun add increasing
+instability. Newly generated page-free Ages also choose a deterministic sky,
+color, and celestial arrangement from their Age seed; older saved Ages retain
+their previous sky.
+
 Craft a Book Binder from three iron ingots and five planks. Put leather or an
 empty Notebook in the left cover slot. Enter a title, then place a Link Panel
 Page first in the horizontal page strip. Click a page in the strip with a
@@ -184,7 +214,7 @@ Linking creates a bound Return Link to the exact source position and orientation
 according to the configured Return Link policy.
 
 Server owners can set `descriptive_books.return_link_mode` in Rivencraft's
-server config to `ON_CREATION` (default), `ALWAYS`, or `DISABLED`.
+server config to `DISABLED` (default), `ON_CREATION`, or `ALWAYS`.
 Age creation, persistence, lifecycle commands, configuration, backups, and
 administrator recovery are documented in [docs/AGES.md](docs/AGES.md).
 Data-pack runtime profiles are documented in
@@ -194,7 +224,7 @@ Data-pack runtime profiles are documented in
 
 - A Java 21 JDK
 - Minecraft 1.21.1
-- NeoForge 21.1.251 or newer in the 21.1 line
+- NeoForge 21.1.264 or newer in the 21.1 line
 - Dynamic Dimensions AR Edition 0.9.1 and Bad Packets 0.8.2 (client and server)
 
 Create is optional. When installed, Rivencraft uses its Ponder renderer for

build.gradle

@@ -132,6 +132,8 @@ neoForge {
 
         server {
             server()
+            // Keep dedicated compatibility runs away from the normal dev world.
+            gameDirectory = project.file(project.findProperty('serverRunDir') ?: 'run')
             programArgument '--nogui'
             systemProperty 'neoforge.enabledGameTestNamespaces', project.mod_id
         }

docs/AGES.md

@@ -69,10 +69,9 @@ definition.
 Rivencraft writes gameplay settings to the world/server configuration managed
 by NeoForge. `descriptive_books.return_link_mode` accepts:
 
-- `ON_CREATION` (default): create one Return Link the first time a player
-  enters each Age.
+- `DISABLED` (default): never create Return Links automatically.
+- `ON_CREATION`: create one Return Link the first time a player enters each Age.
 - `ALWAYS`: create a Return Link after every successful Descriptive Book trip.
-- `DISABLED`: never create Return Links automatically.
 
 Each client has a separate `rivencraft-client.toml`. Its `book_preview.mode`
 setting accepts `AUTO`, `IMMERSIVE_PORTALS`, `PONDER`, or `LEGACY`. This changes

docs/AGE_CLOUD_PLATFORM.md

@@ -1,7 +1,7 @@
-# Age arrival cloud platform
+# Age arrival platform
 
-Newly created Ages now place a 5×5 solid cloud platform instead of cobblestone at their saved spawn. The block has full collision, passes skylight, renders translucently, has no loot table, and cannot be obtained with pick-block. Existing Ages retain their already-placed platform; this change does not overwrite a player's saved world.
+Newly created Ages place a 5×5 solid platform instead of cobblestone at their saved spawn. The block has full collision, renders as an opaque full block, breaks as easily as glass (0.3 hardness), has no loot table, and cannot be obtained with pick-block. Existing Ages retain their already-placed platform blocks, which adopt the new appearance and hardness without altering saved terrain.
 
-The block texture is `assets/rivencraft/textures/block/cloud_platform.png`, verified at exactly 16×16 RGBA. Legacy's supplied assets contain no cloud-block texture, so this one was generated with the built-in image tool, then reduced by nearest-neighbor sampling. The final prompt requested a seamless Minecraft block-face pixel-art tile with 2–3 chunky white, icy-blue, and powder-blue cloud swirls, genuine transparent holes between them, strong 16×16-scale contrast, and no background or text.
+The model reuses `assets/rivencraft/textures/block/crystal_block.png`, the 16×16 Legacy crystal tile. The former generated cloud texture is removed. The internal block ID remains `rivencraft:cloud_platform` to preserve saved worlds.
 
 The separate [decay provider](INSTABILITY_DECAY.md) protects the saved spawn area by position, so its protection remains in force regardless of the platform's material.

docs/AGE_PROFILES.md

@@ -40,6 +40,27 @@ profiles, not claims that Legacy had identically named terrain symbols.
 Every family retains a safe cobblestone arrival platform. An omitted terrain
 page still uses the deterministic seed-selected profile.
 
+### Cave terrain and Legacy
+
+Legacy's closest terrain generator is its Nether terrain symbol: it owns an
+Age-seeded octave-noise generator, accepts terrain/sea materials, and sets a
+sea level of 32. Legacy's separate Caves symbol instead registers a terrain
+alteration that carves additional caves; it is not a terrain generator.
+Minecraft 1.21.1 no longer has Legacy's 1.12.2 height and generation pipeline,
+so Rivencraft Cave terrain uses `minecraft:caves` noise and the modern Cave,
+Nether, and tagged modded Nether biome decorations. It cannot reproduce the
+exact Legacy noise or its older vertical layout. The Caves feature page
+remains a separate additive carver for other suitable terrain.
+
+Cave Ages search for safe spawn footing from Y=64 downward rather than using
+the cave roof; if necessary, the usual cloud platform is placed at Y=63.
+Weather is clear and Serene Seasons is disabled in Cave terrain. Authored
+Weather, Season, and Celestial pages (including time modifiers) are retained
+in the book but have no effect on the Cave Age; each adds 100 base instability.
+The same policy applies to randomly selected Cave terrain and persists through
+save/reload. Cave biome selections remain limited to Cave and Nether biomes;
+surface-biome completion is not used for Cave terrain.
+
 The separate **Floating Islands** feature page adds rare high-altitude island
 clusters above Standard, Amplified, Sky Islands, Flat, or Void terrain; it does
 not replace the terrain page. The feature is seeded by the Age and saved with the written

docs/ASSET_PROVENANCE.md

@@ -19,12 +19,12 @@ project's GNU LGPL v3 license. Rivencraft itself uses the same license.
 | `assets/rivencraft/textures/block/book_binder_press.png` | `assets/mystcraft/textures/entity/bookbinder/press_part.png` | `9bc8ddc061845df0cd5ea47f4fdef773cff786ae` | Namespace/path rename only; Book Binder model uses this press texture |
 | `assets/rivencraft/textures/gui/book_binder_legacy.png` | `assets/mystcraft/gui/pagebinder.png` | `9bc8ddc061845df0cd5ea47f4fdef773cff786ae` | Namespace/path rename only; Book Binder GUI uses the original 176×181 panel |
 | `assets/rivencraft/textures/gui/ink_mixer_legacy.png` | `assets/mystcraft/gui/inkmixer.png` | `9bc8ddc061845df0cd5ea47f4fdef773cff786ae` | Namespace/path rename only; Ink Mixer GUI uses the original 176×181 panel |
-| `assets/rivencraft/textures/block/ink_mixer_top.png`, `ink_mixer_side.png`, `ink_mixer_bottom.png` | `assets/mystcraft/textures/blocks/inkmixer_top.png`, `inkmixer_side.png`, `inkmixer_bottom.png` | `9bc8ddc061845df0cd5ea47f4fdef773cff786ae` | Namespace/path rename only; Rivencraft supplies its own block model |
+| `assets/rivencraft/textures/block/inkwell_base.png`, `inkwell_cup.png`, `ink.png`, `ink_glass.png` | `assets/mystcraft/textures/entity/inkwell/` counterparts | Legacy 0.13.7.06 local extraction | Byte-identical copies used by the ported Ink Mixer geometry; the paper overlay uses vanilla white concrete instead of Legacy's black surface |
 | `assets/rivencraft/textures/item/linking_book_unwritten.png` | `assets/mystcraft/textures/items/unlinked.png` | `9bc8ddc061845df0cd5ea47f4fdef773cff786ae` | Namespace/path rename only |
 | `assets/rivencraft/textures/item/page_link_panel.png` | `page_background.png` and `PageBuilder.BasicPageSprite` | `9bc8ddc061845df0cd5ea47f4fdef773cff786ae` | Reproduces the legacy 160 px scale, black panel at `(25,30)`–`(135,75)`, and 128 px resample |
 | `assets/rivencraft/textures/gui/symbolcomponents.png` | `assets/mystcraft/textures/symbolcomponents.png` | `9bc8ddc061845df0cd5ea47f4fdef773cff786ae` | Byte-identical shared 512×512 component sheet for client-side page composition |
 | Runtime-composed symbol pages (`SymbolPageTextures`) | `page_background.png`, `textures/symbolcomponents.png`, `WordData`, `ModSymbols`, and `PageBuilder.PageSprite` | `9bc8ddc061845df0cd5ea47f4fdef773cff786ae` | Replaces the six pre-generated symbol PNGs; layers four poem words on the shared page background and caches bounded client textures |
-| `assets/rivencraft/textures/block/crystal_block.png` | `assets/mystcraft/textures/blocks/crystal.png` | Legacy 0.13.7.06 local extraction | Exact 16×16 blue tile shared by Crystal Block and Budding Crystal models after removing a byte-identical duplicate |
+| `assets/rivencraft/textures/block/crystal_block.png` | `assets/mystcraft/textures/blocks/crystal.png` | Legacy 0.13.7.06 local extraction | Exact 16×16 blue tile shared by Crystal Block, Budding Crystal, and the non-dropping Age arrival platform; its former cloud sprite is removed |
 | `assets/rivencraft/textures/block/{small,medium,large}_crystal_bud.png`, `crystal_cluster.png` | Minecraft 1.21.1 `textures/block/{small,medium,large}_amethyst_bud.png`, `amethyst_cluster.png` | Minecraft 1.21.1 | Original 16×16 alpha masks and silhouettes preserved; hue shifted toward Legacy blue, with brighter saturation; exported as 8-bit RGBA (not indexed PNG) |
 | `assets/rivencraft/textures/item/crystal_shard.png` | Original sprite generated with OpenAI ImageGen from the Legacy crystal palette | 2026-10-05 | Cropped and nearest-neighbor scaled to 16×16 |
 | `assets/rivencraft/sounds/linking/link-fissure.ogg` | `assets/mystcraft/sounds/linking/link-fissure.ogg` | Legacy 0.13.7.06 local extraction | Namespace/path rename only; plays when a Star Fissure returns an entity home |
@@ -32,6 +32,8 @@ project's GNU LGPL v3 license. Rivencraft itself uses the same license.
 | `assets/rivencraft/textures/block/book_receptacle.png` | `assets/mystcraft/textures/blocks/book_receptacle.png` | Legacy 0.13.7.06 local extraction | Byte-identical 16×16 face tile; modern block model recreates the Legacy thin slab |
 | `assets/rivencraft/textures/block/crystal_portal.png` and `.mcmeta` | `assets/mystcraft/textures/blocks/portal.png` and `.mcmeta` | Legacy 0.13.7.06 local extraction | Byte-identical texture and line-ending-normalized animation metadata, used when Immersive Portals is absent |
 | `assets/rivencraft/sounds/linking/link-portal.ogg` | `assets/mystcraft/sounds/linking/link-portal.ogg` | Legacy 0.13.7.06 local extraction | Byte-identical portal-link sound |
+| `assets/rivencraft/sounds/linking/link-disarm.ogg` | `assets/mystcraft/sounds/linking/link-disarm.ogg` | Legacy 0.13.7.06 local extraction | Byte-identical disarm-link sound; takes precedence over the portal sound as in Legacy |
+| `assets/rivencraft/sounds/linking/link-intra.ogg` | `assets/mystcraft/sounds/linking/link-intra.ogg` | Legacy 0.13.7.06 local extraction | Byte-identical intra-link sound for Linking Books |
 
 Mystcraft Legacy identifies XCompWiz as its project developer and includes the
 full LGPL v3 text in its root `LICENSE` file. Rivencraft's root `LICENSE`

docs/GAMETESTS.md

@@ -85,8 +85,9 @@ With optional JEI installed, search for the Ink Mixer category. It should show
 the base paper/ink/vial operation and separate entries for Gunpowder, Mushroom
 Stew, Experience Bottle, Ender Pearl, Feather, and Fire Charge,
 with their property chances. Black Dye and Clay Ball should not appear: the
-former had no working Legacy effect, while Generate Platform is redundant
-with default Age arrival. Without JEI, Rivencraft should still
+former had no working Legacy effect, while Clay Ball remains unsupported by
+the mixer. The creative Link Modifier can enable a single arrival platform for
+Linking Books; they do not create one by default. Without JEI, Rivencraft should still
 start and the mixer should work normally.
 
 Put paper and an Ink Vial in the mixer. Hold Gunpowder on the cursor and

docs/INK_MIXER_MODIFIER_AUDIT.md

@@ -27,4 +27,4 @@ Implementation requirements: keep the mixer server-authoritative; persist mixtur
 
 The built-in vanilla-item rows above are supported except black dye and clay balls. Legacy ignores black dye's empty effect key, so Rivencraft does not consume or advertise it in JEI. Clay Balls are omitted because Age arrival already builds a safe platform by default and a separate Generate Platform link modifier would be redundant. Right-clicking the Ink Mixer basin with a carried item adds one; left-clicking adds the carried stack. The mixture is persistent and its next panel is deterministic. The visual basin tooltip shows current probabilities. Only taking the virtual Link Panel consumes paper/ink and clears the mixture. The Link Panel's property component is copied to a Linking Book by the leather recipe or a Descriptive Book by the Binder. JEI's optional Ink Mixer category lists the base panel and each supported additive interaction with its per-property chance; Rivencraft does not require JEI to run.
 
-Disarm and Maintain Momentum are applied by the server after confirming a safe destination. Disarm spawns each inventory stack as an item entity at the departure point, including for Descriptive Books. Intra Linking is required only for a Linking Book whose destination is in the player's current dimension; ordinary cross-dimensional Linking Books still work. The Binder treats an Intra Linking panel as an ordinary Link Panel and omits that flag from the resulting Descriptive Book, while retaining Disarm and Maintain Momentum. Automatic Return Links remain enabled under the existing configuration, as requested. The old Generate Platform bit remains readable on pre-0.4.7.1 test items but is neither rolled nor applied. Optional dust-tag mappings remain outside this built-in subset until their cross-mod tags and gameplay meaning are agreed.
+Disarm and Maintain Momentum are applied by the server after confirming a safe destination. Disarm spawns each inventory stack as an item entity at the departure point, including for Descriptive Books. Intra Linking is required only for a Linking Book whose destination is in the player's current dimension; ordinary cross-dimensional Linking Books still work. The Binder treats an Intra Linking panel as an ordinary Link Panel and omits that flag from the resulting Descriptive Book, while retaining Disarm and Maintain Momentum. Automatic Return Links remain enabled under the existing configuration, as requested. The Ink Mixer still does not roll Generate Platform, but since 0.6.7.1 the creative Link Modifier can explicitly enable it for Linking Books; their default remains off. Optional dust-tag mappings remain outside this built-in subset until their cross-mod tags and gameplay meaning are agreed.

docs/LEGACY_M7_AUDIT.md

@@ -15,9 +15,13 @@ Rivencraft has books, Ages, symbol writing, book stands, a desk, binder, Ink Mix
 
 ## Crystal portals: targets for #77–#78
 
-Issue #77 now has a craftable Book Receptacle (eight Crystal Blocks around an empty center), a bounded loaded-chunk crystal-network validator, persistent book holder/source pointers, animated Legacy portal cells, and portal collision routed through the existing Linking/Descriptive Book travel services. A book is only taken after a nonempty frame plan and destination dimension are validated. Removing the book or breaking its support removes the portal; a periodic server repair pass checks the loaded frame after restarts or edits. The Descriptive Book path preserves the configured automatic Return Link policy and link modifiers. Crystal-portal arrival does not generate a landing platform, matching Legacy's external travel semantics. A normal Linking Book still needs Intra Linking for same-dimension travel.
+Issue #77 now has a craftable Book Receptacle (eight Crystal Blocks around an empty center), a bounded loaded-chunk crystal-network validator, persistent book holder/source pointers, animated Legacy portal cells, and portal collision routed through the existing Linking/Descriptive Book travel services. A book is only taken after a nonempty frame plan and destination dimension are validated. Removing the book or breaking its support removes the portal; portal cells validate on neighboring block changes, like vanilla portals, rather than self-destructing on recurring ticks during chunk loading. The Descriptive Book path preserves the configured automatic Return Link policy and link modifiers. Crystal-portal arrival does not generate a landing platform, matching Legacy's external travel semantics. A normal Linking Book still needs Intra Linking for same-dimension travel.
 
-When Immersive Portals is present, render-only, non-teleporting IP portal entities show the book's destination through both faces of each coplanar opening; individual crystal cells are combined into one shaped surface so the destination is not repeated tile by tile. The view's central camera is aligned to the same safe arrival position and yaw/pitch used by book travel (at standing eye height). Perspective still changes naturally as the observer moves in front of a live portal. Each live view is recessed inside the opening; the fallback portal texture is always hidden while IP is installed, and crystal blocks render after the IP view so the frame appears on top. Without IP, the animated Legacy portal texture remains visible. Rivencraft portal-block contact remains the travel authority. This is an optional compile-only integration. The first placement of a Descriptive Book can generate/load its Age to establish a view destination. If the optional view is absent after restart, the holder's periodic pass recreates it. #78 retains exhaustive multiplayer, protection, destination deletion, and chunk-ticket hardening.
+When Immersive Portals is present, render-only, non-teleporting IP portal entities show the book's destination through both faces of each coplanar opening; individual crystal cells are combined into one shaped surface so the destination is not repeated tile by tile. The view's central camera is aligned to the same safe arrival position and yaw/pitch used by book travel (at standing eye height). Perspective still changes naturally as the observer moves in front of a live portal. Each live view is recessed inside the opening; the animated fallback texture stays visible until the live view is established, and crystal blocks render after the IP view so the frame appears on top. Without IP, the animated Legacy portal texture remains visible. Rivencraft portal-block contact remains the travel authority. This is an optional compile-only integration. The first placement of a Descriptive Book can generate/load its Age to establish a view destination. If the optional view is absent after restart, the holder's maintenance pass recreates it. Portal contact uses IP's instant transfer only if the destination's 3×3 chunk area was already loaded; otherwise it uses vanilla Minecraft's dimension transfer.
+
+Issue #78 hardening: placing each new portal cell fires a NeoForge entity-place protection event attributed to the player who inserted the book. If any cell is rejected, portal placement rolls back and the book remains with the player. Cells are placed without intermediate neighbor notifications so the frame validator cannot remove the first cells before the whole opening exists. Unattended maintenance never generates missing cells or tears down a saved portal during restart: block-change validation handles local frame damage, while the book remains retrievable. Portal owner positions are NBT integer arrays (not compound tags); the reader now matches that format, live-view state changes preserve the block entity's owner, and an intact saved surface with ownerless cells can recover its pointers from the adjacent book receptacle without placing new blocks. A missing neighboring chunk is treated as unknown, not as a broken frame. Portal cooldowns are per-player and session-only, never saved against a server tick counter that resets on restart. A Descriptive Book portal now searches for existing safe footing without creating a platform; Linking Books retain their intentionally floor-optional destination rule. Missing destination dimensions keep the book retrievable and remove any stale Immersive Portals view. Portal blocks and crystal frames are explicitly decay-protected. Book-GUI preview chunk loaders close on GUI exit, travel, logout, and server stop, with a five-minute fail-safe if a release packet is lost; crystal portals themselves add no Rivencraft chunk tickets.
+
+Manual #78 matrix (use two players where noted): restart with an active portal and confirm the book, surface, and destination view return once its chunk loads; walk through it immediately and after 10 seconds without reinserting the book. Then unload/reload the Age and repeat. With destination chunks loaded, contact should transfer instantly; with them unloaded, it should use Minecraft's normal dimension transfer while the animated fallback remains visible until the live view is ready. Have both players enter the same portal, return through separately bound books, and confirm each cooldown is independent and neither loops immediately. Test a Descriptive Book destination with unsafe feet/head space and with no existing footing: it must choose another footed spot or refuse travel, never generate a platform. Deny a portal cell with a block-protection mod and confirm activation consumes no book and leaves no partial surface. Break one cell and confirm it does not silently reappear. Remove or unload the destination dimension and confirm no crash or stale live view, while the book can still be retrieved. Open a book preview with Immersive Portals, close it, and confirm its temporary chunk loader is released; an abandoned preview should expire within five minutes. Repeat with Immersive Portals absent to confirm the fallback texture and book travel.
 
 Manual #77 check: build a 3×3 vertical Crystal Block ring, put the Receptacle on one frame crystal's outward face, then insert a bound Linking Book. The center should animate and link on contact; the book stays in the Receptacle. Confirm unbound books and incomplete frames do not consume items; empty-hand right-click retrieves the book and clears the surface. Repeat with a Descriptive Book and with Immersive Portals installed: the latter should show the destination live. Restart with the portal active and confirm the surface/view returns; break the support crystal and confirm book/portal cleanup.
 
@@ -42,13 +46,13 @@ For a manual check, create a fresh surface Age and run `/rivencraft library near
 
 Issue #75's comment calls this a despawning drop. The code differs subtly: [`EntityLinkbook`](https://github.com/Mystcraft/Mystcraft-Legacy/blob/9bc8ddc061845df0cd5ea47f4fdef773cff786ae/src/main/java/com/xcompwiz/mystcraft/entity/EntityLinkbook.java#L190-L224) explicitly cannot despawn, but takes one starvation damage every 10,000 ticks and damage while wet. It can eventually be destroyed if left unattended; a vanilla item entity's fixed five-minute timeout is not parity. A modern equivalent should retain the visible book and avoid silently deleting its Age identity at that timeout.
 
-Legacy's travel path creates no automatic Return Link. Rivencraft currently defaults to `ON_CREATION` via `DescriptiveBookItem` and `descriptive_books.return_link_mode`. Per #75's comment, change the **new-config default** to `DISABLED` while retaining `ON_CREATION` and `ALWAYS` as opt-ins. Existing saved server configs must keep their explicit value. Handheld-book drop and Return Link default are tracked in [#85](https://truenas-scale.tail180fb1.ts.net:8443/dnorberg/rivencraft/issues/85), not portal-frame logic.
+Legacy's travel path creates no automatic Return Link. Rivencraft now defaults to `DISABLED` in new server configs while retaining `ON_CREATION` and `ALWAYS` as opt-ins. Existing saved server configs keep their explicit value. Issue #85 adds the active-book drop only to hand-held Linking and Descriptive Book travel. On a successful link, the exact active stack becomes a dedicated `DroppedBookEntity` at the departure point, rendered with the same open `BookModel` and textures as the book stand; a rejected link restores it to the original hand. Stand and portal use leave their books in place. The entity has unlimited vanilla lifetime and loses one of its five item-health points every 10,000 loaded ticks, plus one per wet tick, matching Legacy's slow/wet decay. Unlike Legacy's custom entity, the modern book is picked up by ordinary contact, not sneaking with an empty hand, and remains subject to ordinary item hazards. Following is not yet a Rivencraft modifier, so no Following exception is exposed or silently simulated. Both hands can activate a book, whereas Legacy's explicit stack removal tested only its selected main-hand slot.
 
 ## Crafting, sounds, and progression
 
 | Area | Legacy evidence and modern boundary |
 | --- | --- |
-| Crafting | [Legacy recipes](https://github.com/Mystcraft/Mystcraft-Legacy/tree/9bc8ddc061845df0cd5ea47f4fdef773cff786ae/src/main/resources/assets/mystcraft/recipes) specify the Receptacle, Binder, Mixer, Folder, Desk, and other writing blocks. [`RecipeLinkingbook`](https://github.com/Mystcraft/Mystcraft-Legacy/blob/9bc8ddc061845df0cd5ea47f4fdef773cff786ae/src/main/java/com/xcompwiz/mystcraft/data/RecipeLinkingbook.java#L28-L60) combines one Link Panel and leather anywhere in the grid. Rivencraft already has Binder, Mixer, Ink Vial, Notebook, Desk, Crystal Block, and Linking Book recipes. #79 adds only missing recipes/processes; preserve vanilla-Lectern conversion, noncraftable Blank Pages, and optional JEI. |
+| Crafting | [Legacy recipes](https://github.com/Mystcraft/Mystcraft-Legacy/tree/9bc8ddc061845df0cd5ea47f4fdef773cff786ae/src/main/resources/assets/mystcraft/recipes) specify the Receptacle, Binder, Mixer, Folder, Desk, and other writing blocks. [`RecipeLinkingbook`](https://github.com/Mystcraft/Mystcraft-Legacy/blob/9bc8ddc061845df0cd5ea47f4fdef773cff786ae/src/main/java/com/xcompwiz/mystcraft/data/RecipeLinkingbook.java#L28-L60) combines one Link Panel and leather anywhere in the grid. Rivencraft has Binder, Mixer, Ink Vial, Notebook, Desk, Crystal Block, Linking Book, and Receptacle recipes. #79 keeps these data-driven and adds recipe-book unlocks for Crystal Block, Receptacle, and Ink Vial. The Legacy potion-based ink variant is omitted: in 1.21.1 a simple potion ingredient does not return its glass bottle, while the existing water-bucket recipe returns its bucket. The Legacy Folder/Portfolio use Rivencraft's Notebook; the old two-part Desk is one item; the old Lectern/Book Stand recipes use a vanilla Lectern converted in-world by adding a Rivencraft book or page. Blank Pages remain noncraftable and Link Panels remain outside the Desk. JEI automatically displays the JSON crafting recipes; its existing optional categories cover Mixer, Desk, and Binder processes. The lectern interaction intentionally has no JEI guide. With Create installed, an optional Ponder scene attached to the Receptacle item demonstrates frame construction and book insertion; the core mod still runs without Create. |
 | Sounds | [`Sounds`](https://github.com/Mystcraft/Mystcraft-Legacy/blob/9bc8ddc061845df0cd5ea47f4fdef773cff786ae/src/main/java/com/xcompwiz/mystcraft/data/Sounds.java#L8-L26) registers pop, link, disarm, following, intra-link, fissure-link, portal-link, and meteor roar. The matching OGGs are in the local extraction. Rivencraft already carries link, fissure-link, and meteor roar. #80 should reuse and credit available Legacy files before creating alternatives. |
 | Advancements | [Legacy advancement JSONs](https://github.com/Mystcraft/Mystcraft-Legacy/tree/9bc8ddc061845df0cd5ea47f4fdef773cff786ae/src/main/resources/assets/mystcraft/advancements) have inventory milestones for a symbol page, unlinked Linking Book, and Age Book; a Writing Desk trigger; a safe Age-travel trigger; and a hidden Quinn trigger. #81 should use modern server-owned criteria. Quinn has no established Rivencraft equivalent and should be documented or deliberately omitted, not awarded on preview. |
 

docs/MILESTONE_7_ADVANCEMENTS.md

@@ -0,0 +1,40 @@
+# Milestone 7 advancements and discovery (#81)
+
+Rivencraft's advancement tab follows the visible progression in Mystcraft
+Legacy's `assets/mystcraft/advancements/`: Page, unwritten Linking Book,
+Writing Desk writing, Age Book, and safe Age travel. Titles such as *The Ending
+Has Not Yet Been Written*, *D'ni Ink*, and *The Art of Writing* reference Myst
+without requiring any assets from that game. The Legacy hidden Quinn trigger
+has no established Rivencraft action and is deliberately omitted.
+
+`root`, `page`, and `linking_book` use vanilla server-side tick/inventory
+criteria. `link_panel`, `copy_page`, `bind_age`, `open_portal`, and `enter_age`
+use an impossible criterion awarded only after the server commits the
+corresponding action. The Age-travel award requires a successful book or portal
+link ending in a registered Rivencraft Age. Opening a book GUI, rendering a
+destination preview, viewing a recipe, or merely loading an Age cannot award
+it. Progress is stored by Minecraft per player and survives world restarts.
+
+Vanilla recipe-book unlock advancements now cover the Writing Desk, Ink Mixer,
+Book Binder, and Notebook, in addition to the existing Ink Vial, Crystal
+Block, and Book Receptacle unlocks. The component-sensitive Linking Book
+crafting recipe remains a special recipe: its Link Panel requirement and the
+Writing Desk/Ink Mixer/Book Binder processes are explained by Rivencraft's
+optional JEI integration. No recipe or advancement requires JEI, Create, or
+Immersive Portals to be installed.
+
+Manual Survival check: collect a Page and Linking Book; use the Ink Mixer to
+take a Link Panel; copy a Page at the Writing Desk; bind a Descriptive Book;
+enter its Age; activate a Crystal Portal. Confirm each advancement appears
+only after the completed action, not from an output preview or GUI opening.
+Repeat the actions with two players to confirm only the actor receives each
+award. Restart an existing save and confirm completed progress remains, then
+complete one previously unearned milestone. With JEI absent, the vanilla
+recipe book should still reveal standard crafting recipes as their ingredients
+are discovered; with JEI installed, the special writing guides should appear.
+
+The automated Book Binder output-award scenario stalls in the GameTest storage
+runner, so it is intentionally omitted under the project test policy. For its
+manual check, open a ready Binder, observe that merely previewing the finished
+book does not award *A Book of Ages*, then take the book and confirm the award.
+Repeat by shift-clicking the result in a fresh Binder.

docs/MILESTONE_7_COMPATIBILITY_REVIEW.md

@@ -0,0 +1,53 @@
+# Milestone 7 compatibility review (#82)
+
+Reviewed 2026-10-19 for Minecraft 1.21.1. The project now compiles against
+NeoForge 21.1.264 and advertises that as its minimum. The official
+[NeoForge Maven metadata](https://maven.neoforged.net/releases/net/neoforged/neoforge/maven-metadata.xml)
+lists 21.1.264 as the newest 21.1 release. Its
+[changelog](https://maven.neoforged.net/releases/net/neoforged/neoforge/21.1.264/neoforge-21.1.264-changelog.txt)
+includes received split-packet size checks (21.1.260), network setup payload
+direction/decoding limits (21.1.261), ad-hoc channel identifier limits
+(21.1.262), and an initial attachment-sync fix (21.1.264). Those are concrete
+reasons to evaluate an upgrade, but do not by themselves prove Rivencraft and
+its optional integrations work on that loader.
+
+**Decision: adopt 21.1.264 beginning with 0.6.6.2.** An override build
+succeeded, but its GameTest server repeated its storage-progress display
+without producing test results. That run was stopped; it is neither a pass nor
+evidence of a NeoForge defect. The player subsequently passed an in-game
+singleplayer test on 21.1.264 with the optional stack, then passed a dedicated
+server test including Immersive Portals travel to a Rivencraft Age. The
+dedicated server also reached the ready state with only the required mods
+before the full optional stack was installed. Both modes used Rivencraft
+0.6.6.1. The earlier 21.1.251 baseline passed 70 required GameTests for
+release V0.6.6.0.
+
+| Dependency | Project baseline | Newest checked 1.21.1 release | Follow-up |
+| --- | --- | --- | --- |
+| Dynamic Dimensions AR Edition (required) | 0.9.1 | 0.9.1 | No newer release found on [CurseForge](https://www.curseforge.com/minecraft/mc-mods/dynamicdimension-ar-edition/files/all). |
+| Bad Packets (required) | neo-0.8.2 | neo-0.8.2 | No newer matching [Modrinth](https://modrinth.com/mod/badpackets/versions) release found. |
+| JEI (optional) | 19.57.0.449 at #82 review | 19.69.0.457 beta | Updated in #86 after client and dedicated GameTest passes; see [JEI review](MILESTONE_7_JEI_REVIEW.md). |
+| Create (optional) | 6.0.10 | 6.0.10 | No newer matching [Modrinth](https://modrinth.com/mod/create/versions) release found. Its jar bundles Ponder 1.0.82. |
+| Ponder (bundled with Create) | 1.0.82 | 1.0.87 library artifact | [Maven](https://maven.createmod.net/net/createmod/ponder/ponder-neoforge/maven-metadata.xml) has a newer artifact, but Create 6.0.10 still bundles 1.0.82. Do not treat this as a separately installed Create update. |
+| Immersive Portals (optional) | 6.0.7 | 6.0.7 | No newer matching [Modrinth](https://modrinth.com/mod/immersive-portals-neoforge/versions) release found. |
+| TerraBlender (optional) | 4.1.0.8 | 4.1.0.8 | No newer matching [Modrinth](https://modrinth.com/mod/terrablender/versions) release found. |
+| Serene Seasons (optional) | 10.1.0.8 at #82 review | 10.1.0.9 | Updated in #88 after the player's full seasonal matrix passed; see [Serene review](MILESTONE_7_SERENE_REVIEW.md). |
+| GlitchCore (Serene dependency) | 2.1.0.2 | 2.1.0.2 | No newer matching [Modrinth](https://modrinth.com/mod/glitchcore/versions) release found. |
+| Biomes O' Plenty (TerraBlender test addon) | 21.1.0.14 in user's Prism instance | 21.1.0.14 | No newer matching [Modrinth](https://modrinth.com/mod/biomes-o-plenty/versions) release found. |
+
+The Modrinth version comparisons above were filtered to **NeoForge and
+Minecraft 1.21.1** on 2026-10-19. Create's bundled Ponder version was read
+from `META-INF/jarjar/metadata.json` in `create-1.21.1-6.0.10.jar`; the
+separate library-artifact comparison came from Create's Maven. Dynamic
+Dimensions was checked on CurseForge. Versions for other Minecraft lines and
+similarly named mods were excluded.
+
+The full dedicated test stack contained Create/Ponder, Immersive Portals, JEI,
+TerraBlender with Biomes O' Plenty, and Serene Seasons with GlitchCore. The
+server loaded a new `rivencraft:age/test`, and its shutdown log confirms that
+all Overworld, Nether, End, and Age chunks were saved. The player explicitly
+approved 21.1.264 after that test. This does not independently certify every
+optional combination, the LEGACY preview fallback on a client without Create
+and Immersive Portals, or a full restart/rejoin cycle; keep those in the
+regression checklist. Serene's GameTest mock-player network limitation still
+requires real-client checks for seasonal behavior.

docs/MILESTONE_7_JEI_REVIEW.md

@@ -0,0 +1,41 @@
+# JEI compatibility review (#86)
+
+Reviewed 2026-10-20 for Minecraft 1.21.1 and NeoForge 21.1.264. Rivencraft
+now targets JEI 19.69.0.457 after the client's in-game acceptance check. JEI
+remains a `compileOnly` API and an opt-in
+`localRuntime` dependency for development; the published mod has no required
+JEI dependency.
+
+The [official 1.21.1 NeoForge files](https://www.curseforge.com/minecraft/mc-mods/jei/files/all?page=1&pageSize=20&version=1.21.1)
+list 19.69.0.457 (beta, 2026-10-20) after 19.64.0.455 (release, 2026-10-16).
+The [19.69.0.457 Modrinth changelog](https://modrinth.com/mod/jei/versions?g=1.21.1&l=neoforge)
+has a published-jar bytecode compatibility check. Its preceding 19.69.0.456
+build changes ingredient search to Lucene and adds a runtime ingredient-search
+refresh API. This makes page search a required client check, even though the
+current Rivencraft plugin still compiles against the 457 API. The new Maven
+runtime artifact is much larger (about 7 MB versus 2.3 MB for 455); a successful
+compile alone is not evidence that its runtime plugin works.
+
+Checks performed before changing the pinned dependency:
+
+| Configuration | Result |
+| --- | --- |
+| `./gradlew -Pjei_version=19.69.0.457 -PwithJei=true build` | Passed; existing JEI API uses compile with four deprecation warnings and no errors. |
+| `./gradlew -Pjei_version=19.69.0.457 -PwithJei=true runGameTestServer` | Passed; dedicated GameTest server loaded JEI 19.69.0.457 and all 74 required tests passed. |
+| `./gradlew -Pjei_version=19.69.0.457 runGameTestServer` | Passed without JEI; all 74 required tests passed. |
+| Prism client with JEI 19.69.0.457 and Rivencraft 0.6.6.6 | Client joined an integrated world; JEI registered Rivencraft extra ingredients and started without a JEI-plugin exception. The player reported an in-game pass for guide display, page search, and recipe visibility. |
+
+On first 457 launch, JEI migrated its old `lowMemorySlowSearchEnabled` config
+key and saved a backup of the original `jei-client.ini`; that warning was
+handled by JEI and did not block startup. No Rivencraft config was changed.
+
+The in-game acceptance report covers the visible JEI integration. A dedicated
+GameTest server proves no server-side startup failure but does not exercise the
+JEI GUI; keep page search, recipes, blank-Page hiding, and the Ink Mixer,
+Writing Desk, and Book Binder guides in future upgrade checks. JEI is not
+bundled into or required by the published Rivencraft jar.
+
+The final pinned `0.6.6.7` build passed. A repeat GameTest run from the pinned
+configuration stalled during test-world preparation before running any cases;
+it was stopped. The two successful pre-pin runs above used the same JEI version
+and code, with the dependency supplied by a Gradle property override.

docs/MILESTONE_7_SERENE_REVIEW.md

@@ -0,0 +1,31 @@
+# Serene Seasons 10.1.0.9 compatibility review (#88)
+
+Reviewed 2026-10-20 for Minecraft 1.21.1 and NeoForge 21.1.264. Rivencraft
+now compiles against [Serene Seasons 10.1.0.9](https://modrinth.com/mod/serene-seasons/version/pHEgQQUE)
+with [GlitchCore 2.1.0.2](https://modrinth.com/mod/glitchcore/version/S2TfWrZR).
+Both remain optional. The Serene update fixes a precipitation-mixin recursion;
+it does not introduce a new dynamic-dimension API.
+
+The 10.1.0.8 and 10.1.0.9 bytecode for Rivencraft's version-sensitive
+`SeasonsConfig`, `SeasonHandler`, `SeasonSavedData`, and `SeasonTime` integration
+classes is identical. In particular, the dimension whitelist field, per-level
+saved season clock, and season update method have unchanged signatures and
+implementations. The adapter still writes the whitelist through GlitchCore's
+config API and sends Rivencraft's whitelist update to already connected clients.
+
+Verification:
+
+| Check | Result |
+| --- | --- |
+| Build against 10.1.0.9 and GlitchCore 2.1.0.2 | Passed. |
+| Real Prism client with Serene 10.1.0.9, GlitchCore 2.1.0.2, and Rivencraft 0.6.6.7 | Both mods loaded and the player joined an Age. |
+| No Seasons, normal Seasons, and all four Eternal modes in new and saved Ages | Player reported the full in-game matrix passed. |
+| Reconnect, restart, and Overworld independence | Player reported the full in-game matrix passed. |
+| Isolated dedicated-server startup without Serene/GlitchCore | Reached `Done` on port 25568 with only required runtime mods, then saved and stopped. |
+| Isolated dedicated-server startup with Serene/GlitchCore | Reached `Done` on port 25569 with 10.1.0.9/2.1.0.2, then saved and stopped. |
+
+Serene's sync packet is incompatible with GameTest mock players, so its
+in-game behavior must be checked with a real client and server. The seasonal
+test path in [SERENE_SEASONS_COMPATIBILITY.md](SERENE_SEASONS_COMPATIBILITY.md)
+remains the regression checklist for future upgrades. Rivencraft does not
+bundle or require Serene Seasons or GlitchCore.

docs/MILESTONE_7_VISUAL_AUDIT.md

@@ -0,0 +1,63 @@
+# Milestone 7 visual and audio polish (#80)
+
+The source is the local Mystcraft 0.13.7.06 extraction under
+`/home/dnorberg/Documents/mystcraft-src/mystcraft-1.12.2-0.13.7.06/`.
+Reused textures and OGG files are recorded in [asset provenance](ASSET_PROVENANCE.md).
+The `dev images/book binder.png` and `dev images/ink mixer.png` screenshots
+are the Legacy model references used for this slice.
+
+## Legacy comparison and modern boundary
+
+- The Crystal Block, Book Receptacle, and 16×512 portal animation already use
+  Legacy sprites. The Receptacle's 16×16×6 model already matches the Legacy
+  slab. The fallback portal now uses Legacy's four-pixel-deep, double-faced
+  `linkportal_ns.json` geometry, with the original animation; it declares a
+  translucent render layer and portal particle texture. The block remains
+  non-occluding. When Immersive Portals supplies a live view, the fallback
+  model is hidden, while the crystal frame is drawn over the view.
+- The Age arrival platform now reuses the same Legacy crystal tile as Crystal
+  Block. It is an opaque, occluding full block, while retaining its empty loot
+  table and unobtainable pick-block behavior. It has glass-like 0.3 hardness.
+  The old cloud sprite is unused and removed.
+- The Book Binder now includes the two inner braces and central press/book
+  piece omitted by the earlier model, using the existing byte-identical
+  Legacy textures. The Ink Mixer uses Legacy's `inkwell_model.json` geometry
+  and four original inkwell textures. A thin white paper surface replaces the
+  black paper appearance from the reference; the old simplified mixer tiles
+  are no longer used. The half-alpha glass atlas is intentionally rendered on
+  a cutout layer; its more opaque look passed the player's in-game check.
+- Legacy's link listener selects Disarm before a custom portal sound, then
+  Following, Intra Linking, and ordinary Link. Rivencraft has no Following
+  modifier yet, so it selects Disarm, portal, Intra Linking, or ordinary Link
+  in that order. The Disarm and Intra OGGs are byte-identical Legacy copies.
+- Legacy sends 50 small neutral link particles in roughly a one-by-two-block
+  region at both departure and arrival. Its fixed-function particle class is
+  not portable to 1.21.1. Rivencraft uses a one-shot burst of 50 vanilla Cloud
+  particles at both ends, emitted only after successful server-authoritative
+  travel. There is no continuous portal-particle loop in the inspected Legacy
+  `BlockLinkPortal` class, so the portal surface itself adds none.
+- The Legacy `textures/entity/linkbook.png` and `linking/pop.ogg` are inspected
+  but not copied in this slice. The custom dropped Linkbook entity is part of
+  #85; adding its assets before the entity exists would leave unused resources.
+  Library walls, shelves, chest, and webs use vanilla blocks in the template,
+  so there are no separate library art files to port.
+
+## Manual visual/audio check
+
+Use the same bound book in a held use and a Crystal Portal. Confirm the link
+particles and audio play at both ends, and the portal landing matches the book.
+Repeat with Disarm and Intra Linking panels to check the distinct sounds.
+Compare the fallback portal, crystal frame, and Receptacle with Immersive
+Portals absent; verify the animated surface is visible from both sides and
+does not expose caves or other geometry through solid blocks. With Immersive
+Portals installed, confirm the live view replaces only the fallback surface,
+the frame draws in front, and no fallback texture covers the live view.
+Create/Ponder is optional and must not affect either rendering path.
+Check a freshly generated arrival platform from above and below: the crystal
+tile should be opaque, break about as quickly as glass, and drop no block item.
+Compare the Book Binder press and Ink Mixer cup/glass against the `dev images`
+references; the mixer paper should appear white, and neither block should
+show missing-texture checkerboards or see-through-world artifacts.
+
+The player reported that the in-game visual and audio checks pass on 2026-10-19,
+including acceptance of the cutout glass appearance and current block sounds.

docs/PREVIEW_COMPATIBILITY.md

@@ -45,7 +45,7 @@ being captured in the preview.
 
 ## Supported combinations and upstream limits
 
-The compatibility baseline is Minecraft 1.21.1, NeoForge 21.1.251, Create
+The compatibility baseline is Minecraft 1.21.1, NeoForge 21.1.264, Create
 6.0.10, and Immersive Portals 6.0.7. Core Age generation and the `LEGACY`
 backend run without Create or Immersive Portals; the headless GameTest server
 uses that dependency-free path.

docs/SYMBOL_SEMANTICS.md

@@ -20,7 +20,7 @@ Milestone 5 issue #29 adds typed meaning to the existing data-pack symbol catalo
 
 `poem` is optional, client-safe artwork metadata: exactly four alphabetic words, ordered top, right, bottom, left. The client layers their glyphs from the shared Legacy component sheet at runtime. GUI thumbnails use the full transparent artwork over their page backgrounds; item icons use the same artwork reduced from 16 to 13 pixels across, over the page texture. Unregistered words use a stable generated component combination; when a symbol has no poem, the six original built-in IDs retain their Legacy poems and other IDs produce four stable fallback words. This affects appearance only, never Age generation. Generated images are cached up to 256 entries and discarded on resource reload.
 
-The Writing Desk's 88 collection tabs use Legacy's number components, chiefly the bottom row of `symbolcomponents.png`, rather than word sigils. Legacy's `ModWords.constructNumber` combines four unit marks (1–4) with four five-step marks (5–20) to form 1–24 and uses a separate zero mark. Rivencraft extends these marks positionally in base 25 for tabs 25–88 (for example, 25 is 1 followed by 0). Hovering still reveals the decimal number for accessibility. The former arbitrary-word glyph generator remains useful for rendering text: on page-free Descriptive Books, the generated Age description now appears as a sequence of layered word glyphs instead of Minecraft's enchantment font. The Age name stays readable.
+The Writing Desk retains 88 collection tabs, numbered from zero as in Legacy. Legacy's `ModWords.constructNumber` defines 0 as component 1 and 1–24 by overlaying a unit mark (1–4) and a five-step mark (5–20) from the bottom row of `symbolcomponents.png` in the *same square*. Legacy's Writing Desk has 25 tabs (0–24) and scrolls its four-tab window **one tab at a time**. Thus the supplied Legacy screenshots labeled 1–4, 5–8, and so on show overlapping windows, not 88 distinct numerals. Rivencraft retains its previously requested four-at-a-time navigation and 88 tabs. Its additional tab numbers use positional base 25: each place is an overlaid Legacy digit, with the places side by side (25 = 1,0). The two glyphs are sized and positioned to fit the tab. Hovering reveals the decimal tab index for accessibility. The generated-word mechanism renders page-free Descriptive Book text as layered glyphs instead of Minecraft's enchantment font. The Age name stays readable.
 
 | Role | Value type and allowed values |
 | --- | --- |

gradle.properties

@@ -18,11 +18,11 @@ minecraft_version=1.21.1
 # as they do not follow standard versioning conventions.
 minecraft_version_range=[1.21.1]
 # The Neo version must agree with the Minecraft version to get a valid artifact
-neo_version=21.1.251
+neo_version=21.1.264
 ponder_version=1.0.82
 dynamic_dimensions_file_id=7707789
 badpackets_version=0.8.2
-jei_version=19.57.0.449
+jei_version=19.69.0.457
 # The loader version range can only use the major version of FML as bounds
 loader_version_range=[1,)
 
@@ -36,10 +36,10 @@ mod_name=Rivencraft
 # The license of the mod. Review your options at https://choosealicense.com/. All Rights Reserved is the default.
 mod_license=LGPL-3.0-or-later
 # The mod version. Rivencraft uses the x.y.z.b policy documented in README.md.
-mod_version=0.6.2.5
+mod_version=0.6.8.7
 immersive_portals_version=6.0.7
 terrablender_version=4.1.0.8
-serene_seasons_version_id=B6nTjh4b
+serene_seasons_version_id=pHEgQQUE
 glitchcore_version_id=S2TfWrZR
 # The group ID for the mod. It is only important when publishing as an artifact to a Maven repository.
 # This should match the base package used for the mod sources.

src/main/java/net/dnorberg/rivencraft/Rivencraft.java

@@ -54,6 +54,7 @@ public final class Rivencraft {
         ModBiomeSources.register(modEventBus);
         ModChunkGenerators.register(modEventBus);
         ModBlocks.register(modEventBus);
+        net.dnorberg.rivencraft.registry.ModEntities.register(modEventBus);
         ModBlockEntities.register(modEventBus);
         ModItems.register(modEventBus);
         ModMenus.register(modEventBus);
@@ -76,6 +77,7 @@ public final class Rivencraft {
         NeoForge.EVENT_BUS.addListener(AgeCelestialAngleSync::onPlayerLoggedIn);
         NeoForge.EVENT_BUS.addListener(AgeCelestialAngleSync::onPlayerChangedDimension);
         NeoForge.EVENT_BUS.addListener(AgeLifecycleEvents::onPlayerLoggedOut);
+        NeoForge.EVENT_BUS.addListener(AgeLifecycleEvents::onServerTickPost);
         NeoForge.EVENT_BUS.addListener(AgeLifecycleEvents::onServerStopping);
         NeoForge.EVENT_BUS.addListener(AgeInstabilityRuntime::onServerStopping);
         NeoForge.EVENT_BUS.addListener(AgeEnvironmentalProviders::onServerStopping);

src/main/java/net/dnorberg/rivencraft/advancement/ProgressionAdvancements.java

@@ -0,0 +1,30 @@
+package net.dnorberg.rivencraft.advancement;
+
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.book.AgeRegistrySavedData;
+import net.minecraft.resources.ResourceLocation;
+import net.minecraft.server.level.ServerPlayer;
+
+/** Awards action-only progression after the server has committed the action. */
+public final class ProgressionAdvancements {
+    public static final String LINK_PANEL = "link_panel";
+    public static final String COPY_PAGE = "copy_page";
+    public static final String BIND_AGE = "bind_age";
+    public static final String OPEN_PORTAL = "open_portal";
+    public static final String ENTER_AGE = "enter_age";
+
+    private ProgressionAdvancements() {}
+
+    public static void award(ServerPlayer player, String path) {
+        var advancement = player.getServer().getAdvancements().get(
+                ResourceLocation.fromNamespaceAndPath(Rivencraft.MOD_ID, "progression/" + path));
+        if (advancement != null) player.getAdvancements().award(advancement, "completed");
+    }
+
+    public static void awardAgeTravel(ServerPlayer player) {
+        if (AgeRegistrySavedData.get(player.serverLevel()).findByDimension(
+                player.serverLevel().dimension().location()).isPresent()) {
+            award(player, ENTER_AGE);
+        }
+    }
+}

src/main/java/net/dnorberg/rivencraft/block/BookReceptacleBlock.java

@@ -1,5 +1,6 @@
 package net.dnorberg.rivencraft.block;
 
+import net.dnorberg.rivencraft.advancement.ProgressionAdvancements;
 import com.mojang.serialization.MapCodec;
 import net.dnorberg.rivencraft.block.entity.BookReceptacleBlockEntity;
 import net.dnorberg.rivencraft.portal.CrystalPortalNetwork;
@@ -76,7 +77,7 @@ public final class BookReceptacleBlock extends BaseEntityBlock {
     }
     @Override public BlockState getStateForPlacement(BlockPlaceContext context) {
         Direction face = context.getClickedFace();
-        if (face == Direction.DOWN || !context.getLevel().getBlockState(
+        if (!context.getLevel().getBlockState(
                 context.getClickedPos().relative(face.getOpposite())).is(ModBlocks.CRYSTAL_BLOCK.get())) return null;
         return defaultBlockState().setValue(FACING, face);
     }
@@ -96,7 +97,11 @@ public final class BookReceptacleBlock extends BaseEntityBlock {
         LinkTarget destination = stack.is(ModItems.LINKING_BOOK.get())
                 ? stack.get(ModDataComponents.LINK_TARGET.get())
                 : player instanceof ServerPlayer serverPlayer
-                    ? AgeDimensionService.resolve(serverPlayer, stack.get(ModDataComponents.AGE_REFERENCE.get())).orElse(null)
+                    ? AgeDimensionService.resolve(serverPlayer, stack.get(ModDataComponents.AGE_REFERENCE.get()),
+                            net.dnorberg.rivencraft.writing.OrderedWriting.EMPTY,
+                            !stack.getOrDefault(ModDataComponents.LINK_PROPERTIES.get(),
+                                    net.dnorberg.rivencraft.book.LinkProperties.NONE)
+                                    .has(net.dnorberg.rivencraft.book.LinkProperties.DISABLE_PLATFORM)).orElse(null)
                     : null;
         if (destination == null || server.getServer().getLevel(destination.location().dimension()) == null) {
             player.displayClientMessage(Component.translatable("message.rivencraft.descriptive_book.unavailable"), true);
@@ -104,14 +109,21 @@ public final class BookReceptacleBlock extends BaseEntityBlock {
         }
         holder.setBook(stack.copyWithCount(1));
         holder.setDestination(destination);
-        if (!CrystalPortalNetwork.activate(server, pos, plan)) {
+        if (!CrystalPortalNetwork.activate(server, pos, plan, player)) {
             holder.takeBook();
             return ItemInteractionResult.FAIL;
         }
         if (!player.getAbilities().instabuild) stack.shrink(1);
-        if (net.neoforged.fml.ModList.get().isLoaded("immersive_portals_core"))
-            net.dnorberg.rivencraft.compat.ImmersivePortalsCrystalView.activate(server, pos, plan, destination);
+        if (net.neoforged.fml.ModList.get().isLoaded("immersive_portals_core")) {
+            net.dnorberg.rivencraft.compat.ImmersivePortalsCrystalView.activate(server, pos, plan, destination,
+                    holder.getBook().is(ModItems.DESCRIPTIVE_BOOK.get()));
+            CrystalPortalNetwork.setLiveView(server, plan,
+                    net.dnorberg.rivencraft.compat.ImmersivePortalsCrystalView.complete(
+                            server, pos, plan, destination));
+        }
         level.playSound(null, pos, SoundEvents.ENCHANTMENT_TABLE_USE, SoundSource.BLOCKS, 1, 1);
+        if (player instanceof ServerPlayer serverPlayer)
+            ProgressionAdvancements.award(serverPlayer, ProgressionAdvancements.OPEN_PORTAL);
         return ItemInteractionResult.SUCCESS;
     }
 
@@ -132,7 +144,8 @@ public final class BookReceptacleBlock extends BaseEntityBlock {
     @Override protected void neighborChanged(BlockState state, Level level, BlockPos pos, Block neighbor,
             BlockPos neighborPos, boolean moved) {
         super.neighborChanged(state, level, pos, neighbor, neighborPos, moved);
-        if (!level.isClientSide && !level.getBlockState(pos.relative(state.getValue(FACING).getOpposite()))
+        BlockPos support = pos.relative(state.getValue(FACING).getOpposite());
+        if (!level.isClientSide && level.hasChunkAt(support) && !level.getBlockState(support)
                 .is(ModBlocks.CRYSTAL_BLOCK.get())) level.destroyBlock(pos, true);
     }
 

src/main/java/net/dnorberg/rivencraft/block/CloudPlatformBlock.java

@@ -1,14 +1,12 @@
 package net.dnorberg.rivencraft.block;
 
 import net.minecraft.core.BlockPos;
-import net.minecraft.core.Direction;
 import net.minecraft.world.item.ItemStack;
-import net.minecraft.world.level.BlockGetter;
 import net.minecraft.world.level.LevelReader;
 import net.minecraft.world.level.block.Block;
 import net.minecraft.world.level.block.state.BlockState;
 
-/** Solid footing for Age arrivals, rendered as a translucent cloud. */
+/** Solid crystal-textured footing for Age arrivals that cannot be collected. */
 public final class CloudPlatformBlock extends Block {
     public CloudPlatformBlock(Properties properties) {
         super(properties);
@@ -18,19 +16,4 @@ public final class CloudPlatformBlock extends Block {
     public ItemStack getCloneItemStack(LevelReader level, BlockPos pos, BlockState state) {
         return ItemStack.EMPTY;
     }
-
-    @Override
-    protected boolean skipRendering(BlockState state, BlockState adjacent, Direction side) {
-        return adjacent.is(this) || super.skipRendering(state, adjacent, side);
-    }
-
-    @Override
-    protected boolean propagatesSkylightDown(BlockState state, BlockGetter level, BlockPos pos) {
-        return true;
-    }
-
-    @Override
-    protected int getLightBlock(BlockState state, BlockGetter level, BlockPos pos) {
-        return 0;
-    }
 }

src/main/java/net/dnorberg/rivencraft/block/CrystalPortalBlock.java

@@ -3,17 +3,14 @@ package net.dnorberg.rivencraft.block;
 import com.mojang.serialization.MapCodec;
 import net.dnorberg.rivencraft.block.entity.BookReceptacleBlockEntity;
 import net.dnorberg.rivencraft.block.entity.CrystalPortalBlockEntity;
-import net.dnorberg.rivencraft.item.DescriptiveBookItem;
-import net.dnorberg.rivencraft.item.LinkingBookItem;
 import net.dnorberg.rivencraft.portal.CrystalPortalNetwork;
 import net.dnorberg.rivencraft.portal.PortalTravelCooldown;
+import net.dnorberg.rivencraft.portal.PortalTravelQueue;
 import net.dnorberg.rivencraft.registry.ModBlocks;
 import net.dnorberg.rivencraft.registry.ModItems;
 import net.minecraft.core.BlockPos;
 import net.minecraft.core.Direction;
-import net.minecraft.nbt.Tag;
 import net.minecraft.server.level.ServerLevel;
-import net.minecraft.server.level.ServerPlayer;
 import net.minecraft.util.RandomSource;
 import net.minecraft.world.entity.Entity;
 import net.minecraft.world.item.ItemStack;
@@ -35,7 +32,6 @@ public final class CrystalPortalBlock extends BaseEntityBlock {
     // Retained so portal blocks already saved with this state still deserialize.
     public static final BooleanProperty LIVE_VIEW = BooleanProperty.create("live_view");
     public static final EnumProperty<Direction.Axis> AXIS = EnumProperty.create("axis", Direction.Axis.class);
-    private static final String COOLDOWN = "RivencraftCrystalPortalCooldown";
 
     public CrystalPortalBlock(Properties properties) {
         super(properties);
@@ -46,10 +42,9 @@ public final class CrystalPortalBlock extends BaseEntityBlock {
         builder.add(LIVE_VIEW, AXIS);
     }
     @Override protected RenderShape getRenderShape(BlockState state) {
-        // The live-view flag can lag behind portal-entity creation or fail to
-        // synchronize for an existing frame. Never draw the fallback texture
-        // when Immersive Portals owns the view for this installation.
-        return ModList.get().isLoaded("immersive_portals_core")
+        // Keep the animated fallback until the optional destination view has
+        // actually been established, including after a world restart.
+        return ModList.get().isLoaded("immersive_portals_core") && state.getValue(LIVE_VIEW)
                 ? RenderShape.INVISIBLE : RenderShape.MODEL;
     }
     @Override public BlockEntity newBlockEntity(BlockPos pos, BlockState state) {
@@ -58,37 +53,32 @@ public final class CrystalPortalBlock extends BaseEntityBlock {
     @Override protected boolean canBeReplaced(BlockState state, Fluid fluid) { return false; }
 
     @Override protected void entityInside(BlockState state, Level level, BlockPos pos, Entity entity) {
-        if (!(level instanceof ServerLevel server) || !(entity instanceof ServerPlayer player)) return;
+        if (!(level instanceof ServerLevel server)) return;
         long now = server.getServer().getTickCount();
-        long previous = player.getPersistentData().contains(COOLDOWN, Tag.TAG_LONG)
-                ? player.getPersistentData().getLong(COOLDOWN) : -1;
-        if (previous > now) {
-            player.getPersistentData().remove(COOLDOWN);
-            previous = -1;
-        }
-        if (PortalTravelCooldown.blocked(now, previous)) return;
+        if (PortalTravelCooldown.blocked(entity, now)) return;
         if (!(level.getBlockEntity(pos) instanceof CrystalPortalBlockEntity portal)
                 || portal.receptacle() == null || !level.hasChunkAt(portal.receptacle())
                 || !(level.getBlockEntity(portal.receptacle()) instanceof BookReceptacleBlockEntity holder)) return;
         ItemStack book = holder.getBook();
         if (book.isEmpty()) return;
-        player.getPersistentData().putLong(COOLDOWN, now);
-        if (book.is(ModItems.LINKING_BOOK.get())) LinkingBookItem.usePortalBook(player, book);
-        else if (book.is(ModItems.DESCRIPTIVE_BOOK.get())) DescriptiveBookItem.usePortalBook(player, book);
+        PortalTravelCooldown.mark(entity, now);
+        PortalTravelQueue.enqueue(entity, server, pos, portal.receptacle(), book, now);
     }
 
     @Override protected void neighborChanged(BlockState state, Level level, BlockPos pos, Block neighbor,
             BlockPos neighborPos, boolean moved) {
         super.neighborChanged(state, level, pos, neighbor, neighborPos, moved);
-        if (level instanceof ServerLevel server) server.scheduleTick(pos, this, 2);
+        if (!(level instanceof ServerLevel server)
+                || !(level.getBlockEntity(pos) instanceof CrystalPortalBlockEntity portal)
+                || portal.receptacle() == null) return;
+        // Like a vanilla portal, validate when the frame changes, not on a
+        // repeating timer that can race block entities loading after restart.
+        if (CrystalPortalNetwork.cellStatus(server, pos, portal.receptacle())
+                == CrystalPortalNetwork.CellStatus.INVALID) server.removeBlock(pos, false);
     }
 
     @Override protected void tick(BlockState state, ServerLevel level, BlockPos pos, RandomSource random) {
-        if (!(level.getBlockEntity(pos) instanceof CrystalPortalBlockEntity portal)
-                || portal.receptacle() == null || !CrystalPortalNetwork.validCell(level, pos, portal.receptacle())) {
-            level.removeBlock(pos, false);
-            return;
-        }
-        level.scheduleTick(pos, this, 100);
+        // Ignore validation ticks saved by older builds. Frame edits are
+        // handled by neighborChanged, and the receptacle maintains the view.
     }
 }

src/main/java/net/dnorberg/rivencraft/block/LinkModifierBlock.java

@@ -0,0 +1,63 @@
+package net.dnorberg.rivencraft.block;
+
+import com.mojang.serialization.MapCodec;
+import net.dnorberg.rivencraft.block.entity.LinkModifierBlockEntity;
+import net.dnorberg.rivencraft.menu.LinkModifierMenu;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Direction;
+import net.minecraft.network.chat.Component;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.world.Containers;
+import net.minecraft.world.InteractionResult;
+import net.minecraft.world.SimpleMenuProvider;
+import net.minecraft.world.entity.player.Player;
+import net.minecraft.world.item.context.BlockPlaceContext;
+import net.minecraft.world.level.Level;
+import net.minecraft.world.level.block.BaseEntityBlock;
+import net.minecraft.world.level.block.RenderShape;
+import net.minecraft.world.level.block.entity.BlockEntity;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.block.state.StateDefinition;
+import net.minecraft.world.level.block.state.properties.BlockStateProperties;
+import net.minecraft.world.level.block.state.properties.DirectionProperty;
+import net.minecraft.world.phys.BlockHitResult;
+
+public final class LinkModifierBlock extends BaseEntityBlock {
+    public static final MapCodec<LinkModifierBlock> CODEC = simpleCodec(LinkModifierBlock::new);
+    public static final DirectionProperty FACING = BlockStateProperties.HORIZONTAL_FACING;
+
+    public LinkModifierBlock(Properties properties) {
+        super(properties);
+        registerDefaultState(stateDefinition.any().setValue(FACING, Direction.NORTH));
+    }
+
+    @Override protected MapCodec<? extends BaseEntityBlock> codec() { return CODEC; }
+    @Override protected void createBlockStateDefinition(StateDefinition.Builder<net.minecraft.world.level.block.Block,
+            BlockState> builder) { builder.add(FACING); }
+    @Override public BlockState getStateForPlacement(BlockPlaceContext context) {
+        return defaultBlockState().setValue(FACING, context.getHorizontalDirection().getOpposite());
+    }
+    @Override protected RenderShape getRenderShape(BlockState state) { return RenderShape.MODEL; }
+    @Override public BlockEntity newBlockEntity(BlockPos pos, BlockState state) {
+        return new LinkModifierBlockEntity(pos, state);
+    }
+    @Override protected InteractionResult useWithoutItem(BlockState state, Level level, BlockPos pos,
+                                                          Player player, BlockHitResult hit) {
+        if (!level.isClientSide && player instanceof ServerPlayer serverPlayer
+                && level.getBlockEntity(pos) instanceof LinkModifierBlockEntity modifier) {
+            serverPlayer.openMenu(new SimpleMenuProvider(
+                    (id, inventory, ignored) -> new LinkModifierMenu(id, inventory, modifier),
+                    Component.translatable("container.rivencraft.link_modifier")),
+                    buffer -> buffer.writeBlockPos(pos));
+        }
+        return InteractionResult.sidedSuccess(level.isClientSide);
+    }
+    @Override protected void onRemove(BlockState state, Level level, BlockPos pos,
+                                      BlockState replacement, boolean moving) {
+        if (!state.is(replacement.getBlock()) && !level.isClientSide
+                && level.getBlockEntity(pos) instanceof LinkModifierBlockEntity modifier) {
+            Containers.dropContents(level, pos, modifier);
+        }
+        super.onRemove(state, level, pos, replacement, moving);
+    }
+}

src/main/java/net/dnorberg/rivencraft/block/entity/BookBinderBlockEntity.java

@@ -12,6 +12,7 @@ import net.dnorberg.rivencraft.registry.ModBlockEntities;
 import net.dnorberg.rivencraft.registry.ModDataComponents;
 import net.dnorberg.rivencraft.registry.ModItems;
 import net.dnorberg.rivencraft.writing.NotebookContents;
+import net.dnorberg.rivencraft.item.CollationFolderItem;
 import net.dnorberg.rivencraft.writing.OrderedWriting;
 import net.dnorberg.rivencraft.writing.PageContent;
 import net.dnorberg.rivencraft.writing.WritingGrammar;
@@ -96,7 +97,7 @@ public final class BookBinderBlockEntity extends BlockEntity implements Containe
             case COVER -> validCover(stack);
             case LINK_PANEL -> stack.is(ModItems.PAGE.get())
                     && PageItem.content(stack).kind() == PageContent.Kind.LINK_PANEL;
-            case NOTEBOOK -> stack.is(ModItems.NOTEBOOK.get());
+            case NOTEBOOK -> CollationFolderItem.isCollection(stack);
             default -> slot >= FIRST_PAGE && slot < SIZE && validPage(stack);
         };
     }
@@ -296,7 +297,7 @@ public final class BookBinderBlockEntity extends BlockEntity implements Containe
 
     /** Import a Notebook from either its stored slot or the player's cursor. */
     public ItemStack importNotebookFromStack(ItemStack notebook, int index) {
-        if (!notebook.is(ModItems.NOTEBOOK.get()) || notebook.getCount() != 1) return ItemStack.EMPTY;
+        if (!CollationFolderItem.isCollection(notebook) || notebook.getCount() != 1) return ItemStack.EMPTY;
         List<ItemStack> pages = notebook.getOrDefault(ModDataComponents.NOTEBOOK_CONTENTS.get(), NotebookContents.EMPTY).pages();
         if (pages.isEmpty()) return ItemStack.EMPTY;
         int end = nextPageIndex();

src/main/java/net/dnorberg/rivencraft/block/entity/BookReceptacleBlockEntity.java

@@ -1,6 +1,7 @@
 package net.dnorberg.rivencraft.block.entity;
 
 import net.dnorberg.rivencraft.book.LinkTarget;
+import net.dnorberg.rivencraft.book.AgeEnvironmentCompiler;
 import net.dnorberg.rivencraft.registry.ModBlockEntities;
 import net.dnorberg.rivencraft.portal.CrystalPortalNetwork;
 import net.minecraft.nbt.NbtOps;
@@ -20,8 +21,11 @@ import net.neoforged.fml.ModList;
 public final class BookReceptacleBlockEntity extends BlockEntity {
     private static final String BOOK_TAG = "Book";
     private static final String DESTINATION_TAG = "Destination";
+    private static final String SKY_COLOR_TAG = "SkyColor";
     private ItemStack book = ItemStack.EMPTY;
     private LinkTarget destination;
+    private int skyColor = 0xFFFFFF;
+    private boolean restoreView = true;
 
     public BookReceptacleBlockEntity(BlockPos pos, BlockState state) {
         super(ModBlockEntities.BOOK_RECEPTACLE.get(), pos, state);
@@ -29,6 +33,7 @@ public final class BookReceptacleBlockEntity extends BlockEntity {
 
     public ItemStack getBook() { return book; }
     public LinkTarget destination() { return destination; }
+    public int skyColor() { return skyColor; }
 
     public void setBook(ItemStack stack) {
         book = stack.copyWithCount(1);
@@ -37,6 +42,12 @@ public final class BookReceptacleBlockEntity extends BlockEntity {
 
     public void setDestination(LinkTarget target) {
         destination = target;
+        skyColor = 0xFFFFFF;
+        if (target != null && level instanceof ServerLevel server) {
+            ServerLevel targetLevel = server.getServer().getLevel(target.location().dimension());
+            if (targetLevel != null) skyColor = AgeEnvironmentCompiler.previewSkyColor(
+                    targetLevel, target.location().pos()) & 0xFFFFFF;
+        }
         sync();
     }
 
@@ -44,6 +55,7 @@ public final class BookReceptacleBlockEntity extends BlockEntity {
         ItemStack result = book;
         book = ItemStack.EMPTY;
         destination = null;
+        skyColor = 0xFFFFFF;
         sync();
         return result;
     }
@@ -62,6 +74,8 @@ public final class BookReceptacleBlockEntity extends BlockEntity {
                 : ItemStack.EMPTY;
         destination = tag.contains(DESTINATION_TAG)
                 ? LinkTarget.CODEC.parse(NbtOps.INSTANCE, tag.get(DESTINATION_TAG)).result().orElse(null) : null;
+        skyColor = tag.contains(SKY_COLOR_TAG) ? tag.getInt(SKY_COLOR_TAG) & 0xFFFFFF : 0xFFFFFF;
+        restoreView = true;
     }
 
     @Override
@@ -70,6 +84,7 @@ public final class BookReceptacleBlockEntity extends BlockEntity {
         if (!book.isEmpty()) tag.put(BOOK_TAG, book.save(registries));
         if (destination != null) LinkTarget.CODEC.encodeStart(NbtOps.INSTANCE, destination)
                 .result().ifPresent(encoded -> tag.put(DESTINATION_TAG, encoded));
+        if (destination != null) tag.putInt(SKY_COLOR_TAG, skyColor);
     }
 
     @Override public Packet<ClientGamePacketListener> getUpdatePacket() {
@@ -83,13 +98,38 @@ public final class BookReceptacleBlockEntity extends BlockEntity {
     public static void serverTick(net.minecraft.world.level.Level world, BlockPos pos, BlockState state,
                                   BookReceptacleBlockEntity holder) {
         if (!(world instanceof ServerLevel level)) return;
-        if (level.getGameTime() % 200 != 0 || holder.book.isEmpty()) return;
-        CrystalPortalNetwork.reconcile(level, pos);
-        if (holder.destination == null || !ModList.get().isLoaded("immersive_portals_core")) return;
-        if (!net.dnorberg.rivencraft.compat.ImmersivePortalsCrystalView.exists(level, pos)) {
-            CrystalPortalNetwork.Plan plan = CrystalPortalNetwork.plan(level, pos);
-            if (plan.valid()) net.dnorberg.rivencraft.compat.ImmersivePortalsCrystalView.activate(
-                    level, pos, plan, holder.destination);
+        if (holder.book.isEmpty() || (!holder.restoreView && level.getGameTime() % 200 != 0)) return;
+        // Startup maintenance must never turn a saved portal off while its
+        // chunks and block entities are still arriving. Structural edits are
+        // validated by the portal blocks' neighbor updates instead.
+        if (holder.restoreView) CrystalPortalNetwork.recoverSavedOwners(level, pos);
+        CrystalPortalNetwork.Plan plan = CrystalPortalNetwork.plan(level, pos);
+        if (!plan.valid()) return;
+        if (!ModList.get().isLoaded("immersive_portals_core")) {
+            holder.restoreView = false;
+            return;
         }
+        if (holder.restoreView) CrystalPortalNetwork.setLiveView(level, plan, false);
+        holder.restoreView = false;
+        if (holder.destination == null) {
+            net.dnorberg.rivencraft.compat.ImmersivePortalsCrystalView.remove(level, pos);
+            CrystalPortalNetwork.setLiveView(level, plan, false);
+            return;
+        }
+        if (level.getServer().getLevel(holder.destination.location().dimension()) == null) {
+            net.dnorberg.rivencraft.compat.ImmersivePortalsCrystalView.remove(level, pos);
+            CrystalPortalNetwork.setLiveView(level, plan, false);
+            return;
+        }
+        if (!net.dnorberg.rivencraft.compat.ImmersivePortalsCrystalView.complete(
+                level, pos, plan, holder.destination)) {
+            CrystalPortalNetwork.setLiveView(level, plan, false);
+            net.dnorberg.rivencraft.compat.ImmersivePortalsCrystalView.activate(
+                    level, pos, plan, holder.destination,
+                    holder.book.is(net.dnorberg.rivencraft.registry.ModItems.DESCRIPTIVE_BOOK.get()));
+        }
+        CrystalPortalNetwork.setLiveView(level, plan,
+                net.dnorberg.rivencraft.compat.ImmersivePortalsCrystalView.complete(
+                        level, pos, plan, holder.destination));
     }
 }

src/main/java/net/dnorberg/rivencraft/block/entity/CrystalPortalBlockEntity.java

@@ -31,8 +31,7 @@ public final class CrystalPortalBlockEntity extends BlockEntity {
     @Override
     protected void loadAdditional(CompoundTag tag, HolderLookup.Provider registries) {
         super.loadAdditional(tag, registries);
-        receptacle = tag.contains(SOURCE_TAG, CompoundTag.TAG_COMPOUND)
-                ? net.minecraft.nbt.NbtUtils.readBlockPos(tag, SOURCE_TAG).orElse(null) : null;
+        receptacle = net.minecraft.nbt.NbtUtils.readBlockPos(tag, SOURCE_TAG).orElse(null);
     }
 
     @Override

src/main/java/net/dnorberg/rivencraft/block/entity/LinkModifierBlockEntity.java

@@ -0,0 +1,63 @@
+package net.dnorberg.rivencraft.block.entity;
+
+import net.dnorberg.rivencraft.registry.ModBlockEntities;
+import net.dnorberg.rivencraft.registry.ModItems;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.HolderLookup;
+import net.minecraft.core.NonNullList;
+import net.minecraft.nbt.CompoundTag;
+import net.minecraft.world.Container;
+import net.minecraft.world.ContainerHelper;
+import net.minecraft.world.entity.player.Player;
+import net.minecraft.world.item.ItemStack;
+import net.minecraft.world.level.block.entity.BlockEntity;
+import net.minecraft.world.level.block.state.BlockState;
+
+/** One persisted book slot; edits are performed by the server menu. */
+public final class LinkModifierBlockEntity extends BlockEntity implements Container {
+    private NonNullList<ItemStack> items = NonNullList.withSize(1, ItemStack.EMPTY);
+
+    public LinkModifierBlockEntity(BlockPos pos, BlockState state) {
+        super(ModBlockEntities.LINK_MODIFIER.get(), pos, state);
+    }
+
+    @Override public int getContainerSize() { return 1; }
+    @Override public boolean isEmpty() { return items.getFirst().isEmpty(); }
+    @Override public ItemStack getItem(int slot) { return items.get(slot); }
+    @Override public ItemStack removeItem(int slot, int amount) {
+        ItemStack removed = ContainerHelper.removeItem(items, slot, amount);
+        if (!removed.isEmpty()) setChanged();
+        return removed;
+    }
+    @Override public ItemStack removeItemNoUpdate(int slot) {
+        ItemStack removed = ContainerHelper.takeItem(items, slot);
+        if (!removed.isEmpty()) setChanged();
+        return removed;
+    }
+    @Override public void setItem(int slot, ItemStack stack) {
+        items.set(slot, stack.copyWithCount(Math.min(1, stack.getCount())));
+        setChanged();
+    }
+    @Override public boolean canPlaceItem(int slot, ItemStack stack) {
+        return slot == 0 && (stack.is(ModItems.LINKING_BOOK.get())
+                || stack.is(ModItems.DESCRIPTIVE_BOOK.get()));
+    }
+    @Override public boolean stillValid(Player player) {
+        return level != null && level.isLoaded(worldPosition) && level.getBlockEntity(worldPosition) == this
+                && player.distanceToSqr(worldPosition.getX() + 0.5, worldPosition.getY() + 0.5,
+                        worldPosition.getZ() + 0.5) <= 64.0;
+    }
+    @Override public void clearContent() {
+        items = NonNullList.withSize(1, ItemStack.EMPTY);
+        setChanged();
+    }
+    @Override protected void loadAdditional(CompoundTag tag, HolderLookup.Provider registries) {
+        super.loadAdditional(tag, registries);
+        items = NonNullList.withSize(1, ItemStack.EMPTY);
+        ContainerHelper.loadAllItems(tag, items, registries);
+    }
+    @Override protected void saveAdditional(CompoundTag tag, HolderLookup.Provider registries) {
+        super.saveAdditional(tag, registries);
+        ContainerHelper.saveAllItems(tag, items, registries);
+    }
+}

src/main/java/net/dnorberg/rivencraft/block/entity/WritingDeskBlockEntity.java

@@ -2,6 +2,7 @@ package net.dnorberg.rivencraft.block.entity;
 
 import net.dnorberg.rivencraft.item.InkVialItem;
 import net.dnorberg.rivencraft.item.PageItem;
+import net.dnorberg.rivencraft.item.CollationFolderItem;
 import net.dnorberg.rivencraft.writing.InkVialExchange;
 import net.dnorberg.rivencraft.writing.WritingInkService;
 import net.dnorberg.rivencraft.writing.PageContent;
@@ -87,7 +88,7 @@ public final class WritingDeskBlockEntity extends BlockEntity implements Contain
                         worldPosition.getZ() + 0.5) <= 64.0;
     }
     @Override public boolean canPlaceItem(int slot, ItemStack stack) {
-        if (slot < COLLECTIONS) return stack.is(ModItems.NOTEBOOK.get())
+        if (slot < COLLECTIONS) return CollationFolderItem.isCollection(stack)
                 && stack.getOrDefault(ModDataComponents.NOTEBOOK_CONTENTS.get(), NotebookContents.EMPTY)
                         .pages().stream().noneMatch(page -> PageItem.content(page).kind() == PageContent.Kind.LINK_PANEL)
                 || stack.is(ModItems.PAGE.get())

src/main/java/net/dnorberg/rivencraft/book/AgeDefinition.java

@@ -28,7 +28,8 @@ public record AgeDefinition(
     public static final ResourceLocation RANDOM_VANILLA_PROFILE = ResourceLocation.fromNamespaceAndPath(
             Rivencraft.MOD_ID, "random_vanilla"
     );
-    public static final int CURRENT_GENERATION_VERSION = 16;
+    public static final int LEGACY_GENERATOR_CUTOFF = 16;
+    public static final int CURRENT_GENERATION_VERSION = AgeSkyProfile.RANDOM_SKY_GENERATION_VERSION;
 
     public AgeDefinition {
         Objects.requireNonNull(id, "id");
@@ -118,4 +119,10 @@ public record AgeDefinition(
                 createdGameTime, dimensionId, spawn.immutable(), traits, plan, seasonMode,
                 randomFeatures, instability, instabilityPlan);
     }
+
+    /** A frozen authored profile takes precedence over the profile ID on old books. */
+    public boolean caveTerrain() {
+        return AgeBiomeSelection.isCave(plan == null
+                ? AgeRuntimeProfiles.resolve(generationProfile) : plan.runtimeProfile());
+    }
 }

src/main/java/net/dnorberg/rivencraft/book/AgeDeletionService.java

@@ -0,0 +1,56 @@
+package net.dnorberg.rivencraft.book;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.LinkOption;
+import java.nio.file.Path;
+import java.nio.file.StandardCopyOption;
+import java.nio.file.AtomicMoveNotSupportedException;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.minecraft.server.MinecraftServer;
+import net.minecraft.world.level.storage.LevelResource;
+
+/** Retires an exact Age and moves its unloaded region data out of the live world. */
+public final class AgeDeletionService {
+    public enum Result { RETIRED, ALREADY_DEAD, OCCUPIED, UNLOAD_FAILED, STORAGE_FAILED }
+
+    private AgeDeletionService() { }
+
+    public static Result retire(MinecraftServer server, AgeDefinition age) {
+        AgeRegistrySavedData registry = AgeRegistrySavedData.get(server.overworld());
+        if (registry.isDead(age.id())) return Result.ALREADY_DEAD;
+        var level = server.getLevel(AgeDimensionService.dimensionKey(age));
+        if (level != null && !level.players().isEmpty()) return Result.OCCUPIED;
+        if (AgeDimensionService.unload(server, age) == AgeDimensionService.UnloadResult.FAILED)
+            return Result.UNLOAD_FAILED;
+
+        Path world = server.getWorldPath(LevelResource.ROOT).toAbsolutePath().normalize();
+        Path ageRoot = world.resolve("dimensions/rivencraft/age").normalize();
+        Path data = world.resolve("dimensions")
+                .resolve(age.dimensionId().getNamespace())
+                .resolve(age.dimensionId().getPath()).normalize();
+        // Exact Rivencraft Age only; never move the shared age/ directory.
+        if (!data.startsWith(ageRoot) || data.equals(ageRoot)
+                || !"rivencraft".equals(age.dimensionId().getNamespace())
+                || !age.dimensionId().getPath().startsWith("age/")) return Result.STORAGE_FAILED;
+        try {
+            if (Files.isSymbolicLink(world.resolve("dimensions"))
+                    || Files.isSymbolicLink(world.resolve("dimensions/rivencraft"))
+                    || Files.isSymbolicLink(ageRoot) || Files.isSymbolicLink(data)) return Result.STORAGE_FAILED;
+            if (Files.exists(data, LinkOption.NOFOLLOW_LINKS)) {
+                Path archive = world.getParent().resolve(world.getFileName() + "-retired-ages")
+                        .resolve(age.id().toString());
+                if (Files.exists(archive, LinkOption.NOFOLLOW_LINKS)) return Result.STORAGE_FAILED;
+                Files.createDirectories(archive.getParent());
+                try { Files.move(data, archive, StandardCopyOption.ATOMIC_MOVE); }
+                catch (AtomicMoveNotSupportedException exception) { Files.move(data, archive); }
+                Rivencraft.LOGGER.warn("Retired Age {} data moved from {} to {}", age.id(), data, archive);
+            }
+        } catch (IOException exception) {
+            Rivencraft.LOGGER.error("Cannot archive data for Age {}", age.id(), exception);
+            return Result.STORAGE_FAILED;
+        }
+        registry.markDead(age.id());
+        return Result.RETIRED;
+    }
+}

src/main/java/net/dnorberg/rivencraft/book/AgeDimensionService.java

@@ -74,6 +74,7 @@ public final class AgeDimensionService {
         DynamicDimensionLoadCallback.register((server, loader) -> {
             ServerLevel overworld = server.overworld();
             for (AgeDefinition age : AgeRegistrySavedData.get(overworld).definitions()) {
+                if (AgeRegistrySavedData.get(overworld).isDead(age.id())) continue;
                 if (!canLoadProfile(server, age)) continue;
                 ServerLevel level = loader.loadDynamicDimension(
                         age.dimensionId(),
@@ -95,8 +96,19 @@ public final class AgeDimensionService {
 
     public static Optional<LinkTarget> resolve(ServerPlayer player, AgeReference reference,
                                                 OrderedWriting writing) {
-        AgeDefinition definition = AgeRegistrySavedData.resolveOrCreate(player.serverLevel(), reference, writing);
-        ServerLevel level = ensureLoaded(player.getServer(), definition);
+        return resolve(player, reference, writing, true);
+    }
+
+    public static Optional<LinkTarget> resolve(ServerPlayer player, AgeReference reference,
+                                                OrderedWriting writing, boolean generatePlatform) {
+        return resolve(player.serverLevel(), reference, writing, generatePlatform);
+    }
+
+    public static Optional<LinkTarget> resolve(ServerLevel source, AgeReference reference,
+                                               OrderedWriting writing, boolean generatePlatform) {
+        AgeDefinition definition = AgeRegistrySavedData.resolveOrCreate(source, reference, writing);
+        if (AgeRegistrySavedData.get(source).isDead(definition.id())) return Optional.empty();
+        ServerLevel level = ensureLoaded(source.getServer(), definition);
         if (level == null) {
             return Optional.empty();
         }
@@ -104,7 +116,8 @@ public final class AgeDimensionService {
         BlockPos spawn = definition.spawn();
         if (spawn == null) {
             applyInitialCelestialPhase(level, definition);
-            spawn = createSafeSpawn(level, definition);
+            spawn = createSafeSpawn(level, definition, generatePlatform);
+            if (spawn == null) return Optional.empty();
             if (AgeFeatureSelection.resolved(definition.plan()).stream()
                     .anyMatch(choice -> choice.id().equals(AgeFeatureSelection.STAR_FISSURES))
                     || definition.randomFeatures().stream()
@@ -122,6 +135,7 @@ public final class AgeDimensionService {
     }
 
     public static ServerLevel ensureLoaded(MinecraftServer server, AgeDefinition definition) {
+        if (AgeRegistrySavedData.get(server.overworld()).isDead(definition.id())) return null;
         ResourceKey<Level> key = dimensionKey(definition);
         ServerLevel existing = server.getLevel(key);
         if (existing != null) {
@@ -170,6 +184,10 @@ public final class AgeDimensionService {
     }
 
     private static void applyCelestialClock(ServerLevel level, AgeDefinition age) {
+        if (age.caveTerrain()) {
+            level.setDayTimePerTick(1.0F);
+            return;
+        }
         if (age.traits().hasStoppedCelestialCycle()) {
             // NeoForge rejects an exact zero rate. The smallest positive float
             // never advances the integer clock during a practical world
@@ -198,6 +216,7 @@ public final class AgeDimensionService {
     }
 
     private static void applyInitialCelestialPhase(ServerLevel level, AgeDefinition age) {
+        if (age.caveTerrain()) return;
         long phaseTime = (long)(age.traits().celestialPhase() * Level.TICKS_PER_DAY);
         if (AgeEnvironmentCompiler.hasWrittenPhase(age.plan())) {
             // Legacy's Nadir is midnight, while vanilla day time zero is sunrise.
@@ -216,21 +235,24 @@ public final class AgeDimensionService {
         return ResourceKey.create(net.minecraft.core.registries.Registries.DIMENSION, definition.dimensionId());
     }
 
-    private static BlockPos createSafeSpawn(ServerLevel level, AgeDefinition age) {
+    private static BlockPos createSafeSpawn(ServerLevel level, AgeDefinition age, boolean generatePlatform) {
         BlockPos floorCenter;
-        if (age.generationProfile().equals(AgeGenerationProfiles.CAVE)) {
+        if (age.caveTerrain()) {
             // Cave Ages are enclosed. Searching from the world ceiling would
             // select or expose their roof, so begin with the floor beneath a
             // player standing at Y=64 and search downward from there.
             floorCenter = highestFootedSurface(level, CAVE_SPAWN_SEARCH_Y - 1)
-                    .orElseGet(() -> fallbackSpawnFloor(level));
+                    .orElseGet(() -> generatePlatform ? fallbackSpawnFloor(level) : null);
         } else if (isNetherStyle(level)) {
-            floorCenter = netherSpawnFloor(level);
+            floorCenter = generatePlatform ? netherSpawnFloor(level)
+                    : highestFootedSurface(level, CAVE_SPAWN_SEARCH_Y - 1).orElse(null);
         } else {
-            floorCenter = highestFootedSurface(level).orElseGet(() -> fallbackSpawnFloor(level));
+            floorCenter = highestFootedSurface(level).orElseGet(() -> generatePlatform ? fallbackSpawnFloor(level) : null);
         }
 
-        for (int x = -PLATFORM_RADIUS; x <= PLATFORM_RADIUS; x++) {
+        if (floorCenter == null) return null;
+
+        if (generatePlatform) for (int x = -PLATFORM_RADIUS; x <= PLATFORM_RADIUS; x++) {
             for (int z = -PLATFORM_RADIUS; z <= PLATFORM_RADIUS; z++) {
                 BlockPos floor = floorCenter.offset(x, 0, z);
                 level.setBlock(floor, ModBlocks.CLOUD_PLATFORM.get().defaultBlockState(), 2);
@@ -241,6 +263,11 @@ public final class AgeDimensionService {
         }
 
         BlockPos spawn = floorCenter.above();
+        if (!generatePlatform) {
+            var safe = LinkingService.resolveDestination(level, spawn, true);
+            if (safe.isEmpty()) return null;
+            spawn = BlockPos.containing(safe.get());
+        }
         level.setDefaultSpawnPos(spawn, 0.0F);
         return spawn;
     }
@@ -325,7 +352,7 @@ public final class AgeDimensionService {
                     server.registryAccess().lookupOrThrow(Registries.STRUCTURE_SET),
                     server.registryAccess().lookupOrThrow(Registries.PLACED_FEATURE)
             );
-            return age.generationVersion() < AgeDefinition.CURRENT_GENERATION_VERSION
+            return age.generationVersion() < AgeDefinition.LEGACY_GENERATOR_CUTOFF
                     ? new FlatLevelSource(settings) : new AgeFlatChunkGenerator(biomeSource, settings, features, age.seed(), libraryAgeSymbols);
         }
         if (profile.terrain() == AgeRuntimeProfile.Terrain.VOID) {
@@ -335,7 +362,7 @@ public final class AgeDimensionService {
                     List.of()
             );
             settings.updateLayers();
-            return age.generationVersion() < AgeDefinition.CURRENT_GENERATION_VERSION
+            return age.generationVersion() < AgeDefinition.LEGACY_GENERATOR_CUTOFF
                     ? new FlatLevelSource(settings) : new AgeFlatChunkGenerator(biomeSource, settings, features, age.seed(), libraryAgeSymbols);
         }
 
@@ -345,7 +372,7 @@ public final class AgeDimensionService {
         NoiseGeneratorSettings baseSettings = noiseSettings.getOrThrow(settingsKey).value();
         Holder<NoiseGeneratorSettings> settings = Holder.direct(withBiomeMaterialRules(baseSettings));
         boolean caveTerrain = AgeBiomeSelection.isCave(profile);
-        return age.generationVersion() < AgeDefinition.CURRENT_GENERATION_VERSION
+        return age.generationVersion() < AgeDefinition.LEGACY_GENERATOR_CUTOFF
                 ? new NoiseBasedChunkGenerator(biomeSource, settings)
                 : new AgeFeatureChunkGenerator(biomeSource, settings, features, age.seed(),
                         caveTerrain, caveTerrain ? TerraBlenderBiomes.nether(server.registryAccess()) : List.of(),
@@ -428,7 +455,7 @@ public final class AgeDimensionService {
             AgeDefinition age,
             AgeRuntimeProfile profile
     ) {
-        if (age.generationVersion() < AgeDefinition.CURRENT_GENERATION_VERSION) {
+        if (age.generationVersion() < AgeDefinition.LEGACY_GENERATOR_CUTOFF) {
             return legacyBiomeSource(server, age, profile);
         }
         AgeBiomeSelection selection = age.plan() != null && age.plan().biomeSelection() != null
@@ -531,7 +558,9 @@ public final class AgeDimensionService {
         DimensionType base = server.registryAccess().lookupOrThrow(Registries.DIMENSION_TYPE)
                 .getOrThrow(ResourceKey.create(Registries.DIMENSION_TYPE, profile.dimensionType())).value();
         AgeTraits.Lighting lighting = age.traits().lighting();
-        boolean hasSkyLight = base.hasSkyLight() && lighting != AgeTraits.Lighting.DARK;
+        AgeSkyProfile sky = AgeSkyProfile.forAge(age);
+        boolean hasSkyLight = (base.hasSkyLight() || !sky.bodies().isEmpty())
+                && lighting != AgeTraits.Lighting.DARK && !age.caveTerrain();
         float ambientLight = lighting == AgeTraits.Lighting.BRIGHT ? 0.25F : 0.0F;
         return new DimensionType(
                 base.fixedTime(),
@@ -546,7 +575,9 @@ public final class AgeDimensionService {
                 base.height(),
                 base.logicalHeight(),
                 base.infiniburn(),
-                AgeEnvironmentCompiler.skyEffects(age.plan(), base.effectsLocation()),
+                age.plan() == null && sky.custom()
+                        ? AgeEnvironmentCompiler.CUSTOM_SKY_EFFECTS
+                        : AgeEnvironmentCompiler.skyEffects(age.plan(), base.effectsLocation()),
                 ambientLight,
                 base.monsterSettings()
         );

src/main/java/net/dnorberg/rivencraft/book/AgeEnvironmentCompiler.java

@@ -2,21 +2,38 @@ package net.dnorberg.rivencraft.book;
 
 import net.dnorberg.rivencraft.writing.SymbolSemantics;
 import net.minecraft.resources.ResourceLocation;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.resources.ResourceKey;
 import net.minecraft.world.level.dimension.BuiltinDimensionTypes;
 
 /** Resolves written environment pages without changing the seeded page-free Age path. */
 public final class AgeEnvironmentCompiler {
+    public static final ResourceLocation CUSTOM_SKY_EFFECTS = ResourceLocation.fromNamespaceAndPath(
+            "rivencraft", "custom_sky");
     private AgeEnvironmentCompiler() {}
 
     public static AgeTraits apply(AgeGenerationPlan plan, AgeTraits seeded) {
         if (plan == null) return seeded;
+        AgeTraits applied;
         if (plan.version() >= 4) {
             AgeTraits base = applyLegacy(plan, seeded);
             CelestialWriting ordered = orderedCelestial(plan, seeded);
-            return new AgeTraits(base.biomeDistribution(), base.lighting(), base.weather(),
+            applied = new AgeTraits(base.biomeDistribution(), base.lighting(), base.weather(),
                     ordered.period(), base.celestialAngle(), ordered.phase());
+        } else {
+            applied = applyLegacy(plan, seeded);
         }
-        return applyLegacy(plan, seeded);
+        AgeSkyProfile.compile(plan, applied);
+        return forTerrain(applied, plan.runtimeProfile());
+    }
+
+    /** Cave terrain has no exposed weather or meaningful sky clock, even with authored pages. */
+    public static AgeTraits forTerrain(AgeTraits traits, AgeRuntimeProfile profile) {
+        if (!AgeBiomeSelection.isCave(profile)) return traits;
+        return new AgeTraits(traits.biomeDistribution(), traits.lighting(), AgeTraits.Weather.OFF,
+                1.0D, 0.0F, 0.0F);
     }
 
     /** Version-3 plans keep their frozen, stage-sorted environment interpretation. */
@@ -57,8 +74,7 @@ public final class AgeEnvironmentCompiler {
                     phaseDegrees = writtenPhase ? circularMidpoint(phaseDegrees, next) : next;
                     writtenPhase = true;
                 }
-                case ANGLE_MODIFIER -> throw new IllegalArgumentException(
-                        "Sun angle pages require a custom sky renderer and are not supported yet");
+                case ANGLE_MODIFIER -> { } // Consumed by the next independently rendered celestial.
                 default -> { }
             }
         }
@@ -71,6 +87,8 @@ public final class AgeEnvironmentCompiler {
     /** Vanilla effects are the sky styles the current renderer can honor exactly. */
     public static ResourceLocation skyEffects(AgeGenerationPlan plan, ResourceLocation fallback) {
         if (plan == null) return fallback;
+        if (skyColor(plan) != -1 || staticSky(plan) || AgeSkyProfile.hasCustomCelestials(plan))
+            return CUSTOM_SKY_EFFECTS;
         return plan.activeSymbols().stream()
                 .filter(symbol -> symbol.semantics().role() == SymbolSemantics.Role.SKY)
                 .map(symbol -> ((SymbolSemantics.ChoiceValue) symbol.semantics().value()).id())
@@ -82,6 +100,52 @@ public final class AgeEnvironmentCompiler {
                 }).findFirst().orElse(fallback);
     }
 
+    public static boolean staticSky(AgeGenerationPlan plan) {
+        return plan != null && plan.activeSymbols().stream().anyMatch(symbol ->
+                symbol.semantics().role() == SymbolSemantics.Role.SKY
+                        && ((SymbolSemantics.ChoiceValue) symbol.semantics().value()).id().equals("static"));
+    }
+
+    /** An authored color is fixed; -1 means the biome or selected vanilla sky supplies it. */
+    public static int skyColor(AgeGenerationPlan plan) {
+        if (plan == null) return -1;
+        return AgeSkyProfile.mixColors(plan.activeSymbols().stream()
+                .filter(symbol -> symbol.semantics().role() == SymbolSemantics.Role.SKY_COLOR)
+                .map(symbol -> ((SymbolSemantics.ChoiceValue) symbol.semantics().value()).id())
+                .map(AgeSkyProfile::color).toList());
+    }
+
+    public static int selectedSkyColor(AgeGenerationPlan plan, ResourceLocation fallback, int biomeSkyColor) {
+        int authored = skyColor(plan);
+        if (authored != -1) return authored;
+        if (staticSky(plan)) return 0xFF929292;
+        ResourceLocation effects = skyEffects(plan, fallback);
+        return previewSkyColor(effects, biomeSkyColor);
+    }
+
+    /** Shared server answer for book previews and the fallback crystal portal surface. */
+    public static int previewSkyColor(ServerLevel level, BlockPos origin) {
+        int biomeColor = level.getBiome(origin).value().getSkyColor();
+        var age = AgeRegistrySavedData.get(level).definitions().stream()
+                .filter(candidate -> AgeDimensionService.dimensionKey(candidate).equals(level.dimension()))
+                .findFirst();
+        if (age.isEmpty()) return previewSkyColor(level.dimensionType().effectsLocation(), biomeColor);
+        var definition = age.orElseThrow();
+        AgeSkyProfile sky = AgeSkyProfile.forAge(definition);
+        if (definition.plan() == null && definition.generationVersion() >= AgeSkyProfile.RANDOM_SKY_GENERATION_VERSION) {
+            if (sky.color() != -1) return sky.color();
+            if (sky.style() == AgeSkyProfile.Style.STATIC) return 0xFF929292;
+        }
+        var profile = definition.plan() == null
+                ? AgeRuntimeProfiles.resolve(definition.generationProfile())
+                : definition.plan().runtimeProfile();
+        ResourceLocation baseEffects = level.getServer().registryAccess()
+                .lookupOrThrow(Registries.DIMENSION_TYPE)
+                .getOrThrow(ResourceKey.create(Registries.DIMENSION_TYPE, profile.dimensionType()))
+                .value().effectsLocation();
+        return selectedSkyColor(definition.plan(), baseEffects, biomeColor);
+    }
+
     public static boolean hasWrittenPhase(AgeGenerationPlan plan) {
         if (plan == null) return false;
         if (plan.version() >= 4) return orderedCelestial(plan, null).writtenPhase();

src/main/java/net/dnorberg/rivencraft/book/AgeGenerationPlan.java

@@ -188,7 +188,7 @@ public record AgeGenerationPlan(int version, long ageSeed, OrderedWriting writin
             String raw = item.getString("Value");
             SymbolSemantics.Value value = switch (role) {
                 case TERRAIN, BIOME, BLOCK, FEATURE -> new SymbolSemantics.ResourceValue(ResourceLocation.parse(raw));
-                case PERIOD_MODIFIER, ANGLE_MODIFIER, PHASE_MODIFIER ->
+                case PERIOD_MODIFIER, ANGLE_MODIFIER, PHASE_MODIFIER, SIZE_MODIFIER ->
                         new SymbolSemantics.NumberValue(Double.parseDouble(raw));
                 default -> new SymbolSemantics.ChoiceValue(raw);
             };

src/main/java/net/dnorberg/rivencraft/book/AgeInstability.java

@@ -15,6 +15,7 @@ import net.minecraft.resources.ResourceLocation;
 public record AgeInstability(int version, int score, List<Contribution> breakdown) {
     public static final int CURRENT_VERSION = 2;
     private static final int BRIGHT_LIGHTING_COST = 500;
+    private static final int INEFFECTIVE_CAVE_PAGE_COST = 100;
     private static final int EXCESS_LEGACY_STRUCTURE_COST = 100;
     private static final int FORCED_STRUCTURE_BIOME_COST = 100;
     private static final Map<ResourceLocation, String> COUNTED_STRUCTURES = Map.ofEntries(
@@ -50,6 +51,10 @@ public record AgeInstability(int version, int score, List<Contribution> breakdow
     }
 
     static AgeInstability compute(AgeGenerationPlan plan, AgeTraits traits, RegistryAccess registries) {
+        return compute(plan, traits, registries, Long.MIN_VALUE);
+    }
+
+    static AgeInstability compute(AgeGenerationPlan plan, AgeTraits traits, RegistryAccess registries, long ageSeed) {
         Objects.requireNonNull(traits, "traits");
         List<Contribution> contributions = new ArrayList<>();
         if (plan == null) {
@@ -81,6 +86,17 @@ public record AgeInstability(int version, int score, List<Contribution> breakdow
             contributions.add(new Contribution("bright_lighting", -1, BRIGHT_LIGHTING_COST,
                     "Seeded bright lighting"));
         }
+        AgeSkyProfile sky = plan == null && ageSeed != Long.MIN_VALUE ? AgeSkyProfile.random(ageSeed, traits)
+                : plan == null ? new AgeSkyProfile(AgeSkyProfile.Style.INHERITED, -1, List.of())
+                : AgeSkyProfile.compile(plan, traits);
+        int seenSuns = 0;
+        for (AgeSkyProfile.Body body : sky.bodies()) {
+            if (body.kind() != AgeSkyProfile.Kind.SUN) continue;
+            if (++seenSuns <= 2) continue;
+            int points = 1000 * (seenSuns - 2);
+            contributions.add(new Contribution("extra_sun", -1, points,
+                    "Sun " + seenSuns + " adds growing instability"));
+        }
         return new AgeInstability(CURRENT_VERSION,
                 contributions.stream().mapToInt(Contribution::points).sum(), contributions);
     }
@@ -88,7 +104,20 @@ public record AgeInstability(int version, int score, List<Contribution> breakdow
     private static void addAuditedSymbolCosts(AgeGenerationPlan plan, RegistryAccess registries,
                                               List<Contribution> contributions) {
         Map<ResourceLocation, Integer> structureCounts = new HashMap<>();
+        boolean cave = AgeBiomeSelection.isCave(plan.runtimeProfile());
         for (AgeGenerationPlan.ResolvedSymbol symbol : plan.symbols()) {
+            if (cave) {
+                var role = symbol.semantics().role();
+                if (switch (role) {
+                    case WEATHER, SEASON, CELESTIAL, PERIOD_MODIFIER, PHASE_MODIFIER,
+                            ANGLE_MODIFIER, DIRECTION_MODIFIER -> true;
+                    default -> false;
+                }) {
+                    contributions.add(new Contribution("cave_ignored_" + role.id(), symbol.index(),
+                            INEFFECTIVE_CAVE_PAGE_COST,
+                            "Sky or weather page has no effect in Cave terrain"));
+                }
+            }
             if (symbol.semantics().role()
                     == net.dnorberg.rivencraft.writing.SymbolSemantics.Role.ENVIRONMENT
                     && symbol.semantics().value()

src/main/java/net/dnorberg/rivencraft/book/AgePersistenceGameTests.java

@@ -23,6 +23,49 @@ public final class AgePersistenceGameTests {
     private AgePersistenceGameTests() {
     }
 
+    @GameTest(template = "empty")
+    public static void modifierSeedChangePersistsWithoutChangingAgeIdentity(GameTestHelper helper) {
+        UUID id = UUID.randomUUID();
+        AgeDefinition original = AgeRegistrySavedData.resolveOrCreate(helper.getLevel(),
+                new AgeReference(id, "Reseed " + id));
+        AgeRegistrySavedData registry = AgeRegistrySavedData.get(helper.getLevel());
+        long newSeed = original.seed() == 987654321L ? 987654322L : 987654321L;
+        helper.assertTrue(registry.reseed(helper.getLevel().getServer(), id, newSeed),
+                "An unoccupied Age must accept a new seed");
+        AgeDefinition changed = registry.find(id).orElseThrow();
+        helper.assertValueEqual(changed.id(), original.id(), "Reseeding must preserve the Age identity");
+        helper.assertValueEqual(changed.dimensionId(), original.dimensionId(),
+                "Reseeding must preserve its dimension and existing chunk location");
+        helper.assertValueEqual(changed.seed(), newSeed, "The new generator seed must be saved");
+        AgeDefinition restored = AgeRegistrySavedData.load(
+                registry.save(new CompoundTag(), helper.getLevel().registryAccess()),
+                helper.getLevel().registryAccess()).find(id).orElseThrow();
+        helper.assertValueEqual(restored.seed(), newSeed, "The new seed must survive reload");
+        var ageLevel = AgeDimensionService.ensureLoaded(helper.getLevel().getServer(), changed);
+        helper.assertTrue(ageLevel != null, "The reseeded Age must reload");
+        helper.assertValueEqual(ageLevel.getSeed(), newSeed,
+                "The runtime level must use the saved seed for new chunks");
+        helper.succeed();
+    }
+
+    @GameTest(template = "empty")
+    public static void retiredAgeIdentitySurvivesSaveAndCannotLoad(GameTestHelper helper) {
+        UUID id = UUID.randomUUID();
+        AgeReference reference = new AgeReference(id, "Retired " + id);
+        AgeDefinition age = AgeRegistrySavedData.resolveOrCreate(helper.getLevel(), reference);
+        AgeRegistrySavedData registry = AgeRegistrySavedData.get(helper.getLevel());
+        helper.assertTrue(registry.markDead(id), "The first retirement must set the tombstone");
+        helper.assertTrue(!registry.markDead(id), "Retirement must be idempotent");
+        helper.assertTrue(AgeDimensionService.ensureLoaded(helper.getLevel().getServer(), age) == null,
+                "A retired Age must never load from an old book");
+        AgeRegistrySavedData restored = AgeRegistrySavedData.load(
+                registry.save(new CompoundTag(), helper.getLevel().registryAccess()),
+                helper.getLevel().registryAccess());
+        helper.assertTrue(restored.isDead(id) && restored.find(id).isPresent(),
+                "Both the retired flag and reserved Age identity must survive reload");
+        helper.succeed();
+    }
+
     @GameTest(template = "empty")
     public static void authoredPlanRetainsResolvedMeaningAndAgeIdentity(GameTestHelper helper) {
         OrderedWriting writing = new OrderedWriting(List.of(

src/main/java/net/dnorberg/rivencraft/book/AgeRegistrySavedData.java

@@ -5,6 +5,9 @@ import java.util.Map;
 import java.util.Optional;
 import java.util.UUID;
 import java.util.List;
+import java.util.HashSet;
+import java.util.Set;
+import net.minecraft.nbt.StringTag;
 import net.dnorberg.rivencraft.writing.OrderedWriting;
 import net.minecraft.core.BlockPos;
 import net.minecraft.core.HolderLookup;
@@ -13,6 +16,7 @@ import net.minecraft.nbt.CompoundTag;
 import net.minecraft.nbt.ListTag;
 import net.minecraft.resources.ResourceLocation;
 import net.minecraft.server.level.ServerLevel;
+import net.minecraft.server.MinecraftServer;
 import net.minecraft.util.datafix.DataFixTypes;
 import net.minecraft.world.level.saveddata.SavedData;
 import net.neoforged.fml.ModList;
@@ -21,6 +25,7 @@ import net.neoforged.fml.ModList;
 public final class AgeRegistrySavedData extends SavedData {
     private static final String DATA_NAME = "rivencraft_ages";
     private static final String AGES_TAG = "Ages";
+    private static final String DEAD_AGES_TAG = "DeadAges";
     private static final String ID_TAG = "Id";
     private static final String NAME_TAG = "Name";
     private static final String SEED_TAG = "Seed";
@@ -50,6 +55,7 @@ public final class AgeRegistrySavedData extends SavedData {
     );
 
     private final Map<UUID, AgeDefinition> ages = new HashMap<>();
+    private final Set<UUID> deadAges = new HashSet<>();
 
     public static AgeRegistrySavedData get(ServerLevel level) {
         return level.getServer().overworld().getDataStorage().computeIfAbsent(FACTORY, DATA_NAME);
@@ -110,6 +116,16 @@ public final class AgeRegistrySavedData extends SavedData {
         return List.copyOf(ages.values());
     }
 
+    public boolean isDead(UUID ageId) { return deadAges.contains(ageId); }
+
+    /** Keep the ID and definition reserved so an old book cannot regenerate a retired Age. */
+    public boolean markDead(UUID ageId) {
+        if (!ages.containsKey(ageId)) return false;
+        boolean changed = deadAges.add(ageId);
+        if (changed) setDirty();
+        return changed;
+    }
+
     public AgeDefinition setSpawn(UUID ageId, BlockPos spawn) {
         AgeDefinition existing = ages.get(ageId);
         if (existing == null) {
@@ -121,6 +137,32 @@ public final class AgeRegistrySavedData extends SavedData {
         return updated;
     }
 
+    /** Changes the generator for future chunks; existing chunk data is deliberately preserved. */
+    public boolean reseed(MinecraftServer server, UUID ageId, long seed) {
+        AgeDefinition previous = ages.get(ageId);
+        if (previous == null || isDead(ageId)) return false;
+        if (previous.seed() == seed) return true;
+        ServerLevel loaded = server.getLevel(AgeDimensionService.dimensionKey(previous));
+        if (loaded != null && !loaded.players().isEmpty()) return false;
+
+        // Legacy changes the Age's seed, not its already-written pages or selected traits.
+        // Keeping the frozen plan and feature list prevents a visited Age from changing
+        // its identity while newly generated chunks use the revised terrain noise.
+        AgeGenerationPlan oldPlan = previous.plan();
+        AgeGenerationPlan plan = oldPlan == null ? null : new AgeGenerationPlan(oldPlan.version(), seed,
+                oldPlan.writing(), oldPlan.symbols(), oldPlan.runtimeProfile(), oldPlan.biomeSelection(),
+                oldPlan.activeSymbolIndices(), oldPlan.writingInstability());
+        AgeDefinition changed = new AgeDefinition(previous.id(), previous.name(), seed,
+                previous.generationProfile(), previous.generationVersion(), previous.createdGameTime(),
+                previous.dimensionId(), previous.spawn(), previous.traits(), plan, previous.seasonMode(),
+                previous.randomFeatures(), previous.instability(), previous.instabilityPlan());
+        if (AgeDimensionService.unload(server, previous) == AgeDimensionService.UnloadResult.FAILED)
+            return false;
+        ages.put(ageId, changed);
+        setDirty();
+        return true;
+    }
+
     private AgeDefinition getOrCreate(AgeReference reference, OrderedWriting writing,
                                       long worldSeed, long createdGameTime, RegistryAccess registries) {
         AgeDefinition existing = ages.get(reference.id());
@@ -134,8 +176,10 @@ public final class AgeRegistrySavedData extends SavedData {
         ResourceLocation seedProfile = AgeRuntimeProfiles.selectForWriting(seed, writing, registries);
         AgeTraits traits = AgeTraits.select(seed);
         AgeGenerationPlan plan = AgeGenerationPlan.compile(writing, seed, seedProfile, traits, registries);
-        AgeTraits effectiveTraits = AgeEnvironmentCompiler.apply(plan, traits);
-        AgeInstability instability = AgeInstability.compute(plan, effectiveTraits, registries);
+        AgeTraits effectiveTraits = plan == null
+                ? AgeEnvironmentCompiler.forTerrain(traits, AgeRuntimeProfiles.resolve(seedProfile))
+                : AgeEnvironmentCompiler.apply(plan, traits);
+        AgeInstability instability = AgeInstability.compute(plan, effectiveTraits, registries, seed);
         AgeInstabilityPlan instabilityPlan = AgeInstabilityPlan.select(instability, seed);
         AgeDefinition created = new AgeDefinition(
                 reference.id(),
@@ -148,7 +192,8 @@ public final class AgeRegistrySavedData extends SavedData {
                 null,
                 effectiveTraits,
                 plan,
-                AgeSeasonMode.select(plan, seed, ModList.get().isLoaded("sereneseasons")),
+                AgeSeasonMode.select(plan, seed, ModList.get().isLoaded("sereneseasons"),
+                        plan == null ? AgeRuntimeProfiles.resolve(seedProfile) : plan.runtimeProfile()),
                 plan == null ? AgeFeatureSelection.randomChoices(seed,
                         AgeRuntimeProfiles.resolve(seedProfile), registries) : List.of(),
                 instability,
@@ -161,6 +206,11 @@ public final class AgeRegistrySavedData extends SavedData {
 
     static AgeRegistrySavedData load(CompoundTag tag, HolderLookup.Provider registries) {
         AgeRegistrySavedData data = new AgeRegistrySavedData();
+        ListTag deadTags = tag.getList(DEAD_AGES_TAG, StringTag.TAG_STRING);
+        for (int index = 0; index < deadTags.size(); index++) {
+            try { data.deadAges.add(UUID.fromString(deadTags.getString(index))); }
+            catch (IllegalArgumentException ignored) { }
+        }
         ListTag serializedAges = tag.getList(AGES_TAG, CompoundTag.TAG_COMPOUND);
         for (int index = 0; index < serializedAges.size(); index++) {
             CompoundTag entry = serializedAges.getCompound(index);
@@ -264,6 +314,9 @@ public final class AgeRegistrySavedData extends SavedData {
                     serializedAges.add(entry);
                 });
         tag.put(AGES_TAG, serializedAges);
+        ListTag deadTags = new ListTag();
+        deadAges.stream().sorted().forEach(id -> deadTags.add(StringTag.valueOf(id.toString())));
+        tag.put(DEAD_AGES_TAG, deadTags);
         return tag;
     }
 

src/main/java/net/dnorberg/rivencraft/book/AgeSeasonMode.java

@@ -19,6 +19,12 @@ public enum AgeSeasonMode {
 
     /** An omitted page is selected once when an Age is created with Serene installed. */
     public static AgeSeasonMode select(AgeGenerationPlan plan, long ageSeed, boolean sereneInstalled) {
+        return select(plan, ageSeed, sereneInstalled, plan == null ? null : plan.runtimeProfile());
+    }
+
+    public static AgeSeasonMode select(AgeGenerationPlan plan, long ageSeed, boolean sereneInstalled,
+                                       AgeRuntimeProfile profile) {
+        if (profile != null && AgeBiomeSelection.isCave(profile)) return NO_SEASONS;
         if (hasAuthoredPage(plan)) return from(plan);
         return sereneInstalled ? LegacyRankChoice.choose(new Random(ageSeed ^ RANDOM_SALT), List.of(
                 new LegacyRankChoice.Option<>(SEASONS, 1),
@@ -31,6 +37,7 @@ public enum AgeSeasonMode {
 
     /** Existing Ages without a stored choice retain their old cycling behavior. */
     public static AgeSeasonMode from(AgeDefinition age) {
+        if (age.caveTerrain()) return NO_SEASONS;
         return age.seasonMode() == null ? from(age.plan()) : age.seasonMode();
     }
 
@@ -49,6 +56,7 @@ public enum AgeSeasonMode {
 
     public static AgeSeasonMode from(AgeGenerationPlan plan) {
         if (plan == null) return SEASONS;
+        if (AgeBiomeSelection.isCave(plan.runtimeProfile())) return NO_SEASONS;
         return plan.activeSymbols().stream()
                 .filter(symbol -> symbol.semantics().role() == SymbolSemantics.Role.SEASON)
                 .map(symbol -> valueOf(((SymbolSemantics.ChoiceValue) symbol.semantics().value())
@@ -58,6 +66,7 @@ public enum AgeSeasonMode {
 
     public static void validate(AgeGenerationPlan plan) {
         if (plan == null) return;
+        if (AgeBiomeSelection.isCave(plan.runtimeProfile())) return;
         if (hasAuthoredPage(plan) && from(plan) != NO_SEASONS
                 && !ModList.get().isLoaded("sereneseasons")) {
             throw new IllegalArgumentException("This seasonal page requires Serene Seasons to create the Age");

src/main/java/net/dnorberg/rivencraft/book/AgeSkyProfile.java

@@ -0,0 +1,181 @@
+package net.dnorberg.rivencraft.book;
+
+import java.util.ArrayList;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Random;
+import java.util.Set;
+import net.dnorberg.rivencraft.writing.SymbolSemantics;
+
+/** The ordered, deterministic sky specification for an Age. No client data is trusted here. */
+public record AgeSkyProfile(Style style, int color, List<Body> bodies) {
+    public static final int RANDOM_SKY_GENERATION_VERSION = 17;
+    private static final int[] COLORS = {0xB74A50, 0xD9834B, 0xDBC574, 0x5AAB80,
+            0x6FA8DF, 0x9870B9, 0xD5DBE1, 0x252531};
+
+    public AgeSkyProfile {
+        bodies = List.copyOf(bodies);
+        long suns = bodies.stream().filter(body -> body.kind() == Kind.SUN).count();
+        long moons = bodies.size() - suns;
+        if (suns > 10 || moons > 10) throw new IllegalArgumentException("An Age may have at most ten suns and ten moons");
+    }
+
+    public static AgeSkyProfile forAge(AgeDefinition age) {
+        if (age.plan() != null) return compile(age.plan(), age.traits());
+        if (age.generationVersion() >= RANDOM_SKY_GENERATION_VERSION)
+            return random(age.seed(), age.traits());
+        return new AgeSkyProfile(Style.INHERITED, -1, List.of());
+    }
+
+    public static AgeSkyProfile random(long seed, AgeTraits traits) {
+        Random random = new Random(seed ^ 0x534B5950524F464CL);
+        Style style = Style.values()[random.nextInt(Style.values().length)];
+        int color = randomColor(random);
+        int suns = random.nextInt(4);
+        int moons = random.nextInt(4);
+        List<Body> bodies = new ArrayList<>();
+        for (int i = 0; i < suns; i++)
+            bodies.add(new Body(Kind.SUN, randomColor(random),
+                    0.75F + random.nextFloat(), random.nextFloat() * 360.0F,
+                    traits.celestialPeriod(), random.nextFloat(), random.nextBoolean()));
+        for (int i = 0; i < moons; i++)
+            bodies.add(new Body(Kind.MOON, randomColor(random),
+                    0.75F + random.nextFloat(), random.nextFloat() * 360.0F,
+                    traits.celestialPeriod(), random.nextFloat(), random.nextBoolean()));
+        return new AgeSkyProfile(style, color, bodies);
+    }
+
+    public static AgeSkyProfile compile(AgeGenerationPlan plan, AgeTraits traits) {
+        if (plan == null) return new AgeSkyProfile(Style.INHERITED, -1, List.of());
+        Style style = Style.INHERITED;
+        int color = AgeEnvironmentCompiler.skyColor(plan);
+        boolean customBodies = hasCustomCelestials(plan);
+        List<Body> bodies = new ArrayList<>();
+        Set<Integer> active = new HashSet<>(plan.activeSymbolIndices());
+        AgeTraits seeded = AgeTraits.select(plan.ageSeed());
+        double period = 1.0D;
+        float angle = seeded.celestialAngle();
+        float phase = seeded.celestialPhase();
+        float size = 1.0F;
+        List<Integer> bodyColors = new ArrayList<>();
+        boolean clockwise = true;
+        for (AgeGenerationPlan.ResolvedSymbol symbol : plan.symbols()) {
+            if (!active.contains(symbol.index())) continue;
+            SymbolSemantics semantics = symbol.semantics();
+            switch (semantics.role()) {
+                case SKY -> style = switch (((SymbolSemantics.ChoiceValue) semantics.value()).id()) {
+                    case "overworld" -> Style.OVERWORLD;
+                    case "nether" -> Style.NETHER;
+                    case "end" -> Style.END;
+                    case "static" -> Style.STATIC;
+                    default -> throw new IllegalArgumentException("Unknown sky style");
+                };
+                case PERIOD_MODIFIER -> period = ((SymbolSemantics.NumberValue) semantics.value()).amount();
+                case ANGLE_MODIFIER -> angle = (float) ((SymbolSemantics.NumberValue) semantics.value()).amount();
+                case PHASE_MODIFIER -> phase = (float) (((SymbolSemantics.NumberValue) semantics.value()).amount() / 360.0D);
+                case SIZE_MODIFIER -> size = (float) ((SymbolSemantics.NumberValue) semantics.value()).amount();
+                case CELESTIAL_COLOR -> bodyColors.add(color(
+                        ((SymbolSemantics.ChoiceValue) semantics.value()).id()));
+                case DIRECTION_MODIFIER -> clockwise = ((SymbolSemantics.ChoiceValue) semantics.value())
+                        .id().equals("clockwise");
+                case CELESTIAL -> {
+                    String choice = ((SymbolSemantics.ChoiceValue) semantics.value()).id();
+                    int bodyColor = bodyColors.isEmpty() ? 0xFFFFFF : mixColors(bodyColors);
+                    if (choice.equals("normal_time")) {
+                        if (customBodies) {
+                            bodies.add(new Body(Kind.SUN, bodyColor, size, angle, period, phase, clockwise));
+                            bodies.add(new Body(Kind.MOON, bodyColor, 1.0F, angle, period,
+                                    (phase + 0.5F) % 1.0F, clockwise));
+                        }
+                    } else {
+                        bodies.add(new Body(choice.equals("sun") ? Kind.SUN : Kind.MOON,
+                                bodyColor, size, angle, period, phase, clockwise));
+                    }
+                    period = 1.0D;
+                    angle = seeded.celestialAngle();
+                    phase = seeded.celestialPhase();
+                    size = 1.0F;
+                    bodyColors.clear();
+                    clockwise = true;
+                }
+                default -> { }
+            }
+        }
+        // Missing branches are seed-completed, including the celestial branch.
+        // An explicit sky or sky-color page does not suppress that completion.
+        if (plan.activeSymbols().stream().noneMatch(symbol ->
+                symbol.semantics().role() == SymbolSemantics.Role.CELESTIAL)) {
+            bodies.addAll(random(plan.ageSeed(), seeded).bodies());
+        }
+        return new AgeSkyProfile(style, color, bodies);
+    }
+
+    public static int mixColors(List<Integer> colors) {
+        if (colors.isEmpty()) return -1;
+        long red = 0, green = 0, blue = 0;
+        for (int color : colors) {
+            red += color >> 16 & 255;
+            green += color >> 8 & 255;
+            blue += color & 255;
+        }
+        int count = colors.size();
+        return (int) ((red + count / 2) / count) << 16
+                | (int) ((green + count / 2) / count) << 8
+                | (int) ((blue + count / 2) / count);
+    }
+
+    private static int randomColor(Random random) {
+        int count = 1 + random.nextInt(3);
+        List<Integer> colors = new ArrayList<>(count);
+        for (int i = 0; i < count; i++) colors.add(COLORS[random.nextInt(COLORS.length)]);
+        return mixColors(colors);
+    }
+
+    public static boolean hasCustomCelestials(AgeGenerationPlan plan) {
+        return plan != null && plan.activeSymbols().stream().anyMatch(symbol ->
+                symbol.semantics().role() == SymbolSemantics.Role.CELESTIAL
+                        && !((SymbolSemantics.ChoiceValue) symbol.semantics().value()).id().equals("normal_time")
+                        || symbol.semantics().role() == SymbolSemantics.Role.CELESTIAL_COLOR
+                        || symbol.semantics().role() == SymbolSemantics.Role.SIZE_MODIFIER
+                        || symbol.semantics().role() == SymbolSemantics.Role.DIRECTION_MODIFIER);
+    }
+
+    public boolean custom() {
+        return style == Style.STATIC || color != -1 || !bodies.isEmpty();
+    }
+
+    /** Vanilla has one skylight channel; combine visible bodies into that channel. */
+    public float lightAt(double dayTime) {
+        float sunlight = 0.0F;
+        float moonlight = 0.0F;
+        for (Body body : bodies) {
+            double orbit = body.period() == 0.0D ? body.phase()
+                    : (body.clockwise() ? 1.0D : -1.0D) * dayTime
+                            / (24000.0D * body.period()) + body.phase();
+            float altitude = (float) Math.cos(orbit * Math.PI * 2.0D);
+            if (altitude <= 0.0F) continue;
+            if (body.kind() == Kind.SUN) sunlight += altitude;
+            else moonlight += altitude * 0.18F;
+        }
+        return Math.min(1.0F, sunlight > 0.0F ? sunlight : moonlight);
+    }
+
+    public static int color(String name) {
+        return switch (name) {
+            case "red" -> COLORS[0];
+            case "orange" -> COLORS[1];
+            case "yellow" -> COLORS[2];
+            case "green" -> COLORS[3];
+            case "blue" -> COLORS[4];
+            case "purple" -> COLORS[5];
+            case "white" -> COLORS[6];
+            case "black" -> COLORS[7];
+            default -> throw new IllegalArgumentException("Unknown sky color " + name);
+        };
+    }
+
+    public enum Style { INHERITED, OVERWORLD, NETHER, END, STATIC }
+    public enum Kind { SUN, MOON }
+    public record Body(Kind kind, int color, float size, float angle,
+                       double period, float phase, boolean clockwise) { }
+}

src/main/java/net/dnorberg/rivencraft/book/AgeWeatherService.java

@@ -26,7 +26,7 @@ public final class AgeWeatherService {
             return;
         }
 
-        AgeTraits.Weather weather = age.traits().weather();
+        AgeTraits.Weather weather = age.caveTerrain() ? AgeTraits.Weather.OFF : age.traits().weather();
         if (weather == AgeTraits.Weather.NORMAL) {
             STATES.remove(level);
             return;

src/main/java/net/dnorberg/rivencraft/book/CaveTerrainGameTests.java

@@ -0,0 +1,90 @@
+package net.dnorberg.rivencraft.book;
+
+import java.util.List;
+import java.util.UUID;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.writing.OrderedWriting;
+import net.dnorberg.rivencraft.writing.SymbolReference;
+import net.dnorberg.rivencraft.writing.WritingEntry;
+import net.minecraft.gametest.framework.GameTest;
+import net.minecraft.gametest.framework.GameTestHelper;
+import net.minecraft.nbt.CompoundTag;
+import net.minecraft.resources.ResourceLocation;
+import net.minecraft.world.level.biome.Biomes;
+import net.neoforged.neoforge.gametest.GameTestHolder;
+import net.neoforged.neoforge.gametest.PrefixGameTestTemplate;
+
+/** Focused Cave terrain writing and persisted-generation coverage for issue #14. */
+@GameTestHolder(Rivencraft.MOD_ID)
+@PrefixGameTestTemplate(false)
+public final class CaveTerrainGameTests {
+    private CaveTerrainGameTests() {}
+
+    @GameTest(template = "empty")
+    public static void caveSkyAndWeatherPagesCostInstabilityButDoNotApply(GameTestHelper helper) {
+        OrderedWriting cave = writing("terrain/cave", "biome/lush_caves", "biome/nether_wastes",
+                "biome/tiled", "weather/storm", "season/eternal_winter", "period/zero",
+                "celestial/normal_time");
+        AgeTraits seeded = new AgeTraits(AgeTraits.BiomeDistribution.SINGLE, AgeTraits.Lighting.NORMAL,
+                AgeTraits.Weather.ALWAYS, 0.5D, 0.0F, 0.25F);
+        var registries = helper.getLevel().registryAccess();
+        AgeGenerationPlan plan = AgeGenerationPlan.compile(cave, 42L, AgeGenerationProfiles.CAVE,
+                seeded, registries);
+        AgeTraits applied = AgeEnvironmentCompiler.apply(plan, seeded);
+        helper.assertValueEqual(applied.weather(), AgeTraits.Weather.OFF, "Cave weather must be off");
+        helper.assertValueEqual(applied.celestialPeriod(), 1.0D, "Cave time pages must not alter the clock");
+        helper.assertValueEqual(applied.celestialPhase(), 0.0F, "Cave time pages must not set a phase");
+        helper.assertValueEqual(AgeSeasonMode.select(plan, 42L, true), AgeSeasonMode.NO_SEASONS,
+                "Cave seasons must be disabled even when Serene Seasons is present");
+        helper.assertValueEqual(plan.biomeSelection().biomes(),
+                List.of(Biomes.LUSH_CAVES.location(), Biomes.NETHER_WASTES.location()),
+                "Cave writing must retain exactly its cave and Nether biomes");
+        AgeInstability instability = AgeInstability.compute(plan, applied, registries);
+        helper.assertValueEqual(instability.breakdown().stream()
+                        .filter(part -> part.reason().startsWith("cave_ignored_")).count(), 4L,
+                "Each ineffective weather, season, period, and celestial page must add instability");
+        helper.assertValueEqual(AgeInstability.compute(AgeGenerationPlan.load(plan.save()), applied, registries),
+                instability, "Cave page penalties must survive plan reload");
+
+        AgeGenerationPlan surfaceCaves = AgeGenerationPlan.compile(writing("terrain/standard", "feature/caves"),
+                42L, AgeGenerationProfiles.STANDARD, seeded, registries);
+        helper.assertTrue(!AgeBiomeSelection.isCave(surfaceCaves.runtimeProfile())
+                        && AgeFeatureSelection.resolved(surfaceCaves).stream()
+                        .anyMatch(choice -> AgeFeatureSelection.caves(choice.id())),
+                "The separate Caves feature page must still add caves to surface terrain");
+        helper.succeed();
+    }
+
+    @GameTest(template = "empty", timeoutTicks = 600)
+    public static void authoredCaveBiomeAndSpawnSurviveSavedDataReload(GameTestHelper helper) {
+        var player = helper.makeMockServerPlayerInLevel();
+        AgeReference reference = new AgeReference(UUID.randomUUID(), "Cave issue 14 " + UUID.randomUUID());
+        AgeDimensionService.resolve(player, reference,
+                writing("terrain/cave", "biome/nether_wastes", "biome/single")).orElseThrow();
+        var registry = AgeRegistrySavedData.get(helper.getLevel());
+        AgeDefinition age = registry.find(reference.id()).orElseThrow();
+        helper.assertTrue(age.caveTerrain(), "The Age must retain Cave terrain");
+        helper.assertTrue(age.spawn() != null && age.spawn().getY() <= 64,
+                "Cave spawn search must start at Y=64, not atop the roof");
+        helper.assertValueEqual(age.traits().weather(), AgeTraits.Weather.OFF,
+                "A new Cave Age must persist disabled weather");
+        helper.assertValueEqual(age.seasonMode(), AgeSeasonMode.NO_SEASONS,
+                "A new Cave Age must persist disabled seasons");
+        AgeDefinition reloaded = AgeRegistrySavedData.load(
+                registry.save(new CompoundTag(), helper.getLevel().registryAccess()),
+                helper.getLevel().registryAccess()).find(reference.id()).orElseThrow();
+        helper.assertValueEqual(reloaded, age, "Saved Cave biome, spawn, and environment must survive reload");
+        helper.assertValueEqual(reloaded.plan().biomeSelection().biomes(),
+                List.of(Biomes.NETHER_WASTES.location()),
+                "The generated Cave Age must preserve its authored-only Nether pool");
+        helper.succeed();
+    }
+
+    private static OrderedWriting writing(String... pages) {
+        var entries = new java.util.ArrayList<WritingEntry>();
+        entries.add(WritingEntry.linkPanel());
+        for (String page : pages) entries.add(WritingEntry.symbol(new SymbolReference(
+                ResourceLocation.parse("rivencraft:" + page))));
+        return new OrderedWriting(entries);
+    }
+}

src/main/java/net/dnorberg/rivencraft/book/CloudPlatformGameTests.java

@@ -20,6 +20,9 @@ public final class CloudPlatformGameTests {
         helper.getLevel().setBlock(pos, state, 2);
         helper.assertTrue(!state.getCollisionShape(helper.getLevel(), pos).isEmpty(),
                 "Cloud platform must support a standing player");
+        helper.assertTrue(state.canOcclude(), "Arrival platform must be opaque");
+        helper.assertValueEqual(state.getDestroySpeed(helper.getLevel(), pos), 0.3F,
+                "Arrival platform should break as easily as glass");
         helper.assertTrue(ModBlocks.CLOUD_PLATFORM.get().getCloneItemStack(helper.getLevel(), pos, state).isEmpty(),
                 "Cloud platform must not provide a pick-block item");
         helper.succeed();

src/main/java/net/dnorberg/rivencraft/book/EnvironmentWritingGameTests.java

@@ -52,9 +52,11 @@ public final class EnvironmentWritingGameTests {
     public static void environmentPagesEnterCreativeAndJeiFeed(GameTestHelper helper) {
         Set<String> expected = Set.of(
                 "lighting/normal", "lighting/dark", "lighting/bright",
-                "sky/overworld", "sky/nether", "sky/end",
+                "sky/overworld", "sky/nether", "sky/end", "sky/static", "sky_color/purple",
                 "weather/normal", "weather/fast", "weather/slow", "weather/off",
-                "weather/always", "weather/storm", "celestial/normal_time",
+                "weather/always", "weather/storm", "celestial/normal_time", "celestial/sun",
+                "celestial/moon", "celestial_color/red", "size/large", "angle/east",
+                "direction/clockwise", "direction/counterclockwise",
                 "season/no_seasons", "season/seasons", "season/eternal_winter",
                 "season/eternal_summer", "season/eternal_fall", "season/eternal_spring",
                 "period/zero", "period/half", "period/full", "period/double",
@@ -135,6 +137,104 @@ public final class EnvironmentWritingGameTests {
         helper.succeed();
     }
 
+    @GameTest(template = "empty")
+    public static void authoredStaticSkyColorSurvivesWritingAndFeedsPreview(GameTestHelper helper) {
+        OrderedWriting writing = new OrderedWriting(List.of(
+                WritingEntry.linkPanel(), page("terrain/standard"), page("sky/static"),
+                page("sky_color/purple"), page("celestial/normal_time")));
+        AgeTraits seeded = AgeTraits.select(44L);
+        AgeGenerationPlan plan = AgeGenerationPlan.compile(writing, 44L, AgeGenerationProfiles.STANDARD,
+                seeded, helper.getLevel().registryAccess());
+        helper.assertTrue(AgeEnvironmentCompiler.staticSky(plan),
+                "The authored Static Sky page must survive Age compilation");
+        helper.assertValueEqual(AgeEnvironmentCompiler.skyEffects(plan, BuiltinDimensionTypes.OVERWORLD_EFFECTS),
+                AgeEnvironmentCompiler.CUSTOM_SKY_EFFECTS,
+                "The static sky must select Rivencraft's custom renderer");
+        helper.assertValueEqual(AgeEnvironmentCompiler.selectedSkyColor(plan,
+                        BuiltinDimensionTypes.OVERWORLD_EFFECTS, 0xFF77AAFF),
+                0x9870B9, "The authored color must tint the sky and preview consistently");
+        AgeGenerationPlan restored = AgeGenerationPlan.load(plan.save());
+        helper.assertTrue(AgeEnvironmentCompiler.staticSky(restored),
+                "A saved Age must retain its static sky choice");
+        helper.assertValueEqual(AgeEnvironmentCompiler.skyColor(restored), 0x9870B9,
+                "A saved Age must retain its sky color choice");
+        AgeGenerationPlan coloredEnd = AgeGenerationPlan.compile(new OrderedWriting(List.of(
+                        WritingEntry.linkPanel(), page("terrain/standard"), page("sky/end"),
+                        page("sky_color/red"), page("celestial/normal_time"))),
+                45L, AgeGenerationProfiles.STANDARD, AgeTraits.select(45L),
+                helper.getLevel().registryAccess());
+        helper.assertValueEqual(AgeEnvironmentCompiler.skyEffects(coloredEnd,
+                        BuiltinDimensionTypes.OVERWORLD_EFFECTS),
+                AgeEnvironmentCompiler.CUSTOM_SKY_EFFECTS,
+                "A color page must make non-Overworld skies renderable by the custom sky effect");
+        helper.assertValueEqual(AgeEnvironmentCompiler.selectedSkyColor(coloredEnd,
+                        BuiltinDimensionTypes.OVERWORLD_EFFECTS, 0xFF77AAFF),
+                0xB74A50, "A color page must override the selected sky type's default tint");
+        helper.assertTrue(PageItem.bundledCreativeSymbols().contains("sky/static")
+                        && PageItem.bundledCreativeSymbols().contains("sky_color/purple"),
+                "New sky pages must be available through the Creative and JEI page catalog");
+        helper.succeed();
+    }
+
+    @GameTest(template = "empty")
+    public static void skyAndCelestialColorsBlendWithoutRequiringBodies(GameTestHelper helper) {
+        OrderedWriting writing = new OrderedWriting(List.of(
+                WritingEntry.linkPanel(), page("terrain/standard"), page("sky/overworld"),
+                page("sky_color/red"), page("sky_color/blue"),
+                page("celestial_color/yellow"), page("celestial_color/blue"), page("celestial/sun")));
+        helper.assertTrue(WritingGrammar.parse(writing).canCreate(),
+                "Two sky colors and two colors for one sun must be valid writing");
+        AgeTraits traits = AgeTraits.select(46L);
+        AgeGenerationPlan plan = AgeGenerationPlan.compile(writing, 46L,
+                AgeGenerationProfiles.STANDARD, traits, helper.getLevel().registryAccess());
+        int skyColor = AgeSkyProfile.mixColors(List.of(
+                AgeSkyProfile.color("red"), AgeSkyProfile.color("blue")));
+        int sunColor = AgeSkyProfile.mixColors(List.of(
+                AgeSkyProfile.color("yellow"), AgeSkyProfile.color("blue")));
+        helper.assertValueEqual(AgeEnvironmentCompiler.skyColor(plan), skyColor,
+                "Sky color pages must blend without discarding either page");
+        AgeSkyProfile profile = AgeSkyProfile.compile(plan, traits);
+        helper.assertValueEqual(profile.bodies().size(), 1, "The written Age has exactly one sun");
+        helper.assertValueEqual(profile.bodies().getFirst().color(), sunColor,
+                "Celestial colors must blend for the following body");
+        helper.assertValueEqual(AgeSkyProfile.compile(AgeGenerationPlan.load(plan.save()), traits), profile,
+                "Blended colors must survive the saved writing plan");
+
+        AgeSkyProfile bodyless = new AgeSkyProfile(AgeSkyProfile.Style.OVERWORLD, skyColor, List.of());
+        helper.assertTrue(bodyless.custom() && bodyless.bodies().isEmpty(),
+                "An Age can have an authored sky without any celestial bodies");
+        helper.succeed();
+    }
+
+    @GameTest(template = "empty")
+    public static void randomAndAuthoredCelestialsKeepIndependentOrbits(GameTestHelper helper) {
+        AgeTraits traits = AgeTraits.select(12345L);
+        AgeSkyProfile first = AgeSkyProfile.random(12345L, traits);
+        helper.assertValueEqual(first, AgeSkyProfile.random(12345L, traits),
+                "A random Age must recreate the same sky from its saved seed");
+        helper.assertTrue(first.bodies().stream().filter(body -> body.kind() == AgeSkyProfile.Kind.SUN).count() <= 10
+                        && first.bodies().stream().filter(body -> body.kind() == AgeSkyProfile.Kind.MOON).count() <= 10,
+                "Random Ages must obey the same celestial limits as authored Ages");
+        OrderedWriting writing = new OrderedWriting(List.of(
+                WritingEntry.linkPanel(), page("terrain/standard"), page("sky/end"),
+                page("angle/east"), page("direction/counterclockwise"), page("celestial_color/red"),
+                page("size/large"), page("period/half"), page("celestial/sun"),
+                page("direction/clockwise"), page("celestial/moon")));
+        AgeGenerationPlan plan = AgeGenerationPlan.compile(writing, 12345L, AgeGenerationProfiles.STANDARD,
+                traits, helper.getLevel().registryAccess());
+        AgeSkyProfile sky = AgeSkyProfile.compile(plan, AgeEnvironmentCompiler.apply(plan, traits));
+        helper.assertValueEqual(sky.bodies().size(), 2, "Both written celestial bodies must be retained");
+        helper.assertValueEqual(sky.bodies().getFirst().angle(), 90.0F,
+                "The first body's compass angle must be independent");
+        helper.assertFalse(sky.bodies().getFirst().clockwise(),
+                "The first body should move counterclockwise");
+        helper.assertTrue(sky.bodies().getLast().clockwise(),
+                "The second body should move clockwise");
+        helper.assertValueEqual(AgeSkyProfile.compile(AgeGenerationPlan.load(plan.save()), traits), sky,
+                "Body angle and direction must survive Age-plan serialization");
+        helper.succeed();
+    }
+
     @GameTest(template = "empty")
     public static void writtenEnvironmentPersistsAndPageFreeAgesStaySeeded(GameTestHelper helper) {
         OrderedWriting writing = new OrderedWriting(List.of(

src/main/java/net/dnorberg/rivencraft/book/HandheldBookTravelGameTests.java

@@ -0,0 +1,127 @@
+package net.dnorberg.rivencraft.book;
+
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.entity.DroppedBookEntity;
+import net.dnorberg.rivencraft.registry.ModEntities;
+import net.dnorberg.rivencraft.registry.ModItems;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.GlobalPos;
+import net.minecraft.gametest.framework.GameTest;
+import net.minecraft.gametest.framework.GameTestHelper;
+import net.minecraft.nbt.CompoundTag;
+import net.minecraft.world.InteractionHand;
+import net.minecraft.world.entity.item.ItemEntity;
+import net.minecraft.world.item.ItemStack;
+import net.minecraft.world.item.Items;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.phys.AABB;
+import net.neoforged.neoforge.gametest.GameTestHolder;
+import net.neoforged.neoforge.gametest.PrefixGameTestTemplate;
+
+@GameTestHolder(Rivencraft.MOD_ID)
+@PrefixGameTestTemplate(false)
+public final class HandheldBookTravelGameTests {
+    private HandheldBookTravelGameTests() {
+    }
+
+    @GameTest(template = "empty")
+    public static void successfulHandheldTravelLeavesOnlyActiveBookAtOrigin(GameTestHelper helper) {
+        var player = helper.makeMockServerPlayerInLevel();
+        ItemStack book = new ItemStack(ModItems.LINKING_BOOK.get());
+        player.setItemInHand(InteractionHand.MAIN_HAND, book);
+        player.getInventory().setItem(1, new ItemStack(Items.DIAMOND));
+        var source = player.position();
+        BlockPos destination = helper.absolutePos(new BlockPos(2, 1, 2));
+        helper.getLevel().setBlock(destination, Blocks.AIR.defaultBlockState(), 2);
+        helper.getLevel().setBlock(destination.above(), Blocks.AIR.defaultBlockState(), 2);
+        LinkTarget target = new LinkTarget(GlobalPos.of(helper.getLevel().dimension(), destination), 0, 0);
+
+        helper.assertValueEqual(LinkingService.travelHandheld(player, InteractionHand.MAIN_HAND, book, target,
+                        new LinkProperties(LinkProperties.INTRA_LINKING), false), LinkingService.LinkResult.SUCCESS,
+                "A valid intra-dimensional handheld link must succeed");
+        helper.assertTrue(player.getMainHandItem().isEmpty(), "Only the active book must leave the hand");
+        helper.assertTrue(player.getInventory().getItem(1).is(Items.DIAMOND),
+                "An unrelated inventory item must remain with the player");
+        var drops = helper.getLevel().getEntitiesOfClass(DroppedBookEntity.class, new AABB(source, source).inflate(2.0),
+                entity -> entity.getItem().is(ModItems.LINKING_BOOK.get()));
+        helper.assertValueEqual(drops.size(), 1, "Exactly one recoverable book must remain at the departure point");
+        helper.assertTrue(drops.getFirst().getItem() == book,
+                "The model-rendered entity must retain the exact active book stack");
+        helper.assertTrue(drops.getFirst().copy() instanceof DroppedBookEntity,
+                "The pickup-animation copy must keep the custom renderer's entity type");
+        helper.succeed();
+    }
+
+    @GameTest(template = "empty")
+    public static void rejectedHandheldTravelKeepsBook(GameTestHelper helper) {
+        var player = helper.makeMockServerPlayerInLevel();
+        ItemStack book = new ItemStack(ModItems.LINKING_BOOK.get());
+        player.setItemInHand(InteractionHand.OFF_HAND, book);
+        LinkTarget target = new LinkTarget(GlobalPos.of(helper.getLevel().dimension(), player.blockPosition()), 0, 0);
+
+        helper.assertValueEqual(LinkingService.travelHandheld(player, InteractionHand.OFF_HAND, book, target,
+                        LinkProperties.NONE, false), LinkingService.LinkResult.INTRA_LINKING_REQUIRED,
+                "A same-dimension link without Intra Linking must be rejected");
+        helper.assertTrue(player.getOffhandItem() == book, "The exact rejected book must be restored to its hand");
+        helper.assertTrue(helper.getLevel().getEntitiesOfClass(ItemEntity.class,
+                new AABB(player.position(), player.position()).inflate(2.0),
+                entity -> entity.getItem().is(ModItems.LINKING_BOOK.get())).isEmpty(),
+                "A rejected link must not leave a second copy at the origin");
+        helper.succeed();
+    }
+
+    @GameTest(template = "empty")
+    public static void disarmDropsOtherInventoryWithoutDuplicatingActiveBook(GameTestHelper helper) {
+        var player = helper.makeMockServerPlayerInLevel();
+        ItemStack book = new ItemStack(ModItems.LINKING_BOOK.get());
+        player.setItemInHand(InteractionHand.MAIN_HAND, book);
+        player.getInventory().setItem(1, new ItemStack(Items.DIAMOND));
+        var source = player.position();
+        BlockPos destination = helper.absolutePos(new BlockPos(2, 1, 2));
+        helper.getLevel().setBlock(destination, Blocks.AIR.defaultBlockState(), 2);
+        helper.getLevel().setBlock(destination.above(), Blocks.AIR.defaultBlockState(), 2);
+        LinkTarget target = new LinkTarget(GlobalPos.of(helper.getLevel().dimension(), destination), 0, 0);
+
+        helper.assertValueEqual(LinkingService.travelHandheld(player, InteractionHand.MAIN_HAND, book, target,
+                        new LinkProperties(LinkProperties.INTRA_LINKING | LinkProperties.DISARM), false),
+                LinkingService.LinkResult.SUCCESS, "Disarm must not block handheld travel");
+        var drops = helper.getLevel().getEntitiesOfClass(ItemEntity.class, new AABB(source, source).inflate(2.0));
+        helper.assertValueEqual(drops.stream().filter(entity -> entity instanceof DroppedBookEntity).count(),
+                1L, "Disarm must not create a second copy of the active book");
+        helper.assertValueEqual(drops.stream().filter(entity -> entity.getItem().is(Items.DIAMOND)).count(),
+                1L, "Disarm must still drop unrelated inventory items");
+        helper.succeed();
+    }
+
+    @GameTest(template = "empty")
+    public static void originBookUsesSlowDecayWithoutVanillaDespawn(GameTestHelper helper) {
+        DroppedBookEntity book = new DroppedBookEntity(helper.getLevel(),
+                net.minecraft.world.phys.Vec3.ZERO, new ItemStack(ModItems.LINKING_BOOK.get()));
+        CompoundTag seeded = new CompoundTag();
+        book.saveWithoutId(seeded);
+        seeded.putInt("BookDecayTicks", 9_999);
+        book.readAdditionalSaveData(seeded);
+        book.tick();
+        CompoundTag saved = new CompoundTag();
+        book.saveWithoutId(saved);
+        helper.assertValueEqual(saved.getShort("Age"), (short)-32_768,
+                "The dropped book must not expire after vanilla's five minutes");
+        helper.assertValueEqual(saved.getShort("Health"), (short)4,
+                "A dropped book must lose one item-health point after 10,000 loaded ticks");
+        helper.assertValueEqual(saved.getInt("BookDecayTicks"), 0,
+                "Slow decay must reset its interval and persist across a restart");
+        DroppedBookEntity restored = new DroppedBookEntity(ModEntities.DROPPED_BOOK.get(), helper.getLevel());
+        restored.readAdditionalSaveData(saved);
+        CompoundTag resaved = new CompoundTag();
+        restored.saveWithoutId(resaved);
+        helper.assertTrue(restored.getItem().is(ModItems.LINKING_BOOK.get()),
+                "The custom book entity must retain its book on reload");
+        helper.assertValueEqual(resaved.getShort("Age"), (short)-32_768,
+                "The custom book must remain non-despawning after reload");
+        helper.assertValueEqual(resaved.getShort("Health"), (short)4,
+                "Decay damage must persist after reload");
+        helper.assertTrue(restored.copy().getItem().is(ModItems.LINKING_BOOK.get()),
+                "A pickup-animation copy must retain the book data after reload");
+        helper.succeed();
+    }
+}

src/main/java/net/dnorberg/rivencraft/book/LinkDisarmService.java

@@ -0,0 +1,58 @@
+package net.dnorberg.rivencraft.book;
+
+import net.dnorberg.rivencraft.mixin.MobDropChanceAccessor;
+import net.minecraft.world.Container;
+import net.minecraft.world.entity.Entity;
+import net.minecraft.world.entity.EquipmentSlot;
+import net.minecraft.world.entity.Mob;
+import net.minecraft.world.entity.animal.horse.AbstractHorse;
+import net.minecraft.world.entity.item.ItemEntity;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.world.item.ItemStack;
+
+/** Legacy-style Disarm: leave carried items and eligible equipment at the departure point. */
+public final class LinkDisarmService {
+    private LinkDisarmService() {}
+
+    public static boolean mayTravel(Entity entity) {
+        // Legacy refuses loose items and dropped Link Books on Disarm links.
+        return !(entity instanceof ItemEntity);
+    }
+
+    public static void disarm(Entity entity) {
+        if (entity instanceof ServerPlayer player) {
+            eject(player, player.getInventory());
+            player.containerMenu.broadcastChanges();
+        }
+        if (entity instanceof Container container) eject(entity, container);
+        if (entity instanceof AbstractHorse horse) eject(entity, horse.getInventory());
+        if (entity instanceof Mob mob) dropEquipment(mob);
+    }
+
+    private static void eject(Entity carrier, Container inventory) {
+        for (int slot = 0; slot < inventory.getContainerSize(); slot++) {
+            ItemStack stack = inventory.getItem(slot);
+            if (stack.isEmpty()) continue;
+            inventory.setItem(slot, ItemStack.EMPTY);
+            carrier.spawnAtLocation(stack);
+        }
+        inventory.setChanged();
+    }
+
+    private static void dropEquipment(Mob mob) {
+        for (EquipmentSlot slot : EquipmentSlot.values()) {
+            ItemStack stack = mob.getItemBySlot(slot);
+            if (stack.isEmpty()) continue;
+            float chance = ((MobDropChanceAccessor) mob).rivencraft$getEquipmentDropChance(slot);
+            mob.setItemSlot(slot, ItemStack.EMPTY);
+            if (chance <= 0 || mob.getRandom().nextFloat() >= chance) continue;
+            if (chance <= 1 && stack.isDamageableItem()) {
+                int minimum = Math.max(stack.getMaxDamage() - 25, 1);
+                int damage = stack.getMaxDamage() - mob.getRandom().nextInt(
+                        1 + mob.getRandom().nextInt(minimum));
+                stack.setDamageValue(Math.clamp(damage, 1, minimum));
+            }
+            mob.spawnAtLocation(stack);
+        }
+    }
+}

src/main/java/net/dnorberg/rivencraft/book/LinkModifierBehaviorGameTests.java

@@ -0,0 +1,125 @@
+package net.dnorberg.rivencraft.book;
+
+import net.dnorberg.rivencraft.Rivencraft;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.GlobalPos;
+import net.minecraft.gametest.framework.GameTest;
+import net.minecraft.gametest.framework.GameTestHelper;
+import net.minecraft.world.entity.EquipmentSlot;
+import net.minecraft.world.entity.EntityType;
+import net.minecraft.world.entity.animal.horse.Donkey;
+import net.minecraft.world.entity.item.ItemEntity;
+import net.minecraft.world.entity.monster.Zombie;
+import net.minecraft.world.entity.vehicle.MinecartChest;
+import net.minecraft.world.item.ItemStack;
+import net.minecraft.world.item.Items;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.phys.AABB;
+import net.minecraft.world.phys.Vec3;
+import net.neoforged.neoforge.gametest.GameTestHolder;
+import net.neoforged.neoforge.gametest.PrefixGameTestTemplate;
+
+@GameTestHolder(Rivencraft.MOD_ID)
+@PrefixGameTestTemplate(false)
+public final class LinkModifierBehaviorGameTests {
+    private LinkModifierBehaviorGameTests() {}
+
+    @GameTest(template = "empty")
+    public static void maintainMomentumRotatesToDestinationYaw(GameTestHelper helper) {
+        Vec3 result = LinkingService.rotatedMomentum(new Vec3(3, -0.5, 4), 90);
+        helper.assertTrue(Math.abs(result.x) < 0.0001 && Math.abs(result.y + 0.3) < 0.0001
+                        && Math.abs(result.z - 5) < 0.0001,
+                "Legacy momentum preserves horizontal speed, rotates to destination yaw, and adds a small lift");
+        helper.succeed();
+    }
+
+    @GameTest(template = "empty")
+    public static void disarmRefusesLooseItems(GameTestHelper helper) {
+        var level = helper.getLevel();
+        ItemEntity item = new ItemEntity(level, 1, 1, 1, new ItemStack(Items.DIAMOND));
+        level.addFreshEntity(item);
+        LinkTarget target = new LinkTarget(GlobalPos.of(level.dimension(), helper.absolutePos(new BlockPos(2, 1, 2))),
+                0, 0);
+        helper.assertValueEqual(LinkingService.travelEntityPortal(item, target,
+                        new LinkProperties(LinkProperties.DISARM | LinkProperties.INTRA_LINKING), false),
+                LinkingService.LinkResult.DISARM_REJECTED,
+                "Legacy Disarm must refuse a loose item before teleportation");
+        helper.assertTrue(item.isAlive() && item.getItem().is(Items.DIAMOND),
+                "Rejected item must remain at the source");
+        helper.succeed();
+    }
+
+    @GameTest(template = "empty")
+    public static void ordinaryLinkMovesLooseItemWithoutMakingPlatform(GameTestHelper helper) {
+        var level = helper.getLevel();
+        BlockPos landing = helper.absolutePos(new BlockPos(2, 2, 2));
+        level.setBlock(landing.below(), Blocks.AIR.defaultBlockState(), 2);
+        level.setBlock(landing, Blocks.AIR.defaultBlockState(), 2);
+        level.setBlock(landing.above(), Blocks.AIR.defaultBlockState(), 2);
+        ItemEntity item = new ItemEntity(level, 1, 1, 1, new ItemStack(Items.DIAMOND));
+        level.addFreshEntity(item);
+        LinkTarget target = new LinkTarget(GlobalPos.of(level.dimension(), landing), 0, 0);
+        helper.assertValueEqual(LinkingService.travelEntityPortal(item, target,
+                        new LinkProperties(LinkProperties.INTRA_LINKING), false),
+                LinkingService.LinkResult.SUCCESS, "Ordinary portal links may carry loose items");
+        helper.assertTrue(item.blockPosition().distManhattan(landing) <= 1,
+                "Item must arrive at the linked location");
+        helper.assertTrue(level.getBlockState(landing.below()).isAir(),
+                "A Linking Book must not generate a landing platform by default");
+        helper.succeed();
+    }
+
+    @GameTest(template = "empty")
+    public static void explicitGeneratePlatformAddsOnlyArrivalFloor(GameTestHelper helper) {
+        var level = helper.getLevel();
+        BlockPos landing = helper.absolutePos(new BlockPos(2, 2, 2));
+        level.setBlock(landing.below(), Blocks.AIR.defaultBlockState(), 2);
+        level.setBlock(landing, Blocks.AIR.defaultBlockState(), 2);
+        level.setBlock(landing.above(), Blocks.AIR.defaultBlockState(), 2);
+        level.setBlock(landing.above(2), Blocks.AIR.defaultBlockState(), 2);
+        ItemEntity item = new ItemEntity(level, 1, 1, 1, new ItemStack(Items.DIAMOND));
+        level.addFreshEntity(item);
+        LinkTarget target = new LinkTarget(GlobalPos.of(level.dimension(), landing), 0, 0);
+        helper.assertValueEqual(LinkingService.travelEntityPortal(item, target,
+                        new LinkProperties(LinkProperties.INTRA_LINKING | LinkProperties.GENERATE_PLATFORM), false),
+                LinkingService.LinkResult.SUCCESS, "An explicit platform link must travel");
+        helper.assertTrue(level.getBlockState(landing.below()).is(
+                        net.dnorberg.rivencraft.registry.ModBlocks.CLOUD_PLATFORM.get()),
+                "An enabled Linking Book platform must add one cloud block below the arrival");
+        helper.succeed();
+    }
+
+    @GameTest(template = "empty")
+    public static void disarmEmptiesCarrierAndMobEquipment(GameTestHelper helper) {
+        var level = helper.getLevel();
+        Vec3 source = Vec3.atCenterOf(helper.absolutePos(new BlockPos(1, 1, 1)));
+        MinecartChest cart = EntityType.CHEST_MINECART.create(level);
+        Donkey donkey = EntityType.DONKEY.create(level);
+        Zombie zombie = EntityType.ZOMBIE.create(level);
+        helper.assertTrue(cart != null && donkey != null && zombie != null, "Carriers must instantiate");
+        cart.setPos(source);
+        donkey.setPos(source);
+        zombie.setPos(source);
+        level.addFreshEntity(cart);
+        level.addFreshEntity(donkey);
+        level.addFreshEntity(zombie);
+        cart.setItem(0, new ItemStack(Items.EMERALD));
+        donkey.getInventory().setItem(0, new ItemStack(Items.SADDLE));
+        zombie.setItemSlot(EquipmentSlot.MAINHAND, new ItemStack(Items.IRON_SWORD));
+        zombie.setDropChance(EquipmentSlot.MAINHAND, 2.0F);
+
+        LinkDisarmService.disarm(cart);
+        LinkDisarmService.disarm(donkey);
+        LinkDisarmService.disarm(zombie);
+
+        helper.assertTrue(cart.getItem(0).isEmpty() && donkey.getInventory().getItem(0).isEmpty()
+                        && zombie.getItemBySlot(EquipmentSlot.MAINHAND).isEmpty(),
+                "Disarm must remove inventory contents and worn equipment");
+        var drops = level.getEntitiesOfClass(ItemEntity.class, new AABB(source, source).inflate(3));
+        helper.assertTrue(drops.stream().anyMatch(item -> item.getItem().is(Items.EMERALD))
+                        && drops.stream().anyMatch(item -> item.getItem().is(Items.SADDLE))
+                        && drops.stream().anyMatch(item -> item.getItem().is(Items.IRON_SWORD)),
+                "Carrier items and guaranteed-drop mob equipment must remain at departure");
+        helper.succeed();
+    }
+}

src/main/java/net/dnorberg/rivencraft/book/LinkProperties.java

@@ -11,11 +11,15 @@ import net.minecraft.network.chat.Component;
 /** Flags written into a Link Panel and carried by books assembled from it. */
 public record LinkProperties(int flags) {
     public static final int DISARM = 1;
-    /** Retained only to read pre-0.4.7.1 test books; no longer generated or applied. */
+    /** Linking Books do not create a platform unless this Legacy flag is enabled. */
     public static final int GENERATE_PLATFORM = 2;
     public static final int MAINTAIN_MOMENTUM = 4;
     public static final int INTRA_LINKING = 8;
-    private static final int ALL_FLAGS = DISARM | GENERATE_PLATFORM | MAINTAIN_MOMENTUM | INTRA_LINKING;
+    public static final int INTRA_LINKING_ONLY = 16;
+    public static final int RELATIVE_LINK = 32;
+    public static final int DISABLE_PLATFORM = 64;
+    private static final int ALL_FLAGS = DISARM | GENERATE_PLATFORM | MAINTAIN_MOMENTUM | INTRA_LINKING
+            | INTRA_LINKING_ONLY | RELATIVE_LINK | DISABLE_PLATFORM;
     public static final LinkProperties NONE = new LinkProperties(0);
     public static final Codec<LinkProperties> CODEC = Codec.intRange(0, ALL_FLAGS).xmap(
             LinkProperties::new, LinkProperties::flags);
@@ -35,13 +39,17 @@ public record LinkProperties(int flags) {
 
     /** Intra Linking only governs Linking Books; a Descriptive Book treats that panel as ordinary. */
     public LinkProperties forDescriptiveBook() {
-        return new LinkProperties(flags & ~INTRA_LINKING);
+        return new LinkProperties(flags & ~(INTRA_LINKING | INTRA_LINKING_ONLY));
     }
 
     public void appendTooltip(List<Component> lines) {
         if (has(DISARM)) lines.add(propertyName("disarm"));
         if (has(MAINTAIN_MOMENTUM)) lines.add(propertyName("maintain_momentum"));
         if (has(INTRA_LINKING)) lines.add(propertyName("intra_linking"));
+        if (has(INTRA_LINKING_ONLY)) lines.add(propertyName("intra_linking_only"));
+        if (has(RELATIVE_LINK)) lines.add(propertyName("relative_link"));
+        if (has(GENERATE_PLATFORM)) lines.add(propertyName("generate_platform"));
+        if (has(DISABLE_PLATFORM)) lines.add(propertyName("disable_platform"));
     }
 
     private static Component propertyName(String name) {
@@ -54,6 +62,10 @@ public record LinkProperties(int flags) {
             case DISARM -> propertyName("disarm");
             case MAINTAIN_MOMENTUM -> propertyName("maintain_momentum");
             case INTRA_LINKING -> propertyName("intra_linking");
+            case INTRA_LINKING_ONLY -> propertyName("intra_linking_only");
+            case RELATIVE_LINK -> propertyName("relative_link");
+            case GENERATE_PLATFORM -> propertyName("generate_platform");
+            case DISABLE_PLATFORM -> propertyName("disable_platform");
             default -> throw new IllegalArgumentException("Unknown link property flag: " + flag);
         };
     }

src/main/java/net/dnorberg/rivencraft/book/LinkVisualEffects.java

@@ -0,0 +1,41 @@
+package net.dnorberg.rivencraft.book;
+
+import net.dnorberg.rivencraft.registry.ModSounds;
+import net.minecraft.core.particles.ParticleTypes;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.sounds.SoundEvent;
+import net.minecraft.sounds.SoundSource;
+import net.minecraft.world.phys.Vec3;
+
+/** Legacy-style sound and particle bursts at both ends of a successful link. */
+public final class LinkVisualEffects {
+    private static final int PARTICLE_COUNT = 50;
+
+    private LinkVisualEffects() {}
+
+    public static SoundEvent sound(LinkProperties properties, boolean portal) {
+        // Legacy's Disarm flag takes precedence over a portal's sound override.
+        if (properties.has(LinkProperties.DISARM)) return ModSounds.LINK_DISARM.get();
+        if (portal) return ModSounds.LINK_PORTAL.get();
+        if (properties.has(LinkProperties.INTRA_LINKING)) return ModSounds.LINK_INTRA.get();
+        return ModSounds.LINK.get();
+    }
+
+    public static void play(ServerLevel source, Vec3 departure, ServerPlayer player,
+                            LinkProperties properties, boolean portal) {
+        SoundEvent event = sound(properties, portal);
+        burst(source, departure, event);
+        burst(player.serverLevel(), player.position(), event);
+    }
+
+    private static void burst(ServerLevel level, Vec3 position, SoundEvent event) {
+        level.playSound(null, position.x, position.y, position.z, event,
+                SoundSource.PLAYERS, 0.8F, level.random.nextFloat() * 0.2F + 0.9F);
+        // Legacy emitted 50 small neutral particles in a roughly one-by-two-
+        // block space. Cloud particles are a vanilla gray-white stand-in for
+        // its removed fixed-function particle class.
+        level.sendParticles(ParticleTypes.CLOUD, position.x, position.y, position.z,
+                PARTICLE_COUNT, 0.5, 1.0, 0.5, 0.005);
+    }
+}

src/main/java/net/dnorberg/rivencraft/book/LinkingService.java

@@ -5,14 +5,21 @@ import java.util.Optional;
 import java.util.stream.IntStream;
 import java.util.stream.Stream;
 import net.dnorberg.rivencraft.compat.ImmersivePortalsChunkLoaders;
+import net.dnorberg.rivencraft.entity.DroppedBookEntity;
+import net.dnorberg.rivencraft.portal.PortalTravelCooldown;
+import net.dnorberg.rivencraft.registry.ModBlocks;
 import net.minecraft.core.BlockPos;
 import net.minecraft.core.Direction;
 import net.minecraft.server.level.ServerLevel;
 import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.world.InteractionHand;
+import net.minecraft.world.entity.Entity;
+import net.minecraft.world.item.ItemStack;
 import net.minecraft.tags.BlockTags;
 import net.minecraft.world.level.border.WorldBorder;
 import net.minecraft.world.level.levelgen.Heightmap;
 import net.minecraft.world.phys.Vec3;
+import net.minecraft.world.level.portal.DimensionTransition;
 import net.neoforged.fml.ModList;
 
 /** Server-side validation and execution for book travel. */
@@ -29,7 +36,42 @@ public final class LinkingService {
     }
 
     public static LinkResult travel(ServerPlayer player, LinkTarget target, LinkProperties properties) {
-        return travel(player, target, false, properties);
+        return travel(player, target, false, properties, false);
+    }
+
+    /** Removes only the active handheld book after a successful link, leaving it at the departure point. */
+    public static LinkResult travelHandheld(ServerPlayer player, InteractionHand hand, ItemStack activeBook,
+                                            LinkTarget target, LinkProperties properties, boolean requiresFooting) {
+        if (player.getItemInHand(hand) != activeBook || activeBook.isEmpty()) {
+            return LinkResult.NO_SAFE_DESTINATION;
+        }
+
+        ServerLevel sourceLevel = player.serverLevel();
+        Vec3 sourcePosition = player.position();
+        player.setItemInHand(hand, ItemStack.EMPTY);
+        boolean dropped = false;
+        try {
+            LinkResult result = requiresFooting
+                    ? travelWithFooting(player, target, properties)
+                    : travel(player, target, properties);
+            if (result != LinkResult.SUCCESS) return result;
+
+            DroppedBookEntity book = new DroppedBookEntity(sourceLevel, sourcePosition, activeBook);
+            dropped = sourceLevel.addFreshEntity(book);
+            return result;
+        } finally {
+            // Failed validation or a rejected entity spawn must never eat the book.
+            if (!dropped) {
+                if (player.getItemInHand(hand).isEmpty()) player.setItemInHand(hand, activeBook);
+                else if (!player.getInventory().add(activeBook)) player.drop(activeBook, false);
+            }
+            player.containerMenu.broadcastChanges();
+        }
+    }
+
+    /** Portal travel uses the vanilla transfer if its destination is not yet loaded. */
+    public static LinkResult travelPortal(ServerPlayer player, LinkTarget target, LinkProperties properties) {
+        return travel(player, target, false, properties, true);
     }
 
     public static Optional<Vec3> resolveDestination(ServerLevel level, BlockPos origin, boolean ageArrival) {
@@ -48,89 +90,170 @@ public final class LinkingService {
         if (destinationLevel == null) {
             return LinkResult.MISSING_DIMENSION;
         }
-        Optional<Vec3> destination = resolveDestination(destinationLevel, target.location().pos(), true);
+        if (properties.has(LinkProperties.INTRA_LINKING_ONLY) && destinationLevel != player.serverLevel())
+            return LinkResult.INTRA_ONLY;
+        BlockPos origin = landingOrigin(player, destinationLevel, target, properties);
+        Optional<Vec3> destination = resolveDestination(destinationLevel, origin, true);
         if (destination.isEmpty()) {
             return LinkResult.NO_SAFE_DESTINATION;
         }
 
         Vec3 position = destination.get();
         Vec3 momentum = player.getDeltaMovement();
-        if (properties.has(LinkProperties.DISARM)) dropInventoryAtSource(player);
-        teleport(player, destinationLevel, position, target);
-        if (properties.has(LinkProperties.MAINTAIN_MOMENTUM)) player.setDeltaMovement(momentum);
+        if (properties.has(LinkProperties.DISARM)) LinkDisarmService.disarm(player);
+        teleport(player, destinationLevel, position, target, true);
+        applyMomentum(player, momentum, target, properties);
         player.resetFallDistance();
         return LinkResult.SUCCESS;
     }
 
-    /** A descriptive portal uses the book's Age destination without requiring a landing platform. */
+    /** A descriptive portal requires existing footing, but never generates a landing platform. */
     public static LinkResult travelDescriptivePortal(ServerPlayer player, LinkTarget target, LinkProperties properties) {
         ServerLevel destinationLevel = player.getServer().getLevel(target.location().dimension());
         if (destinationLevel == null) return LinkResult.MISSING_DIMENSION;
-        Optional<Vec3> destination = resolveDestination(destinationLevel, target.location().pos(), false);
+        boolean instant = destinationChunksLoaded(destinationLevel, target.location().pos());
+        if (properties.has(LinkProperties.INTRA_LINKING_ONLY) && destinationLevel != player.serverLevel())
+            return LinkResult.INTRA_ONLY;
+        Optional<Vec3> destination = resolveDestination(destinationLevel,
+                landingOrigin(player, destinationLevel, target, properties), true);
         if (destination.isEmpty()) return LinkResult.NO_SAFE_DESTINATION;
         Vec3 momentum = player.getDeltaMovement();
-        if (properties.has(LinkProperties.DISARM)) dropInventoryAtSource(player);
-        teleport(player, destinationLevel, destination.get(), target);
-        if (properties.has(LinkProperties.MAINTAIN_MOMENTUM)) player.setDeltaMovement(momentum);
+        if (properties.has(LinkProperties.DISARM)) LinkDisarmService.disarm(player);
+        teleport(player, destinationLevel, destination.get(), target, instant);
+        applyMomentum(player, momentum, target, properties);
         player.resetFallDistance();
         return LinkResult.SUCCESS;
     }
 
     private static LinkResult travel(ServerPlayer player, LinkTarget target, boolean requiresFooting,
-                                     LinkProperties properties) {
+                                     LinkProperties properties, boolean portal) {
         ServerLevel destinationLevel = player.getServer().getLevel(target.location().dimension());
         if (destinationLevel == null) {
             return LinkResult.MISSING_DIMENSION;
         }
-        if (destinationLevel == player.level() && !properties.has(LinkProperties.INTRA_LINKING))
+        if (properties.has(LinkProperties.INTRA_LINKING_ONLY) && destinationLevel != player.serverLevel())
+            return LinkResult.INTRA_ONLY;
+        if (destinationLevel == player.level() && !properties.has(LinkProperties.INTRA_LINKING)
+                && !properties.has(LinkProperties.INTRA_LINKING_ONLY))
             return LinkResult.INTRA_LINKING_REQUIRED;
 
-        Optional<Vec3> destination = resolveDestination(destinationLevel, target.location().pos(), requiresFooting);
+        boolean instant = !portal || destinationChunksLoaded(destinationLevel, target.location().pos());
+        Optional<Vec3> destination = resolveDestination(destinationLevel,
+                landingOrigin(player, destinationLevel, target, properties), requiresFooting);
         if (destination.isEmpty()) {
             return LinkResult.NO_SAFE_DESTINATION;
         }
 
         Vec3 position = destination.get();
         Vec3 momentum = player.getDeltaMovement();
-        if (properties.has(LinkProperties.DISARM)) dropInventoryAtSource(player);
-        teleport(player, destinationLevel, position, target);
-        if (properties.has(LinkProperties.MAINTAIN_MOMENTUM)) player.setDeltaMovement(momentum);
+        if (properties.has(LinkProperties.DISARM)) LinkDisarmService.disarm(player);
+        teleport(player, destinationLevel, position, target, instant);
+        if (properties.has(LinkProperties.GENERATE_PLATFORM))
+            generateArrivalPlatform(destinationLevel, position);
+        applyMomentum(player, momentum, target, properties);
         player.resetFallDistance();
         return LinkResult.SUCCESS;
     }
 
-    /** Drop each inventory stack as an item entity at the departure point. */
-    private static void dropInventoryAtSource(ServerPlayer player) {
-        var inventory = player.getInventory();
-        for (int slot = 0; slot < inventory.getContainerSize(); slot++) {
-            var stack = inventory.getItem(slot);
-            if (stack.isEmpty()) continue;
-            inventory.setItem(slot, net.minecraft.world.item.ItemStack.EMPTY);
-            player.drop(stack, false);
-        }
-        player.containerMenu.broadcastChanges();
+    /** Non-player portal travel follows the same link rules; Disarm may remove carried cargo. */
+    public static LinkResult travelEntityPortal(Entity entity, LinkTarget target,
+                                                LinkProperties properties, boolean requiresFooting) {
+        if (!(entity.level() instanceof ServerLevel source)) return LinkResult.MISSING_DIMENSION;
+        ServerLevel destinationLevel = source.getServer().getLevel(target.location().dimension());
+        if (destinationLevel == null) return LinkResult.MISSING_DIMENSION;
+        if (properties.has(LinkProperties.INTRA_LINKING_ONLY) && destinationLevel != source)
+            return LinkResult.INTRA_ONLY;
+        if (destinationLevel == source && !properties.has(LinkProperties.INTRA_LINKING)
+                && !properties.has(LinkProperties.INTRA_LINKING_ONLY)) return LinkResult.INTRA_LINKING_REQUIRED;
+        if (properties.has(LinkProperties.DISARM) && !LinkDisarmService.mayTravel(entity))
+            return LinkResult.DISARM_REJECTED;
+        if (!entity.canChangeDimensions(source, destinationLevel)) return LinkResult.NO_SAFE_DESTINATION;
+        BlockPos origin = landingOrigin(entity, destinationLevel, target, properties);
+        Optional<Vec3> destination = resolveDestination(destinationLevel, origin, requiresFooting);
+        if (destination.isEmpty()) return LinkResult.NO_SAFE_DESTINATION;
+
+        Vec3 momentum = entity.getDeltaMovement();
+        if (properties.has(LinkProperties.DISARM)) LinkDisarmService.disarm(entity);
+        Entity arrived = entity.changeDimension(new DimensionTransition(destinationLevel, destination.get(),
+                properties.has(LinkProperties.MAINTAIN_MOMENTUM)
+                        ? rotatedMomentum(momentum, target.yaw()) : Vec3.ZERO,
+                target.yaw(), target.pitch(), DimensionTransition.DO_NOTHING));
+        if (arrived == null) return LinkResult.NO_SAFE_DESTINATION;
+        if (!requiresFooting && properties.has(LinkProperties.GENERATE_PLATFORM))
+            generateArrivalPlatform(destinationLevel, destination.get());
+        arrived.setXRot(target.pitch());
+        arrived.resetFallDistance();
+        PortalTravelCooldown.mark(arrived, source.getServer().getTickCount());
+        return LinkResult.SUCCESS;
+    }
+
+    static Vec3 rotatedMomentum(Vec3 incoming, float destinationYaw) {
+        // Legacy rotates the horizontal speed to the destination yaw and adds a small upward lift.
+        double horizontalSpeed = Math.hypot(incoming.x, incoming.z);
+        double radians = Math.toRadians(destinationYaw);
+        return new Vec3(horizontalSpeed * Math.cos(radians), incoming.y + 0.2,
+                horizontalSpeed * Math.sin(radians));
+    }
+
+    private static void applyMomentum(ServerPlayer player, Vec3 incoming, LinkTarget target,
+                                      LinkProperties properties) {
+        player.setDeltaMovement(properties.has(LinkProperties.MAINTAIN_MOMENTUM)
+                ? rotatedMomentum(incoming, target.yaw()) : Vec3.ZERO);
+    }
+
+    private static void generateArrivalPlatform(ServerLevel level, Vec3 arrival) {
+        BlockPos feet = BlockPos.containing(arrival);
+        BlockPos floor = feet.below();
+        // Legacy only fills a missing floor when there is clear space above the arrival.
+        if (level.isEmptyBlock(floor) && level.isEmptyBlock(feet.above(2)))
+            level.setBlock(floor, ModBlocks.CLOUD_PLATFORM.get().defaultBlockState(), 3);
+    }
+
+    /** Legacy relative links retain the traveller's offset from the source spawn. */
+    private static BlockPos landingOrigin(Entity player, ServerLevel destinationLevel,
+                                          LinkTarget target, LinkProperties properties) {
+        if (!properties.has(LinkProperties.RELATIVE_LINK)) return target.location().pos();
+        BlockPos sourceSpawn = ((ServerLevel) player.level()).getSharedSpawnPos();
+        BlockPos destinationSpawn = destinationLevel.getSharedSpawnPos();
+        BlockPos departure = player.blockPosition();
+        return destinationSpawn.offset(departure.getX() - sourceSpawn.getX(),
+                departure.getY() - sourceSpawn.getY(), departure.getZ() - sourceSpawn.getZ());
     }
 
     private static void teleport(
             ServerPlayer player,
             ServerLevel destinationLevel,
             Vec3 position,
-            LinkTarget target
+            LinkTarget target,
+            boolean instant
     ) {
         if (ModList.get().isLoaded("immersive_portals_core")) {
             ImmersivePortalsChunkLoaders.close(player);
-            ImmersivePortalsChunkLoaders.teleport(
-                    player, destinationLevel, position, target.yaw(), target.pitch());
-        } else {
-            player.teleportTo(
-                    destinationLevel,
-                    position.x,
-                    position.y,
-                    position.z,
-                    target.yaw(),
-                    target.pitch()
-            );
+            if (instant) {
+                ImmersivePortalsChunkLoaders.teleport(
+                        player, destinationLevel, position, target.yaw(), target.pitch());
+                return;
+            }
         }
+        player.teleportTo(
+                destinationLevel,
+                position.x,
+                position.y,
+                position.z,
+                target.yaw(),
+                target.pitch()
+        );
+    }
+
+    private static boolean destinationChunksLoaded(ServerLevel level, BlockPos center) {
+        int chunkX = center.getX() >> 4;
+        int chunkZ = center.getZ() >> 4;
+        for (int x = chunkX - 1; x <= chunkX + 1; x++) {
+            for (int z = chunkZ - 1; z <= chunkZ + 1; z++) {
+                if (!level.getChunkSource().hasChunk(x, z)) return false;
+            }
+        }
+        return true;
     }
 
     static Optional<Vec3> findSafeDestination(ServerLevel level, BlockPos origin) {
@@ -209,6 +332,8 @@ public final class LinkingService {
         SUCCESS,
         MISSING_DIMENSION,
         INTRA_LINKING_REQUIRED,
+        INTRA_ONLY,
+        DISARM_REJECTED,
         NO_SAFE_DESTINATION
     }
 }

src/main/java/net/dnorberg/rivencraft/client/BookReceptacleRenderer.java

@@ -0,0 +1,67 @@
+package net.dnorberg.rivencraft.client;
+
+import com.mojang.blaze3d.vertex.PoseStack;
+import com.mojang.blaze3d.vertex.VertexConsumer;
+import com.mojang.math.Axis;
+import net.dnorberg.rivencraft.block.BookReceptacleBlock;
+import net.dnorberg.rivencraft.block.entity.BookReceptacleBlockEntity;
+import net.dnorberg.rivencraft.registry.ModItems;
+import net.minecraft.client.model.BookModel;
+import net.minecraft.client.model.geom.ModelLayers;
+import net.minecraft.client.renderer.MultiBufferSource;
+import net.minecraft.client.renderer.RenderType;
+import net.minecraft.client.renderer.blockentity.BlockEntityRenderer;
+import net.minecraft.client.renderer.blockentity.BlockEntityRendererProvider;
+import net.minecraft.core.Direction;
+import net.minecraft.resources.ResourceLocation;
+
+/** Legacy's almost-closed book, oriented to the receptacle's mounting face. */
+public final class BookReceptacleRenderer implements BlockEntityRenderer<BookReceptacleBlockEntity> {
+    private static final ResourceLocation LINKING_TEXTURE = ResourceLocation.fromNamespaceAndPath(
+            "rivencraft", "textures/entity/linking_book.png");
+    private static final ResourceLocation DESCRIPTIVE_TEXTURE = ResourceLocation.fromNamespaceAndPath(
+            "rivencraft", "textures/entity/descriptive_book.png");
+    private final BookModel model;
+
+    public BookReceptacleRenderer(BlockEntityRendererProvider.Context context) {
+        model = new BookModel(context.bakeLayer(ModelLayers.BOOK));
+    }
+
+    @Override
+    public void render(BookReceptacleBlockEntity receptacle, float partialTick, PoseStack poseStack,
+                       MultiBufferSource buffers, int packedLight, int packedOverlay) {
+        if (receptacle.getBook().isEmpty()) return;
+
+        poseStack.pushPose();
+        poseStack.translate(0.5, 0.5, 0.5);
+        Direction facing = receptacle.getBlockState().getValue(BookReceptacleBlock.FACING);
+        switch (facing) {
+            case UP -> {
+                // Rotate the whole assembled top-mounted receptacle/book pair
+                // around the block center, matching the x=90 block model.
+                poseStack.mulPose(Axis.ZP.rotationDegrees(180));
+                poseStack.mulPose(Axis.XP.rotationDegrees(-90));
+                poseStack.mulPose(Axis.YP.rotationDegrees(90));
+                // Preserve the local half-turn that seats the book in its slot.
+                poseStack.mulPose(Axis.ZP.rotationDegrees(180));
+            }
+            case DOWN -> {
+                // The ceiling-mounted model is the inverted top assembly.
+                poseStack.mulPose(Axis.XP.rotationDegrees(-90));
+                poseStack.mulPose(Axis.YP.rotationDegrees(90));
+                poseStack.mulPose(Axis.ZP.rotationDegrees(180));
+            }
+            case NORTH -> poseStack.mulPose(Axis.YP.rotationDegrees(-90));
+            case SOUTH -> poseStack.mulPose(Axis.YP.rotationDegrees(90));
+            case EAST -> poseStack.mulPose(Axis.YP.rotationDegrees(180));
+            case WEST -> { }
+        }
+        poseStack.scale(0.8F, 0.8F, 0.8F);
+        model.setupAnim(0.0F, 0.1F, 0.1F, 0.005F);
+        ResourceLocation texture = receptacle.getBook().is(ModItems.DESCRIPTIVE_BOOK.get())
+                ? DESCRIPTIVE_TEXTURE : LINKING_TEXTURE;
+        VertexConsumer vertices = buffers.getBuffer(RenderType.entitySolid(texture));
+        model.render(poseStack, vertices, packedLight, packedOverlay, -1);
+        poseStack.popPose();
+    }
+}

src/main/java/net/dnorberg/rivencraft/client/ClientAgeCelestialAngles.java

@@ -2,23 +2,58 @@ package net.dnorberg.rivencraft.client;
 
 import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
+import net.dnorberg.rivencraft.book.AgeSkyProfile;
 import net.dnorberg.rivencraft.network.AgeCelestialAnglePayload;
 import net.minecraft.resources.ResourceKey;
 import net.minecraft.world.level.Level;
 import net.neoforged.neoforge.network.handling.IPayloadContext;
+import net.neoforged.neoforge.network.PacketDistributor;
+import net.dnorberg.rivencraft.network.RequestAgeSkyPayload;
 
 /** Client cache used by both the active world and remote preview renderers. */
 public final class ClientAgeCelestialAngles {
     private static final Map<ResourceKey<Level>, Float> ANGLES = new ConcurrentHashMap<>();
+    private static final Map<ResourceKey<Level>, AgeSkyProfile> SKIES = new ConcurrentHashMap<>();
+    private static final Map<ResourceKey<Level>, Long> LAST_REQUEST = new ConcurrentHashMap<>();
 
     private ClientAgeCelestialAngles() {
     }
 
     public static void handle(AgeCelestialAnglePayload payload, IPayloadContext context) {
         ANGLES.put(payload.dimension(), payload.angle());
+        SKIES.put(payload.dimension(), payload.sky());
+        LAST_REQUEST.remove(payload.dimension());
+    }
+
+    public static void requestIfMissing(ResourceKey<Level> dimension) {
+        if (!dimension.location().getNamespace().equals("rivencraft") || SKIES.containsKey(dimension)) return;
+        long now = System.nanoTime();
+        Long previous = LAST_REQUEST.putIfAbsent(dimension, now);
+        if (previous != null && now - previous < 2_000_000_000L) return;
+        LAST_REQUEST.put(dimension, now);
+        PacketDistributor.sendToServer(new RequestAgeSkyPayload(dimension));
+    }
+
+    public static void clear() {
+        ANGLES.clear();
+        SKIES.clear();
+        LAST_REQUEST.clear();
     }
 
     public static float get(ResourceKey<Level> dimension) {
         return ANGLES.getOrDefault(dimension, 0.0F);
     }
+
+    public static int skyColor(ResourceKey<Level> dimension) {
+        return sky(dimension).color();
+    }
+
+    public static boolean staticSky(ResourceKey<Level> dimension) {
+        return sky(dimension).style() == AgeSkyProfile.Style.STATIC;
+    }
+
+    public static AgeSkyProfile sky(ResourceKey<Level> dimension) {
+        return SKIES.getOrDefault(dimension,
+                new AgeSkyProfile(AgeSkyProfile.Style.INHERITED, -1, java.util.List.of()));
+    }
 }

src/main/java/net/dnorberg/rivencraft/client/ClientEvents.java

@@ -5,6 +5,7 @@ import net.dnorberg.rivencraft.registry.ModBlockEntities;
 import net.dnorberg.rivencraft.registry.ModBlocks;
 import net.dnorberg.rivencraft.registry.ModDataComponents;
 import net.dnorberg.rivencraft.registry.ModItems;
+import net.dnorberg.rivencraft.registry.ModEntities;
 import net.minecraft.client.renderer.item.ItemProperties;
 import net.minecraft.client.renderer.ItemBlockRenderTypes;
 import net.minecraft.client.renderer.RenderType;
@@ -18,6 +19,12 @@ import net.neoforged.neoforge.common.NeoForge;
 import net.neoforged.neoforge.client.event.EntityRenderersEvent;
 import net.neoforged.neoforge.client.event.RegisterMenuScreensEvent;
 import net.neoforged.neoforge.client.event.RegisterClientReloadListenersEvent;
+import net.neoforged.neoforge.client.event.RegisterDimensionSpecialEffectsEvent;
+import net.neoforged.neoforge.client.event.RegisterColorHandlersEvent;
+import net.neoforged.neoforge.client.event.ClientPlayerNetworkEvent;
+import net.dnorberg.rivencraft.block.entity.CrystalPortalBlockEntity;
+import net.dnorberg.rivencraft.block.entity.BookReceptacleBlockEntity;
+import net.dnorberg.rivencraft.book.AgeEnvironmentCompiler;
 import net.neoforged.neoforge.client.extensions.common.IClientItemExtensions;
 import net.neoforged.neoforge.client.extensions.common.RegisterClientExtensionsEvent;
 import net.minecraft.client.renderer.BlockEntityWithoutLevelRenderer;
@@ -25,6 +32,7 @@ import net.dnorberg.rivencraft.client.screen.NotebookScreen;
 import net.dnorberg.rivencraft.client.screen.WritingDeskScreen;
 import net.dnorberg.rivencraft.client.screen.BookBinderScreen;
 import net.dnorberg.rivencraft.client.screen.InkMixerScreen;
+import net.dnorberg.rivencraft.client.screen.LinkModifierScreen;
 import net.dnorberg.rivencraft.registry.ModMenus;
 
 @EventBusSubscriber(modid = Rivencraft.MOD_ID, value = Dist.CLIENT)
@@ -34,17 +42,37 @@ public final class ClientEvents {
 
     @SubscribeEvent
     public static void registerRenderers(EntityRenderersEvent.RegisterRenderers event) {
+        event.registerEntityRenderer(ModEntities.DROPPED_BOOK.get(), DroppedBookRenderer::new);
         event.registerBlockEntityRenderer(ModBlockEntities.BOOK_STAND.get(), BookStandRenderer::new);
+        event.registerBlockEntityRenderer(ModBlockEntities.BOOK_RECEPTACLE.get(), BookReceptacleRenderer::new);
         event.registerBlockEntityRenderer(ModBlockEntities.WRITING_DESK.get(), WritingDeskRenderer::new);
         event.registerBlockEntityRenderer(ModBlockEntities.STAR_FISSURE.get(), StarFissureRenderer::new);
     }
 
+    @SubscribeEvent
+    public static void registerSkyEffects(RegisterDimensionSpecialEffectsEvent event) {
+        event.register(AgeEnvironmentCompiler.CUSTOM_SKY_EFFECTS, new RivencraftSkyEffects());
+    }
+
+    @SubscribeEvent
+    public static void registerPortalColor(RegisterColorHandlersEvent.Block event) {
+        event.register((state, level, pos, tintIndex) -> {
+            if (level == null || pos == null || tintIndex != 0
+                    || !(level.getBlockEntity(pos) instanceof CrystalPortalBlockEntity portal)
+                    || portal.receptacle() == null
+                    || !(level.getBlockEntity(portal.receptacle()) instanceof BookReceptacleBlockEntity holder)
+                    || holder.destination() == null) return 0xFFFFFF;
+            return holder.skyColor();
+        }, ModBlocks.CRYSTAL_PORTAL.get());
+    }
+
     @SubscribeEvent
     public static void registerScreens(RegisterMenuScreensEvent event) {
         event.register(ModMenus.NOTEBOOK.get(), NotebookScreen::new);
         event.register(ModMenus.WRITING_DESK.get(), WritingDeskScreen::new);
         event.register(ModMenus.BOOK_BINDER.get(), BookBinderScreen::new);
         event.register(ModMenus.INK_MIXER.get(), InkMixerScreen::new);
+        event.register(ModMenus.LINK_MODIFIER.get(), LinkModifierScreen::new);
     }
 
     @SubscribeEvent
@@ -78,13 +106,15 @@ public final class ClientEvents {
             ItemBlockRenderTypes.setRenderLayer(ModBlocks.MEDIUM_CRYSTAL_BUD.get(), RenderType.cutout());
             ItemBlockRenderTypes.setRenderLayer(ModBlocks.LARGE_CRYSTAL_BUD.get(), RenderType.cutout());
             ItemBlockRenderTypes.setRenderLayer(ModBlocks.CRYSTAL_CLUSTER.get(), RenderType.cutout());
-            ItemBlockRenderTypes.setRenderLayer(ModBlocks.CLOUD_PLATFORM.get(), RenderType.translucent());
+            ItemBlockRenderTypes.setRenderLayer(ModBlocks.INK_MIXER.get(), RenderType.cutout());
             ItemBlockRenderTypes.setRenderLayer(ModBlocks.CRYSTAL_PORTAL.get(), RenderType.translucent());
             // Immersive Portals composes the remote view before translucent blocks.
             // Draw the opaque crystal frame in that later pass so it masks the view;
             // the portal cell itself is invisible while its live view is active.
             if (ModList.get().isLoaded("immersive_portals_core"))
                 ItemBlockRenderTypes.setRenderLayer(ModBlocks.CRYSTAL_BLOCK.get(), RenderType.translucent());
+            if (ModList.get().isLoaded("create"))
+                net.dnorberg.rivencraft.compat.RivencraftPonderGuide.register();
         });
         NeoForge.EVENT_BUS.addListener(ClientBookInteractionHandler::onRightClickItem);
         NeoForge.EVENT_BUS.addListener(ClientBookInteractionHandler::onRightClickBlock);
@@ -92,6 +122,11 @@ public final class ClientEvents {
         NeoForge.EVENT_BUS.addListener(ClientBookExploreOverlay::onClientTickPost);
         NeoForge.EVENT_BUS.addListener(ClientBookExploreOverlay::onRenderGui);
         NeoForge.EVENT_BUS.addListener(ClientBookExploreOverlay::onMouseButton);
+        NeoForge.EVENT_BUS.addListener(ClientEvents::onLogout);
+    }
+
+    private static void onLogout(ClientPlayerNetworkEvent.LoggingOut event) {
+        ClientAgeCelestialAngles.clear();
     }
 
 }

src/main/java/net/dnorberg/rivencraft/client/DroppedBookRenderer.java

@@ -0,0 +1,51 @@
+package net.dnorberg.rivencraft.client;
+
+import com.mojang.blaze3d.vertex.PoseStack;
+import com.mojang.blaze3d.vertex.VertexConsumer;
+import com.mojang.math.Axis;
+import net.dnorberg.rivencraft.entity.DroppedBookEntity;
+import net.dnorberg.rivencraft.registry.ModItems;
+import net.minecraft.client.model.BookModel;
+import net.minecraft.client.model.geom.ModelLayers;
+import net.minecraft.client.renderer.MultiBufferSource;
+import net.minecraft.client.renderer.RenderType;
+import net.minecraft.client.renderer.entity.EntityRenderer;
+import net.minecraft.client.renderer.entity.EntityRendererProvider;
+import net.minecraft.resources.ResourceLocation;
+
+/** Renders the same open book model and textures as Rivencraft's book stands. */
+public final class DroppedBookRenderer extends EntityRenderer<DroppedBookEntity> {
+    private static final ResourceLocation LINKING_TEXTURE = ResourceLocation.fromNamespaceAndPath(
+            "rivencraft", "textures/entity/linking_book.png");
+    private static final ResourceLocation DESCRIPTIVE_TEXTURE = ResourceLocation.fromNamespaceAndPath(
+            "rivencraft", "textures/entity/descriptive_book.png");
+    private final BookModel model;
+
+    public DroppedBookRenderer(EntityRendererProvider.Context context) {
+        super(context);
+        model = new BookModel(context.bakeLayer(ModelLayers.BOOK));
+        shadowRadius = 0.25F;
+    }
+
+    @Override
+    public void render(DroppedBookEntity entity, float yaw, float partialTick, PoseStack poseStack,
+                       MultiBufferSource buffers, int packedLight) {
+        poseStack.pushPose();
+        poseStack.translate(0.0F, 0.0625F, 0.0F);
+        poseStack.mulPose(Axis.YP.rotationDegrees(yaw + 90.0F));
+        // The opened model's covers rotate toward the YZ plane. As in Legacy's
+        // dropped-book renderer, a Z-axis quarter-turn lays the pages skyward.
+        poseStack.mulPose(Axis.ZP.rotationDegrees(90.0F));
+        poseStack.scale(0.8F, 0.8F, 0.8F);
+        model.setupAnim(0.0F, 0.0F, 0.0F, 1.2F);
+        VertexConsumer vertices = buffers.getBuffer(RenderType.entitySolid(getTextureLocation(entity)));
+        model.render(poseStack, vertices, packedLight, net.minecraft.client.renderer.texture.OverlayTexture.NO_OVERLAY, -1);
+        poseStack.popPose();
+        super.render(entity, yaw, partialTick, poseStack, buffers, packedLight);
+    }
+
+    @Override
+    public ResourceLocation getTextureLocation(DroppedBookEntity entity) {
+        return entity.getItem().is(ModItems.DESCRIPTIVE_BOOK.get()) ? DESCRIPTIVE_TEXTURE : LINKING_TEXTURE;
+    }
+}

src/main/java/net/dnorberg/rivencraft/client/RivencraftSkyEffects.java

@@ -0,0 +1,145 @@
+package net.dnorberg.rivencraft.client;
+
+import com.mojang.blaze3d.systems.RenderSystem;
+import com.mojang.blaze3d.vertex.BufferBuilder;
+import com.mojang.blaze3d.vertex.BufferUploader;
+import com.mojang.blaze3d.vertex.DefaultVertexFormat;
+import com.mojang.blaze3d.vertex.PoseStack;
+import com.mojang.blaze3d.vertex.Tesselator;
+import com.mojang.blaze3d.vertex.VertexFormat;
+import java.util.Random;
+import net.dnorberg.rivencraft.book.AgeSkyProfile;
+import net.minecraft.client.Camera;
+import net.minecraft.client.multiplayer.ClientLevel;
+import net.minecraft.client.renderer.DimensionSpecialEffects;
+import net.minecraft.client.renderer.FogRenderer;
+import net.minecraft.client.renderer.GameRenderer;
+import net.minecraft.world.phys.Vec3;
+import org.joml.Matrix4f;
+import com.mojang.math.Axis;
+import net.minecraft.resources.ResourceLocation;
+
+/** An authored sky can use vanilla celestial rendering or Legacy-style moving TV static. */
+public final class RivencraftSkyEffects extends DimensionSpecialEffects {
+    private static final int GRID = 16;
+    private static final float RADIUS = 100.0F;
+    private static final ResourceLocation SUN = ResourceLocation.withDefaultNamespace("textures/environment/sun.png");
+    private static final ResourceLocation MOON = ResourceLocation.withDefaultNamespace("textures/environment/moon_phases.png");
+
+    public RivencraftSkyEffects() {
+        super(192.0F, true, SkyType.NORMAL, false, false);
+    }
+
+    @Override
+    public Vec3 getBrightnessDependentFogColor(Vec3 color, float brightness) {
+        return color.multiply(brightness * 0.94F + 0.06F,
+                brightness * 0.94F + 0.06F, brightness * 0.91F + 0.09F);
+    }
+
+    @Override
+    public boolean isFoggyAt(int x, int y) {
+        return false;
+    }
+
+    @Override
+    public boolean renderSky(ClientLevel level, int ticks, float partialTick, Matrix4f modelViewMatrix,
+                             Camera camera, Matrix4f projectionMatrix, boolean isFoggy, Runnable setupFog) {
+        AgeSkyProfile sky = ClientAgeCelestialAngles.sky(level.dimension());
+        if (sky.style() != AgeSkyProfile.Style.STATIC && sky.color() == -1 && sky.bodies().isEmpty()
+                && sky.style() != AgeSkyProfile.Style.NETHER && sky.style() != AgeSkyProfile.Style.END)
+            return false;
+        setupFog.run();
+        if (isFoggy) return true;
+
+        PoseStack pose = new PoseStack();
+        pose.mulPose(modelViewMatrix);
+        Matrix4f matrix = pose.last().pose();
+        Random random = new Random((level.getGameTime() + (long) ticks) / 2L);
+        int tint = sky.color();
+        if (tint == -1) tint = switch (sky.style()) {
+            case NETHER -> 0x6B2725;
+            case END -> 0x211835;
+            case STATIC -> 0x929292;
+            default -> level.getBiome(camera.getBlockPosition()).value().getSkyColor();
+        };
+
+        RenderSystem.depthMask(false);
+        RenderSystem.disableCull();
+        RenderSystem.setShader(GameRenderer::getPositionColorShader);
+        RenderSystem.setShaderColor(1.0F, 1.0F, 1.0F, 1.0F);
+        FogRenderer.setupNoFog();
+        BufferBuilder vertices = Tesselator.getInstance().begin(
+                VertexFormat.Mode.QUADS, DefaultVertexFormat.POSITION_COLOR);
+        for (int axis = 0; axis < 3; axis++) {
+            for (int sign : new int[]{-1, 1}) {
+                for (int x = 0; x < GRID; x++) {
+                    for (int y = 0; y < GRID; y++) {
+                        int noise = sky.style() == AgeSkyProfile.Style.STATIC
+                                ? 65 + random.nextInt(160) : 255;
+                        int red = ((tint >> 16) & 255) * noise / 255;
+                        int green = ((tint >> 8) & 255) * noise / 255;
+                        int blue = (tint & 255) * noise / 255;
+                        int color = 0xFF000000 | red << 16 | green << 8 | blue;
+                        float left = -RADIUS + x * (2 * RADIUS / GRID);
+                        float right = -RADIUS + (x + 1) * (2 * RADIUS / GRID);
+                        float bottom = -RADIUS + y * (2 * RADIUS / GRID);
+                        float top = -RADIUS + (y + 1) * (2 * RADIUS / GRID);
+                        vertex(vertices, matrix, axis, sign, left, bottom, color);
+                        vertex(vertices, matrix, axis, sign, right, bottom, color);
+                        vertex(vertices, matrix, axis, sign, right, top, color);
+                        vertex(vertices, matrix, axis, sign, left, top, color);
+                    }
+                }
+            }
+        }
+        BufferUploader.drawWithShader(vertices.buildOrThrow());
+        if (!sky.bodies().isEmpty()) {
+            RenderSystem.enableBlend();
+            RenderSystem.defaultBlendFunc();
+            double time = level.getGameTime() + partialTick;
+            for (AgeSkyProfile.Body body : sky.bodies()) drawBody(pose, body, time);
+            RenderSystem.disableBlend();
+        }
+        setupFog.run();
+        RenderSystem.enableCull();
+        RenderSystem.depthMask(true);
+        return true;
+    }
+
+    private static void drawBody(PoseStack pose, AgeSkyProfile.Body body, double time) {
+        pose.pushPose();
+        pose.mulPose(Axis.YP.rotationDegrees(body.angle()));
+        double orbit = body.period() == 0 ? body.phase()
+                : (body.clockwise() ? 1.0D : -1.0D) * time
+                        / (24000.0D * body.period()) + body.phase();
+        pose.mulPose(Axis.XP.rotationDegrees((float) (orbit * 360.0D)));
+        float size = (body.kind() == AgeSkyProfile.Kind.SUN ? 30.0F : 20.0F) * body.size();
+        int color = body.color();
+        RenderSystem.setShader(GameRenderer::getPositionTexShader);
+        RenderSystem.setShaderTexture(0, body.kind() == AgeSkyProfile.Kind.SUN ? SUN : MOON);
+        RenderSystem.setShaderColor(((color >> 16) & 255) / 255.0F,
+                ((color >> 8) & 255) / 255.0F, (color & 255) / 255.0F, 1.0F);
+        float uMax = body.kind() == AgeSkyProfile.Kind.SUN ? 1.0F : 0.25F;
+        float vMax = body.kind() == AgeSkyProfile.Kind.SUN ? 1.0F : 0.5F;
+        BufferBuilder vertices = Tesselator.getInstance().begin(VertexFormat.Mode.QUADS,
+                DefaultVertexFormat.POSITION_TEX);
+        Matrix4f matrix = pose.last().pose();
+        vertices.addVertex(matrix, -size, RADIUS - 1.0F, -size).setUv(0.0F, 0.0F);
+        vertices.addVertex(matrix, size, RADIUS - 1.0F, -size).setUv(uMax, 0.0F);
+        vertices.addVertex(matrix, size, RADIUS - 1.0F, size).setUv(uMax, vMax);
+        vertices.addVertex(matrix, -size, RADIUS - 1.0F, size).setUv(0.0F, vMax);
+        BufferUploader.drawWithShader(vertices.buildOrThrow());
+        RenderSystem.setShaderColor(1.0F, 1.0F, 1.0F, 1.0F);
+        pose.popPose();
+    }
+
+    private static void vertex(BufferBuilder vertices, Matrix4f matrix, int axis, int sign,
+                               float x, float y, int color) {
+        float fixed = sign * RADIUS;
+        switch (axis) {
+            case 0 -> vertices.addVertex(matrix, fixed, x, y).setColor(color);
+            case 1 -> vertices.addVertex(matrix, x, fixed, y).setColor(color);
+            default -> vertices.addVertex(matrix, x, y, fixed).setColor(color);
+        }
+    }
+}

src/main/java/net/dnorberg/rivencraft/client/SymbolPageTextures.java

@@ -196,7 +196,7 @@ public final class SymbolPageTextures {
         graphics.setColor(1F, 1F, 1F, 1F);
     }
 
-    /** Legacy's single-number marks; numbers above 24 use positional base 25. */
+    /** Overlay each Legacy digit's components; place base-25 digits side by side. */
     public static void drawNumeral(GuiGraphics graphics, int number, int x, int y, int size) {
         int[] digits = SymbolNumerals.digitsFor(number);
         int digitSize = digits.length == 1 ? size : Math.max(8, size * 3 / 4);

src/main/java/net/dnorberg/rivencraft/client/screen/DescriptiveBookScreen.java

@@ -27,6 +27,7 @@ import net.minecraft.client.gui.components.Button;
 import net.minecraft.client.gui.components.EditBox;
 import net.minecraft.client.gui.components.Tooltip;
 import net.minecraft.network.chat.Component;
+import net.minecraft.core.component.DataComponents;
 import net.minecraft.resources.ResourceLocation;
 import net.minecraft.sounds.SoundEvents;
 import net.minecraft.util.FormattedCharSequence;
@@ -48,6 +49,7 @@ public final class DescriptiveBookScreen extends Screen implements ExplorableBoo
     private static final Component EXPLORE_ICON = Component.literal("👁");
 
     private final AgeReference age;
+    private final Component displayName;
     private final ResourceLocation generationProfile;
     private final AgeTraits traits;
     private final OrderedWriting writing;
@@ -68,6 +70,7 @@ public final class DescriptiveBookScreen extends Screen implements ExplorableBoo
                                  List<SymbolDisplayMetadata> writingSymbols) {
         super(book.getHoverName());
         age = book.get(ModDataComponents.AGE_REFERENCE.get());
+        displayName = book.get(DataComponents.CUSTOM_NAME);
         generationProfile = book.get(ModDataComponents.AGE_GENERATION_PROFILE.get());
         this.traits = traits;
         writing = book.getOrDefault(ModDataComponents.BOOK_WRITING.get(), OrderedWriting.EMPTY);
@@ -82,6 +85,7 @@ public final class DescriptiveBookScreen extends Screen implements ExplorableBoo
                                  List<SymbolDisplayMetadata> writingSymbols) {
         super(book.getHoverName());
         age = book.get(ModDataComponents.AGE_REFERENCE.get());
+        displayName = book.get(DataComponents.CUSTOM_NAME);
         generationProfile = book.get(ModDataComponents.AGE_GENERATION_PROFILE.get());
         this.traits = traits;
         writing = book.getOrDefault(ModDataComponents.BOOK_WRITING.get(), OrderedWriting.EMPTY);
@@ -245,7 +249,8 @@ public final class DescriptiveBookScreen extends Screen implements ExplorableBoo
             }
             return;
         }
-        int nameEnd = drawWrappedWithoutShadow(graphics, Component.literal(age.name()),
+        int nameEnd = drawWrappedWithoutShadow(graphics,
+                displayName == null ? Component.literal(age.name()) : displayName,
                 x, top + 40, 110);
         int detailsY = drawWrappedWithoutShadow(graphics,
                 author == null || author.isBlank()

src/main/java/net/dnorberg/rivencraft/client/screen/LinkModifierScreen.java

@@ -0,0 +1,193 @@
+package net.dnorberg.rivencraft.client.screen;
+
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.book.LinkProperties;
+import net.dnorberg.rivencraft.menu.LinkModifierMenu;
+import net.dnorberg.rivencraft.network.SetLinkModifierTitlePayload;
+import net.dnorberg.rivencraft.network.SetLinkModifierSeedPayload;
+import net.dnorberg.rivencraft.registry.ModDataComponents;
+import net.dnorberg.rivencraft.registry.ModItems;
+import net.minecraft.client.gui.GuiGraphics;
+import net.minecraft.client.gui.components.EditBox;
+import net.minecraft.client.gui.components.Tooltip;
+import net.minecraft.client.gui.screens.inventory.AbstractContainerScreen;
+import net.minecraft.core.component.DataComponents;
+import net.minecraft.network.chat.Component;
+import net.minecraft.resources.ResourceLocation;
+import net.minecraft.world.entity.player.Inventory;
+import net.minecraft.world.item.ItemStack;
+import net.neoforged.neoforge.network.PacketDistributor;
+
+/** Legacy single-slot layout, with server-owned link options. */
+public final class LinkModifierScreen extends AbstractContainerScreen<LinkModifierMenu> {
+    private static final ResourceLocation BACKGROUND = ResourceLocation.fromNamespaceAndPath(
+            Rivencraft.MOD_ID, "textures/gui/link_modifier_legacy.png");
+    private static final int[] FLAGS = {LinkProperties.DISARM, LinkProperties.INTRA_LINKING,
+            LinkProperties.INTRA_LINKING_ONLY, LinkProperties.MAINTAIN_MOMENTUM,
+            LinkProperties.RELATIVE_LINK, LinkProperties.DISABLE_PLATFORM};
+    private static final int[] IDS = {LinkModifierMenu.TOGGLE_DISARM, LinkModifierMenu.TOGGLE_INTRA,
+            LinkModifierMenu.TOGGLE_INTRA_ONLY, LinkModifierMenu.TOGGLE_MOMENTUM,
+            LinkModifierMenu.TOGGLE_RELATIVE, LinkModifierMenu.TOGGLE_PLATFORM};
+    private EditBox titleInput;
+    private EditBox seedInput;
+    private ItemStack lastBook = ItemStack.EMPTY;
+    private long lastSeed = Long.MIN_VALUE;
+
+    public LinkModifierScreen(LinkModifierMenu menu, Inventory inventory, Component title) {
+        super(menu, inventory, title);
+        imageWidth = 176;
+        imageHeight = 166;
+        inventoryLabelX = 8;
+        inventoryLabelY = 72;
+    }
+
+    @Override protected void init() {
+        super.init();
+        titleInput = new EditBox(font, leftPos + 80, topPos + 56, 87, 14,
+                Component.translatable("screen.rivencraft.link_modifier.title"));
+        titleInput.setMaxLength(32);
+        titleInput.setResponder(value -> PacketDistributor.sendToServer(
+                new SetLinkModifierTitlePayload(menu.containerId, value)));
+        addRenderableWidget(titleInput);
+        seedInput = new EditBox(font, leftPos + 80, topPos + 15, 87, 14,
+                Component.translatable("screen.rivencraft.link_modifier.seed"));
+        seedInput.setMaxLength(21);
+        seedInput.setTooltip(Tooltip.create(Component.translatable("screen.rivencraft.link_modifier.seed_warning")));
+        addRenderableWidget(seedInput);
+        refreshControls();
+    }
+
+    private void click(int id) {
+        if (minecraft != null && minecraft.gameMode != null)
+            minecraft.gameMode.handleInventoryButtonClick(menu.containerId, id);
+    }
+
+    @Override protected void containerTick() { refreshControls(); }
+
+    private void submitSeed() {
+        if (seedInput.visible && !seedInput.getValue().equals(Long.toString(menu.seed())))
+            PacketDistributor.sendToServer(new SetLinkModifierSeedPayload(menu.containerId, seedInput.getValue()));
+    }
+
+    @Override public boolean keyPressed(int keyCode, int scanCode, int modifiers) {
+        if (seedInput.isFocused()) {
+            if (keyCode == 257 || keyCode == 335) submitSeed();
+            else if (keyCode != 256) seedInput.keyPressed(keyCode, scanCode, modifiers);
+            if (keyCode == 256 || keyCode == 257 || keyCode == 335) {
+                setFocused(null);
+                seedInput.setFocused(false);
+            }
+            return true;
+        }
+        if (titleInput.isFocused()) {
+            if (keyCode == 256) {
+                setFocused(null);
+                titleInput.setFocused(false);
+            } else titleInput.keyPressed(keyCode, scanCode, modifiers);
+            return true;
+        }
+        return super.keyPressed(keyCode, scanCode, modifiers);
+    }
+
+    @Override public boolean mouseClicked(double mouseX, double mouseY, int button) {
+        if (seedInput.isFocused() && (mouseX < seedInput.getX() || mouseX >= seedInput.getX() + seedInput.getWidth()
+                || mouseY < seedInput.getY() || mouseY >= seedInput.getY() + seedInput.getHeight())) {
+            submitSeed();
+            setFocused(null);
+            seedInput.setFocused(false);
+        }
+        if (button == 0) {
+            for (int index = 0; index < FLAGS.length; index++) {
+                if (inside(mouseX, mouseY, 5 + (index / 3) * 20, 10 + (index % 3) * 20, 18, 18)) {
+                    if (!menu.book().isEmpty()) click(IDS[index]);
+                    return true;
+                }
+            }
+            if (menu.canDelete(minecraft.player)
+                    && inside(mouseX, mouseY, menu.awaitingDeletionConfirmation() ? 140 : 120, 32, 18, 18)) {
+                click(LinkModifierMenu.DELETE_AGE);
+                return true;
+            }
+        }
+        return super.mouseClicked(mouseX, mouseY, button);
+    }
+
+    private boolean inside(double mouseX, double mouseY, int x, int y, int width, int height) {
+        return mouseX >= leftPos + x && mouseX < leftPos + x + width
+                && mouseY >= topPos + y && mouseY < topPos + y + height;
+    }
+
+    private void refreshControls() {
+        ItemStack book = menu.book();
+        if (!ItemStack.isSameItemSameComponents(book, lastBook) && !titleInput.isFocused()) {
+            Component name = book.get(DataComponents.CUSTOM_NAME);
+            titleInput.setValue(name == null ? "" : name.getString());
+            lastBook = book.copy();
+        }
+        boolean present = !book.isEmpty();
+        titleInput.setEditable(present);
+        seedInput.visible = menu.hasSeed();
+        seedInput.setEditable(menu.hasSeed());
+        if (seedInput.visible && !seedInput.isFocused() && (lastSeed != menu.seed()
+                || !ItemStack.isSameItemSameComponents(book, lastBook))) {
+            lastSeed = menu.seed();
+            seedInput.setValue(Long.toString(lastSeed));
+        }
+    }
+
+    @Override protected void renderBg(GuiGraphics graphics, float partialTick, int mouseX, int mouseY) {
+        graphics.blit(BACKGROUND, leftPos, topPos, 0, 0, imageWidth, imageHeight, 256, 256);
+        LinkProperties properties = menu.book().getOrDefault(ModDataComponents.LINK_PROPERTIES.get(), LinkProperties.NONE);
+        for (int index = 0; index < FLAGS.length; index++) {
+            boolean selected = FLAGS[index] == LinkProperties.DISABLE_PLATFORM
+                    ? platformEnabled(properties) : properties.has(FLAGS[index]);
+            square(graphics, 5 + (index / 3) * 20, 10 + (index % 3) * 20,
+                    selected, false);
+        }
+        if (menu.canDelete(minecraft.player)) {
+            square(graphics, 120, 32, menu.awaitingDeletionConfirmation(), false);
+            if (menu.awaitingDeletionConfirmation()) square(graphics, 140, 32, false, true);
+        }
+    }
+
+    private void square(GuiGraphics graphics, int x, int y, boolean selected, boolean danger) {
+        int left = leftPos + x;
+        int top = topPos + y;
+        graphics.fill(left, top, left + 18, top + 18, 0xFFAAAAAA);
+        graphics.fill(left + 2, top + 2, left + 17, top + 17,
+                danger ? 0xFFAA5555 : selected ? 0xFFBBBBBB : 0xFF777777);
+    }
+
+    @Override protected void renderLabels(GuiGraphics graphics, int mouseX, int mouseY) {
+        graphics.drawString(font, playerInventoryTitle, inventoryLabelX, inventoryLabelY, 0x404040, false);
+    }
+
+    @Override public void render(GuiGraphics graphics, int mouseX, int mouseY, float partialTick) {
+        super.render(graphics, mouseX, mouseY, partialTick);
+        renderTooltip(graphics, mouseX, mouseY);
+        if (!menu.book().isEmpty()) {
+            for (int index = 0; index < FLAGS.length; index++) {
+                if (inside(mouseX, mouseY, 5 + (index / 3) * 20, 10 + (index % 3) * 20, 18, 18)) {
+                    Component label = FLAGS[index] == LinkProperties.DISABLE_PLATFORM
+                            ? Component.literal("Generate Platform: "
+                            + (platformEnabled(menu.book().getOrDefault(ModDataComponents.LINK_PROPERTIES.get(),
+                            LinkProperties.NONE)) ? "On" : "Off"))
+                            : LinkProperties.name(FLAGS[index]);
+                    graphics.renderTooltip(font, label, mouseX, mouseY);
+                    return;
+                }
+            }
+        }
+        if (menu.canDelete(minecraft.player)
+                && inside(mouseX, mouseY, menu.awaitingDeletionConfirmation() ? 140 : 120, 32, 18, 18))
+            graphics.renderTooltip(font, Component.translatable(menu.awaitingDeletionConfirmation()
+                    ? "screen.rivencraft.link_modifier.confirm" : "screen.rivencraft.link_modifier.retire"),
+                    mouseX, mouseY);
+    }
+
+    private boolean platformEnabled(LinkProperties properties) {
+        return menu.book().is(ModItems.LINKING_BOOK.get())
+                ? properties.has(LinkProperties.GENERATE_PLATFORM)
+                : !properties.has(LinkProperties.DISABLE_PLATFORM);
+    }
+}

src/main/java/net/dnorberg/rivencraft/client/screen/NotebookScreen.java

@@ -182,9 +182,9 @@ public final class NotebookScreen extends AbstractContainerScreen<NotebookMenu>
 
     private int displayedPageSlots() {
         if (menu.getCarried().is(ModItems.PAGE.get())) {
-            return NotebookMenu.NOTEBOOK_SLOTS;
+            return menu.pageCapacity();
         }
-        for (int index = NotebookMenu.NOTEBOOK_SLOTS - 1; index >= 0; index--) {
+        for (int index = menu.pageCapacity() - 1; index >= 0; index--) {
             if (!menu.getSlot(index).getItem().isEmpty()) {
                 return index + 1;
             }

src/main/java/net/dnorberg/rivencraft/client/screen/WritingDeskScreen.java

@@ -12,6 +12,7 @@ import net.dnorberg.rivencraft.menu.WritingDeskMenu;
 import net.dnorberg.rivencraft.block.entity.WritingDeskBlockEntity;
 import net.dnorberg.rivencraft.registry.ModDataComponents;
 import net.dnorberg.rivencraft.registry.ModItems;
+import net.dnorberg.rivencraft.item.CollationFolderItem;
 import net.dnorberg.rivencraft.writing.NotebookContents;
 import net.dnorberg.rivencraft.writing.SymbolDisplayMetadata;
 import net.minecraft.client.gui.GuiGraphics;
@@ -150,8 +151,8 @@ public final class WritingDeskScreen extends AbstractContainerScreen<WritingDesk
             if (tab == menu.activeCollection() && !allMode) graphics.setColor(0.5F, 0.5F, 1F, 1F);
             graphics.blit(LEGACY_DESK, x, tabY, 0, 166, 58, 37);
             graphics.setColor(1F, 1F, 1F, 1F);
-            // Encode the visible one-based tab number with Legacy's numeric word glyph.
-            SymbolPageTextures.drawNumeral(graphics, tab + 1, x + 8, tabY + 3, 19);
+            // Legacy numbers its Writing Desk collections from zero.
+            SymbolPageTextures.drawNumeral(graphics, tab, x + (tab < 25 ? 8 : 4), tabY + 3, 19);
             ItemStack collection = menu.getSlot(tab).getItem();
             if (!collection.isEmpty()) {
                 String name = collection.getHoverName().getString();
@@ -226,7 +227,7 @@ public final class WritingDeskScreen extends AbstractContainerScreen<WritingDesk
             else if (mouseX < leftPos + 34 && localY >= 29 && localY < 177) {
                 int tab = menu.firstVisibleTab() + (localY - 29) / 37;
                 graphics.renderTooltip(font, Component.translatable("screen.rivencraft.writing_desk.tab_symbol",
-                        tab + 1), mouseX, mouseY);
+                        tab), mouseX, mouseY);
             }
         }
     }
@@ -234,7 +235,7 @@ public final class WritingDeskScreen extends AbstractContainerScreen<WritingDesk
     private List<ItemStack> pages(int collectionIndex) {
         ItemStack collection = menu.getSlot(collectionIndex).getItem();
         if (collection.is(ModItems.PAGE.get())) return List.of(collection);
-        if (collection.is(ModItems.NOTEBOOK.get())) {
+        if (CollationFolderItem.isCollection(collection)) {
             return collection.getOrDefault(ModDataComponents.NOTEBOOK_CONTENTS.get(), NotebookContents.EMPTY).pages();
         }
         return List.of();
@@ -301,9 +302,9 @@ public final class WritingDeskScreen extends AbstractContainerScreen<WritingDesk
 
     private boolean canMovePage(DisplayPage source, DisplayPage target) {
         return !source.stack().isEmpty()
-                && (menu.getSlot(source.collection()).getItem().is(ModItems.NOTEBOOK.get())
+                && (CollationFolderItem.isCollection(menu.getSlot(source.collection()).getItem())
                     || menu.getSlot(source.collection()).getItem().is(ModItems.PAGE.get()))
-                && (menu.getSlot(target.collection()).getItem().is(ModItems.NOTEBOOK.get())
+                && (CollationFolderItem.isCollection(menu.getSlot(target.collection()).getItem())
                     || menu.getSlot(target.collection()).getItem().is(ModItems.PAGE.get()))
                 && (source.collection() != target.collection() || source.index() != target.index());
     }
@@ -317,10 +318,10 @@ public final class WritingDeskScreen extends AbstractContainerScreen<WritingDesk
             if (!slot.mayPlace(held)) return -1;
             ItemStack current = slot.getItem();
             if (current.isEmpty()) return index;
-            if (index < WritingDeskBlockEntity.COLLECTIONS && current.is(ModItems.NOTEBOOK.get())) {
+            if (index < WritingDeskBlockEntity.COLLECTIONS && CollationFolderItem.isCollection(current)) {
                 List<ItemStack> pages = current.getOrDefault(
                         ModDataComponents.NOTEBOOK_CONTENTS.get(), NotebookContents.EMPTY).pages();
-                if (pages.size() < NotebookContents.MAX_PAGES || pages.stream().anyMatch(ItemStack::isEmpty))
+                if (pages.size() < CollationFolderItem.capacity(current) || pages.stream().anyMatch(ItemStack::isEmpty))
                     return index;
             } else if (index > WritingDeskMenu.COPY_RESULT && ItemStack.isSameItemSameComponents(current, held)
                     && current.getCount() < slot.getMaxStackSize(held)) return index;

src/main/java/net/dnorberg/rivencraft/command/RivencraftCommands.java

@@ -112,8 +112,9 @@ public final class RivencraftCommands {
         source.sendSuccess(() -> Component.literal("Rivencraft Ages: " + ages.size()), false);
         for (AgeDefinition age : ages) {
             boolean loaded = source.getServer().getLevel(AgeDimensionService.dimensionKey(age)) != null;
+            boolean retired = AgeRegistrySavedData.get(source.getLevel()).isDead(age.id());
             source.sendSuccess(() -> Component.literal(
-                    (loaded ? "[loaded] " : "[unloaded] ")
+                    (retired ? "[retired] " : loaded ? "[loaded] " : "[unloaded] ")
                             + age.name() + " — " + age.dimensionId()
                             + (age.seasonMode() == null ? "" : " (season: "
                             + age.seasonMode().name().toLowerCase(java.util.Locale.ROOT) + ")")

src/main/java/net/dnorberg/rivencraft/compat/ImmersivePortalsChunkLoaders.java

@@ -16,7 +16,10 @@ import qouteall.q_misc_util.dimension.DimensionIntId;
 
 /** Isolated server bridge; this class is loaded only when Immersive Portals is installed. */
 public final class ImmersivePortalsChunkLoaders {
-    private static final Map<ServerPlayer, ChunkLoader> LOADERS = new IdentityHashMap<>();
+    private static final long MAX_PREVIEW_TICKS = 20L * 60 * 5;
+    private static final Map<ServerPlayer, PreviewLoader> LOADERS = new IdentityHashMap<>();
+
+    private record PreviewLoader(ChunkLoader loader, long expiresAt) {}
 
     private ImmersivePortalsChunkLoaders() {
     }
@@ -35,29 +38,40 @@ public final class ImmersivePortalsChunkLoaders {
 
         ChunkLoader loader = new ChunkLoader(level.dimension(), centerChunkX, centerChunkZ, 8);
         PortalAPI.addChunkLoaderForPlayer(player, loader);
-        LOADERS.put(player, loader);
+        LOADERS.put(player, new PreviewLoader(loader, player.getServer().getTickCount() + MAX_PREVIEW_TICKS));
         ImmPtlChunkTracking.immediatelyUpdateForPlayer(player);
     }
 
     public static synchronized void close(ServerPlayer player) {
-        ChunkLoader loader = LOADERS.remove(player);
-        if (loader != null) {
-            PortalAPI.removeChunkLoaderForPlayer(player, loader);
+        PreviewLoader preview = LOADERS.remove(player);
+        if (preview != null) {
+            PortalAPI.removeChunkLoaderForPlayer(player, preview.loader());
         }
     }
 
+    /** Fail-safe for a lost close packet: no book preview can hold chunks indefinitely. */
+    public static synchronized void expire(MinecraftServer server) {
+        if (server.getTickCount() % 20 != 0) return;
+        LOADERS.entrySet().removeIf(entry -> {
+            if (server.getTickCount() < entry.getValue().expiresAt()
+                    && server.getLevel(entry.getValue().loader().dimension()) != null) return false;
+            PortalAPI.removeChunkLoaderForPlayer(entry.getKey(), entry.getValue().loader());
+            return true;
+        });
+    }
+
     public static synchronized void closeForDimension(ResourceKey<Level> dimension) {
         LOADERS.entrySet().removeIf(entry -> {
-            if (!entry.getValue().dimension().equals(dimension)) {
+            if (!entry.getValue().loader().dimension().equals(dimension)) {
                 return false;
             }
-            PortalAPI.removeChunkLoaderForPlayer(entry.getKey(), entry.getValue());
+            PortalAPI.removeChunkLoaderForPlayer(entry.getKey(), entry.getValue().loader());
             return true;
         });
     }
 
     public static synchronized void closeAll() {
-        LOADERS.forEach(PortalAPI::removeChunkLoaderForPlayer);
+        LOADERS.forEach((player, preview) -> PortalAPI.removeChunkLoaderForPlayer(player, preview.loader()));
         LOADERS.clear();
     }
 

src/main/java/net/dnorberg/rivencraft/compat/ImmersivePortalsCrystalView.java

@@ -23,12 +23,12 @@ public final class ImmersivePortalsCrystalView {
     private ImmersivePortalsCrystalView() {}
 
     public static void activate(ServerLevel source, BlockPos receptacle,
-                                CrystalPortalNetwork.Plan plan, LinkTarget target) {
+                                CrystalPortalNetwork.Plan plan, LinkTarget target, boolean requireFooting) {
         remove(source, receptacle);
         ServerLevel destinationLevel = source.getServer().getLevel(target.location().dimension());
         if (destinationLevel == null) return;
         // This is the same safe-location search used by portal book travel.
-        var arrival = LinkingService.resolveDestination(destinationLevel, target.location().pos(), false);
+        var arrival = LinkingService.resolveDestination(destinationLevel, target.location().pos(), requireFooting);
         if (arrival.isEmpty()) return;
         Vec3 arrivalEye = arrival.get().add(0, 1.62, 0);
         for (CrystalPortalSurfaces.Surface surface : CrystalPortalSurfaces.group(source, plan)) {
@@ -46,11 +46,15 @@ public final class ImmersivePortalsCrystalView {
                         && (entity.portalTag.equals(tag) || entity.portalTag.equals(oldTag)))) portal.discard();
     }
 
-    public static boolean exists(ServerLevel source, BlockPos receptacle) {
+    public static boolean complete(ServerLevel source, BlockPos receptacle,
+                                   CrystalPortalNetwork.Plan plan, LinkTarget target) {
         String tag = tag(receptacle);
-        return !source.getEntitiesOfClass(Portal.class,
+        var views = source.getEntitiesOfClass(Portal.class,
                 new AABB(receptacle).inflate(CrystalPortalNetwork.MAX_RADIUS + 2),
-                entity -> tag.equals(entity.portalTag)).isEmpty();
+                entity -> tag.equals(entity.portalTag));
+        int expected = CrystalPortalSurfaces.group(source, plan).size() * 2;
+        return expected > 0 && views.size() == expected && views.stream()
+                .allMatch(view -> target.location().dimension().equals(view.getDestDim()));
     }
 
     private static void spawn(ServerLevel source, BlockPos receptacle, CrystalPortalSurfaces.Surface surface,

src/main/java/net/dnorberg/rivencraft/compat/RivencraftPonderGuide.java

@@ -0,0 +1,108 @@
+package net.dnorberg.rivencraft.compat;
+
+import net.createmod.ponder.api.PonderPalette;
+import net.createmod.ponder.api.registration.PonderPlugin;
+import net.createmod.ponder.api.registration.PonderSceneRegistrationHelper;
+import net.createmod.ponder.api.scene.SceneBuilder;
+import net.createmod.ponder.api.scene.SceneBuildingUtil;
+import net.createmod.ponder.foundation.PonderIndex;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.block.BookReceptacleBlock;
+import net.dnorberg.rivencraft.block.CrystalPortalBlock;
+import net.dnorberg.rivencraft.registry.ModBlocks;
+import net.dnorberg.rivencraft.registry.ModItems;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Direction;
+import net.minecraft.resources.ResourceLocation;
+import net.minecraft.world.entity.EntityType;
+import net.minecraft.world.item.ItemStack;
+import net.minecraft.world.level.block.Blocks;
+
+/** Create-only Ponder registration; this class is never loaded without Create. */
+public final class RivencraftPonderGuide implements PonderPlugin {
+    private static final ResourceLocation DEPOT_TEMPLATE = ResourceLocation.fromNamespaceAndPath("create", "depot");
+
+    private RivencraftPonderGuide() {}
+
+    public static void register() {
+        PonderIndex.addPlugin(new RivencraftPonderGuide());
+    }
+
+    @Override
+    public String getModId() {
+        return Rivencraft.MOD_ID;
+    }
+
+    @Override
+    public void registerScenes(PonderSceneRegistrationHelper<ResourceLocation> helper) {
+        // Create is already present when this plugin is registered. Its small
+        // depot schematic supplies an emptyable 6×4×6 canvas, so Rivencraft
+        // does not need to ship a separate binary Ponder template.
+        helper.forComponents(ModItems.BOOK_RECEPTACLE.getId(), ModItems.CRYSTAL_BLOCK.getId())
+                .addStoryBoard(DEPOT_TEMPLATE, RivencraftPonderGuide::crystalPortal);
+    }
+
+    private static void crystalPortal(SceneBuilder scene, SceneBuildingUtil util) {
+        scene.title("crystal_portal", "Building a Crystal Portal");
+        scene.configureBasePlate(0, 0, 6);
+        scene.scaleSceneView(0.85F);
+        scene.showBasePlate();
+        scene.world().setBlocks(util.select().fromTo(0, 1, 0, 5, 3, 5),
+                Blocks.AIR.defaultBlockState(), false);
+        scene.idle(10);
+
+        BlockPos center = util.grid().at(3, 2, 3);
+        scene.overlay().showText(65).text("Build a closed crystal frame with an open center.")
+                .pointAt(util.vector().centerOf(center)).placeNearTarget();
+        for (int x = 2; x <= 4; x++) {
+            for (int y = 1; y <= 3; y++) {
+                if (x == 3 && y == 2) continue;
+                BlockPos pos = util.grid().at(x, y, 3);
+                scene.world().setBlock(pos, ModBlocks.CRYSTAL_BLOCK.get().defaultBlockState(), false);
+                scene.world().showSection(util.select().position(pos), Direction.DOWN);
+                scene.idle(3);
+            }
+        }
+        scene.idle(30);
+
+        BlockPos receptacle = util.grid().at(2, 1, 2);
+        scene.overlay().showText(70).text("Attach a Book Receptacle to one crystal, facing outward.")
+                .pointAt(util.vector().centerOf(receptacle)).placeNearTarget();
+        scene.world().setBlock(receptacle, ModBlocks.BOOK_RECEPTACLE.get().defaultBlockState()
+                .setValue(BookReceptacleBlock.FACING, Direction.NORTH), false);
+        scene.world().showSection(util.select().position(receptacle), Direction.DOWN);
+        scene.idle(75);
+
+        scene.overlay().showText(65).text("Insert a bound Linking or Descriptive Book to activate the portal.")
+                .colored(PonderPalette.INPUT).pointAt(util.vector().centerOf(receptacle)).placeNearTarget();
+        scene.overlay().showControls(util.vector().centerOf(receptacle),
+                net.createmod.catnip.math.Pointing.RIGHT, 55)
+                .rightClick().withItem(new ItemStack(ModItems.LINKING_BOOK.get()));
+        scene.idle(65);
+
+        scene.world().setBlock(center, ModBlocks.CRYSTAL_PORTAL.get().defaultBlockState()
+                .setValue(CrystalPortalBlock.AXIS, Direction.Axis.Z), false);
+        scene.world().showSection(util.select().position(center), Direction.DOWN);
+        scene.effects().indicateSuccess(center);
+        scene.overlay().showText(80).text("Step through the portal. Remove the book to close it.")
+                .colored(PonderPalette.OUTPUT).pointAt(util.vector().centerOf(center)).placeNearTarget();
+        scene.idle(20);
+        var parrot = scene.world().createEntity(world -> {
+            var bird = EntityType.PARROT.create(world);
+            bird.setNoAi(true);
+            bird.setPos(3.5, 2.05, 1.5);
+            bird.setYRot(0);
+            return bird;
+        });
+        scene.idle(10);
+        for (int step = 1; step <= 7; step++) {
+            double z = 1.5 + step * 0.42;
+            scene.world().modifyEntity(parrot, bird -> bird.setPos(3.5, 2.05, z));
+            scene.idle(5);
+        }
+        scene.world().modifyEntity(parrot, bird -> bird.discard());
+        scene.effects().indicateSuccess(center);
+        scene.idle(20);
+        scene.markAsFinished();
+    }
+}

src/main/java/net/dnorberg/rivencraft/compat/jei/RivencraftJeiPlugin.java

@@ -25,12 +25,14 @@ import net.dnorberg.rivencraft.Rivencraft;
 import net.dnorberg.rivencraft.item.PageItem;
 import net.dnorberg.rivencraft.book.LinkProperties;
 import net.dnorberg.rivencraft.registry.ModDataComponents;
+import net.dnorberg.rivencraft.registry.ModCreativeTabs;
 import net.dnorberg.rivencraft.writing.InkModifierIngredients;
 import net.dnorberg.rivencraft.writing.PageContent;
 import net.dnorberg.rivencraft.writing.SymbolReference;
 import net.dnorberg.rivencraft.registry.ModItems;
 import net.minecraft.client.Minecraft;
 import net.minecraft.client.gui.GuiGraphics;
+import net.minecraft.core.component.DataComponents;
 import net.minecraft.network.chat.Component;
 import net.minecraft.network.chat.MutableComponent;
 import net.minecraft.resources.ResourceLocation;
@@ -63,6 +65,11 @@ public final class RivencraftJeiPlugin implements IModPlugin {
                         case UNRESOLVED_SYMBOL -> "unresolved:" + content.symbol().orElseThrow().id();
                     };
                 });
+        registration.registerSubtypeInterpreter(ModItems.SYMBOL_PORTFOLIO.get(),
+                (IIngredientSubtypeInterpreter<ItemStack>) (stack, context) -> {
+                    Component name = stack.get(DataComponents.CUSTOM_NAME);
+                    return name == null ? "empty" : name.getString();
+                });
     }
 
     @Override
@@ -72,6 +79,7 @@ public final class RivencraftJeiPlugin implements IModPlugin {
         var connection = Minecraft.getInstance().getConnection();
         if (connection != null) {
             pages.addAll(PageItem.creativeSymbolPages(connection.registryAccess()));
+            pages.addAll(ModCreativeTabs.creativeSymbolPortfolios(connection.registryAccess()));
         } else {
             PageItem.bundledCreativeSymbols().stream().map(PageItem::createBundledCreativePage)
                     .forEach(pages::add);
@@ -84,6 +92,8 @@ public final class RivencraftJeiPlugin implements IModPlugin {
         // JEI discovers the base Page item as a blank stack; only authored pages belong in its list.
         runtime.getIngredientVisibility().hideIngredients(VanillaTypes.ITEM_STACK,
                 List.of(new ItemStack(ModItems.PAGE.get())), List.of(UidContext.Ingredient));
+        runtime.getIngredientVisibility().hideIngredients(VanillaTypes.ITEM_STACK,
+                List.of(new ItemStack(ModItems.SYMBOL_PORTFOLIO.get())), List.of(UidContext.Ingredient));
         var connection = Minecraft.getInstance().getConnection();
         if (connection == null) return;
         Set<ResourceLocation> known = runtime.getIngredientManager().getAllItemStacks().stream()
@@ -98,6 +108,19 @@ public final class RivencraftJeiPlugin implements IModPlugin {
         if (!missing.isEmpty()) {
             runtime.getIngredientManager().addIngredientsAtRuntime(VanillaTypes.ITEM_STACK, missing);
         }
+        Set<String> knownPortfolios = runtime.getIngredientManager().getAllItemStacks().stream()
+                .filter(stack -> stack.is(ModItems.SYMBOL_PORTFOLIO.get()))
+                .map(stack -> stack.get(DataComponents.CUSTOM_NAME))
+                .filter(java.util.Objects::nonNull)
+                .map(Component::getString)
+                .collect(Collectors.toSet());
+        List<ItemStack> missingPortfolios = ModCreativeTabs.creativeSymbolPortfolios(connection.registryAccess())
+                .stream()
+                .filter(stack -> !knownPortfolios.contains(stack.getHoverName().getString()))
+                .toList();
+        if (!missingPortfolios.isEmpty()) {
+            runtime.getIngredientManager().addIngredientsAtRuntime(VanillaTypes.ITEM_STACK, missingPortfolios);
+        }
     }
 
     @Override

src/main/java/net/dnorberg/rivencraft/config/RivencraftConfig.java

@@ -75,7 +75,7 @@ public final class RivencraftConfig {
                         "Controls automatic Return Link creation for Descriptive Book travel.",
                         "ON_CREATION creates one link when an Age is first reached; ALWAYS creates one on every arrival; DISABLED creates none."
                 )
-                .defineEnum("return_link_mode", ReturnLinkMode.ON_CREATION);
+                .defineEnum("return_link_mode", ReturnLinkMode.DISABLED);
         builder.pop();
         builder.push("libraries");
         LIBRARY_LOOT_MODE = builder.comment(

src/main/java/net/dnorberg/rivencraft/entity/DroppedBookEntity.java

@@ -0,0 +1,62 @@
+package net.dnorberg.rivencraft.entity;
+
+import net.dnorberg.rivencraft.registry.ModEntities;
+import net.minecraft.nbt.CompoundTag;
+import net.minecraft.world.entity.EntityType;
+import net.minecraft.world.entity.item.ItemEntity;
+import net.minecraft.world.item.ItemStack;
+import net.minecraft.world.level.Level;
+import net.minecraft.world.phys.Vec3;
+
+/** A recoverable, model-rendered book left behind by handheld linking. */
+public final class DroppedBookEntity extends ItemEntity {
+    private static final String DECAY_TICKS_TAG = "BookDecayTicks";
+    private static final int SLOW_DECAY_INTERVAL = 10_000;
+    private int decayTicks;
+
+    public DroppedBookEntity(EntityType<DroppedBookEntity> type, Level level) {
+        super(type, level);
+    }
+
+    public DroppedBookEntity(Level level, Vec3 position, ItemStack stack) {
+        this(ModEntities.DROPPED_BOOK.get(), level);
+        setPos(position.x, position.y + 0.25, position.z);
+        setDeltaMovement(Vec3.ZERO);
+        setItem(stack);
+        setUnlimitedLifetime();
+        setPickUpDelay(20);
+    }
+
+    /** Vanilla's pickup particle calls ItemEntity.copy() and renders the returned entity. */
+    @Override
+    public DroppedBookEntity copy() {
+        DroppedBookEntity copy = new DroppedBookEntity(ModEntities.DROPPED_BOOK.get(), level());
+        copy.copyPosition(this);
+        copy.setItem(getItem().copy());
+        copy.setUnlimitedLifetime();
+        return copy;
+    }
+
+    @Override
+    public void tick() {
+        super.tick();
+        if (level().isClientSide || isRemoved()) return;
+        if (++decayTicks >= SLOW_DECAY_INTERVAL) {
+            decayTicks = 0;
+            hurt(damageSources().starve(), 1.0F);
+        }
+        if (!isRemoved() && isInWaterOrRain()) hurt(damageSources().drown(), 1.0F);
+    }
+
+    @Override
+    public void addAdditionalSaveData(CompoundTag tag) {
+        super.addAdditionalSaveData(tag);
+        tag.putInt(DECAY_TICKS_TAG, decayTicks);
+    }
+
+    @Override
+    public void readAdditionalSaveData(CompoundTag tag) {
+        super.readAdditionalSaveData(tag);
+        decayTicks = Math.max(0, Math.min(tag.getInt(DECAY_TICKS_TAG), SLOW_DECAY_INTERVAL - 1));
+    }
+}

src/main/java/net/dnorberg/rivencraft/event/AgeCelestialAngleSync.java

@@ -3,11 +3,11 @@ package net.dnorberg.rivencraft.event;
 import net.dnorberg.rivencraft.book.AgeDefinition;
 import net.dnorberg.rivencraft.book.AgeDimensionService;
 import net.dnorberg.rivencraft.book.AgeRegistrySavedData;
+import net.dnorberg.rivencraft.book.AgeSkyProfile;
 import net.dnorberg.rivencraft.network.AgeCelestialAnglePayload;
 import net.minecraft.server.level.ServerPlayer;
 import net.neoforged.neoforge.event.entity.player.PlayerEvent;
 import net.neoforged.neoforge.network.PacketDistributor;
-import net.neoforged.neoforge.network.registration.NetworkRegistry;
 
 /** Sends saved celestial angles when a client joins or enters an Age. */
 public final class AgeCelestialAngleSync {
@@ -34,10 +34,8 @@ public final class AgeCelestialAngleSync {
     }
 
     public static void send(ServerPlayer player, AgeDefinition age) {
-        if (!NetworkRegistry.hasChannel(player.connection, AgeCelestialAnglePayload.TYPE.id())) {
-            return;
-        }
         PacketDistributor.sendToPlayer(player, new AgeCelestialAnglePayload(
-                AgeDimensionService.dimensionKey(age), age.traits().celestialAngle()));
+                AgeDimensionService.dimensionKey(age), age.traits().celestialAngle(),
+                AgeSkyProfile.forAge(age)));
     }
 }

src/main/java/net/dnorberg/rivencraft/event/AgeLifecycleEvents.java

@@ -1,10 +1,13 @@
 package net.dnorberg.rivencraft.event;
 
 import net.dnorberg.rivencraft.compat.ImmersivePortalsChunkLoaders;
+import net.dnorberg.rivencraft.portal.PortalTravelCooldown;
+import net.dnorberg.rivencraft.portal.PortalTravelQueue;
 import net.minecraft.server.level.ServerPlayer;
 import net.neoforged.fml.ModList;
 import net.neoforged.neoforge.event.entity.player.PlayerEvent;
 import net.neoforged.neoforge.event.server.ServerStoppingEvent;
+import net.neoforged.neoforge.event.tick.ServerTickEvent;
 
 /** Server-authoritative cleanup for resources that exist only while a preview is active. */
 public final class AgeLifecycleEvents {
@@ -12,6 +15,10 @@ public final class AgeLifecycleEvents {
     }
 
     public static void onPlayerLoggedOut(PlayerEvent.PlayerLoggedOutEvent event) {
+        if (event.getEntity() instanceof ServerPlayer player) {
+            PortalTravelCooldown.forget(player);
+            PortalTravelQueue.forget(player);
+        }
         if (event.getEntity() instanceof ServerPlayer player
                 && ModList.get().isLoaded("immersive_portals_core")) {
             ImmersivePortalsChunkLoaders.close(player);
@@ -19,8 +26,16 @@ public final class AgeLifecycleEvents {
     }
 
     public static void onServerStopping(ServerStoppingEvent event) {
+        PortalTravelCooldown.clear();
+        PortalTravelQueue.clear();
         if (ModList.get().isLoaded("immersive_portals_core")) {
             ImmersivePortalsChunkLoaders.closeAll();
         }
     }
+
+    public static void onServerTickPost(ServerTickEvent.Post event) {
+        PortalTravelQueue.process(event.getServer());
+        if (ModList.get().isLoaded("immersive_portals_core"))
+            ImmersivePortalsChunkLoaders.expire(event.getServer());
+    }
 }

src/main/java/net/dnorberg/rivencraft/gametest/CrystalPortalGameTests.java

@@ -6,6 +6,9 @@ import net.dnorberg.rivencraft.block.CrystalPortalBlock;
 import net.dnorberg.rivencraft.block.entity.BookReceptacleBlockEntity;
 import net.dnorberg.rivencraft.block.entity.CrystalPortalBlockEntity;
 import net.dnorberg.rivencraft.book.LinkTarget;
+import net.dnorberg.rivencraft.book.LinkProperties;
+import net.dnorberg.rivencraft.book.LinkingService;
+import net.dnorberg.rivencraft.registry.ModDataComponents;
 import net.dnorberg.rivencraft.portal.CrystalPortalNetwork;
 import net.dnorberg.rivencraft.portal.CrystalPortalSurfaces;
 import net.dnorberg.rivencraft.portal.PortalTravelCooldown;
@@ -16,7 +19,14 @@ import net.minecraft.core.Direction;
 import net.minecraft.core.GlobalPos;
 import net.minecraft.gametest.framework.GameTest;
 import net.minecraft.gametest.framework.GameTestHelper;
+import net.minecraft.nbt.CompoundTag;
+import net.minecraft.server.level.ServerLevel;
 import net.minecraft.world.item.ItemStack;
+import net.minecraft.world.InteractionHand;
+import net.minecraft.world.item.context.BlockPlaceContext;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.phys.BlockHitResult;
+import net.minecraft.world.phys.Vec3;
 import net.neoforged.neoforge.gametest.GameTestHolder;
 import net.neoforged.neoforge.gametest.PrefixGameTestTemplate;
 
@@ -29,14 +39,17 @@ public final class CrystalPortalGameTests {
     public static void completeFrameActivatesAndReleasesBook(GameTestHelper helper) {
         var level = helper.getLevel();
         for (int x = 0; x < 3; x++) for (int y = 1; y < 4; y++) {
-            if (x == 1 && y == 2) continue;
+            if (x == 1 && y == 2) {
+                level.setBlock(helper.absolutePos(new BlockPos(x, y, 1)), Blocks.AIR.defaultBlockState(), 3);
+                continue;
+            }
             level.setBlock(helper.absolutePos(new BlockPos(x, y, 1)),
                     ModBlocks.CRYSTAL_BLOCK.get().defaultBlockState(), 3);
         }
         BlockPos holderPos = helper.absolutePos(new BlockPos(0, 1, 0));
         level.setBlock(holderPos, ModBlocks.BOOK_RECEPTACLE.get().defaultBlockState()
                 .setValue(BookReceptacleBlock.FACING, Direction.NORTH), 3);
-        CrystalPortalNetwork.Plan plan = CrystalPortalNetwork.plan(level, holderPos);
+        CrystalPortalNetwork.Plan plan = planLoaded(level, holderPos);
         helper.assertTrue(plan.valid(), "A closed crystal frame must form a portal");
         BookReceptacleBlockEntity holder = (BookReceptacleBlockEntity) level.getBlockEntity(holderPos);
         holder.setBook(new ItemStack(ModItems.LINKING_BOOK.get()));
@@ -44,12 +57,34 @@ public final class CrystalPortalGameTests {
         holder.setDestination(destination);
         BookReceptacleBlockEntity restored = new BookReceptacleBlockEntity(holderPos, holder.getBlockState());
         restored.loadWithComponents(holder.saveWithoutMetadata(level.registryAccess()), level.registryAccess());
+        helper.assertTrue(restored.getBook().is(ModItems.LINKING_BOOK.get()),
+                "The book itself must survive a save/reload cycle");
         helper.assertValueEqual(restored.destination(), destination,
                 "The portal destination must survive a save/reload cycle");
         helper.assertTrue(CrystalPortalNetwork.activate(level, holderPos, plan), "Portal placement must succeed");
         BlockPos center = helper.absolutePos(new BlockPos(1, 2, 1));
         helper.assertTrue(level.getBlockEntity(center) instanceof CrystalPortalBlockEntity portal
                 && holderPos.equals(portal.receptacle()), "The portal must point to its one book holder");
+        CrystalPortalBlockEntity savedPortal = (CrystalPortalBlockEntity) level.getBlockEntity(center);
+        CrystalPortalBlockEntity restoredPortal = new CrystalPortalBlockEntity(center, savedPortal.getBlockState());
+        CompoundTag savedPortalTag = savedPortal.saveWithoutMetadata(level.registryAccess());
+        helper.assertTrue(savedPortalTag.contains("Receptacle"), "Portal owner must serialize: " + savedPortalTag);
+        restoredPortal.loadWithComponents(savedPortalTag,
+                level.registryAccess());
+        helper.assertTrue(restoredPortal.receptacle() != null, "Portal owner must deserialize: " + savedPortalTag);
+        helper.assertValueEqual(restoredPortal.receptacle(), holderPos,
+                "The portal-to-receptacle pointer must survive a full chunk save");
+        helper.assertTrue(CrystalPortalNetwork.reconcile(level, holderPos),
+                "A saved portal must recover without duplicating cells");
+        CrystalPortalNetwork.setLiveView(level, plan, true);
+        CrystalPortalBlockEntity livePortal = (CrystalPortalBlockEntity) level.getBlockEntity(center);
+        helper.assertValueEqual(livePortal.receptacle(), holderPos,
+                "Switching to the live view must retain the portal's book holder");
+        helper.assertTrue(livePortal.saveWithoutMetadata(level.registryAccess()).contains("Receptacle"),
+                "The live-view portal must persist its holder pointer to disk");
+        CrystalPortalNetwork.setLiveView(level, plan, false);
+        helper.assertValueEqual(((CrystalPortalBlockEntity) level.getBlockEntity(center)).receptacle(), holderPos,
+                "Switching back to the fallback texture must retain the holder");
         helper.assertValueEqual(level.getBlockState(center).getValue(CrystalPortalBlock.AXIS), Direction.Axis.Z,
                 "A north/south opening must only show its two player-facing sides");
         CrystalPortalNetwork.shutdown(level, holderPos);
@@ -57,6 +92,33 @@ public final class CrystalPortalGameTests {
         helper.succeed();
     }
 
+    @GameTest(template = "empty")
+    public static void backgroundRepairDoesNotRecreateMissingCells(GameTestHelper helper) {
+        var level = helper.getLevel();
+        for (int x = 0; x < 3; x++) for (int y = 1; y < 4; y++) {
+            if (x == 1 && y == 2) {
+                level.setBlock(helper.absolutePos(new BlockPos(x, y, 1)), Blocks.AIR.defaultBlockState(), 3);
+                continue;
+            }
+            level.setBlock(helper.absolutePos(new BlockPos(x, y, 1)),
+                    ModBlocks.CRYSTAL_BLOCK.get().defaultBlockState(), 3);
+        }
+        BlockPos holderPos = helper.absolutePos(new BlockPos(0, 1, 0));
+        level.setBlock(holderPos, ModBlocks.BOOK_RECEPTACLE.get().defaultBlockState()
+                .setValue(BookReceptacleBlock.FACING, Direction.NORTH), 3);
+        BookReceptacleBlockEntity holder = (BookReceptacleBlockEntity) level.getBlockEntity(holderPos);
+        holder.setBook(new ItemStack(ModItems.LINKING_BOOK.get()));
+        helper.assertTrue(CrystalPortalNetwork.activate(level, holderPos, planLoaded(level, holderPos)),
+                "Portal must activate before the repair check");
+        BlockPos center = helper.absolutePos(new BlockPos(1, 2, 1));
+        level.removeBlock(center, false);
+        helper.assertTrue(!CrystalPortalNetwork.reconcile(level, holderPos),
+                "An unattended repair must not place a new cell across a protection boundary");
+        helper.assertTrue(level.getBlockState(center).isAir() && !holder.getBook().isEmpty(),
+                "A broken portal stays shut down while its one stored book remains retrievable");
+        helper.succeed();
+    }
+
     private static BlockPos centerTarget(GameTestHelper helper) {
         return helper.absolutePos(new BlockPos(1, 2, 1));
     }
@@ -65,7 +127,10 @@ public final class CrystalPortalGameTests {
     public static void eastWestOpeningOrientsFallbackSurface(GameTestHelper helper) {
         var level = helper.getLevel();
         for (int z = 1; z <= 3; z++) for (int y = 1; y <= 3; y++) {
-            if (z == 2 && y == 2) continue;
+            if (z == 2 && y == 2) {
+                level.setBlock(helper.absolutePos(new BlockPos(1, y, z)), Blocks.AIR.defaultBlockState(), 3);
+                continue;
+            }
             level.setBlock(helper.absolutePos(new BlockPos(1, y, z)),
                     ModBlocks.CRYSTAL_BLOCK.get().defaultBlockState(), 3);
         }
@@ -74,7 +139,7 @@ public final class CrystalPortalGameTests {
                 .setValue(BookReceptacleBlock.FACING, Direction.NORTH), 3);
         ((BookReceptacleBlockEntity) level.getBlockEntity(holderPos))
                 .setBook(new ItemStack(ModItems.LINKING_BOOK.get()));
-        helper.assertTrue(CrystalPortalNetwork.activate(level, holderPos, CrystalPortalNetwork.plan(level, holderPos)),
+        helper.assertTrue(CrystalPortalNetwork.activate(level, holderPos, planLoaded(level, holderPos)),
                 "The east/west crystal opening must activate");
         helper.assertValueEqual(level.getBlockState(helper.absolutePos(new BlockPos(1, 2, 2)))
                 .getValue(CrystalPortalBlock.AXIS), Direction.Axis.X,
@@ -86,20 +151,64 @@ public final class CrystalPortalGameTests {
     public static void horizontalOpeningOrientsFallbackSurface(GameTestHelper helper) {
         var level = helper.getLevel();
         for (int x = 0; x < 3; x++) for (int z = 0; z < 3; z++) {
-            if (x == 1 && z == 1) continue;
+            if (x == 1 && z == 1) {
+                level.setBlock(helper.absolutePos(new BlockPos(x, 1, z)), Blocks.AIR.defaultBlockState(), 3);
+                continue;
+            }
             level.setBlock(helper.absolutePos(new BlockPos(x, 1, z)),
                     ModBlocks.CRYSTAL_BLOCK.get().defaultBlockState(), 3);
         }
         BlockPos holderPos = helper.absolutePos(new BlockPos(0, 2, 1));
         level.setBlock(holderPos, ModBlocks.BOOK_RECEPTACLE.get().defaultBlockState()
                 .setValue(BookReceptacleBlock.FACING, Direction.UP), 3);
-        ((BookReceptacleBlockEntity) level.getBlockEntity(holderPos))
-                .setBook(new ItemStack(ModItems.LINKING_BOOK.get()));
-        helper.assertTrue(CrystalPortalNetwork.activate(level, holderPos, CrystalPortalNetwork.plan(level, holderPos)),
+        LinkTarget destination = new LinkTarget(GlobalPos.of(level.dimension(), centerTarget(helper)), 0, 0);
+        ItemStack book = new ItemStack(ModItems.LINKING_BOOK.get());
+        book.set(ModDataComponents.LINK_TARGET.get(), destination);
+        BookReceptacleBlockEntity holder = (BookReceptacleBlockEntity) level.getBlockEntity(holderPos);
+        holder.setBook(book);
+        holder.setDestination(destination);
+        helper.assertTrue(CrystalPortalNetwork.activate(level, holderPos, planLoaded(level, holderPos)),
                 "The horizontal crystal opening must activate");
         helper.assertValueEqual(level.getBlockState(helper.absolutePos(new BlockPos(1, 1, 1)))
                 .getValue(CrystalPortalBlock.AXIS), Direction.Axis.Y,
                 "The fallback surface must face up and down");
+        helper.assertValueEqual(CrystalPortalSurfaces.group(level, planLoaded(level, holderPos)).getFirst().normal(),
+                Direction.UP, "The horizontal opening must provide an upward-facing destination view");
+        var player = helper.makeMockServerPlayerInLevel();
+        helper.assertValueEqual(LinkingService.travelPortal(player, destination, LinkProperties.NONE),
+                LinkingService.LinkResult.INTRA_LINKING_REQUIRED,
+                "A normal book may show a portal but must not link within its own dimension");
+        helper.assertTrue(level.getBlockState(helper.absolutePos(new BlockPos(1, 1, 1)))
+                        .is(ModBlocks.CRYSTAL_PORTAL.get()) && !holder.getBook().isEmpty(),
+                "Rejected intra-link travel must leave the visual portal and its book intact");
+        helper.succeed();
+    }
+
+    @GameTest(template = "empty")
+    public static void undersideReceptaclePlacesAndActivatesHorizontalFrame(GameTestHelper helper) {
+        var level = helper.getLevel();
+        for (int x = 0; x < 3; x++) for (int z = 0; z < 3; z++) {
+            level.setBlock(helper.absolutePos(new BlockPos(x, 2, z)),
+                    x == 1 && z == 1 ? Blocks.AIR.defaultBlockState()
+                            : ModBlocks.CRYSTAL_BLOCK.get().defaultBlockState(), 3);
+        }
+        BlockPos support = helper.absolutePos(new BlockPos(0, 2, 1));
+        BlockPos holderPos = support.below();
+        BlockPlaceContext context = new BlockPlaceContext(level, null, InteractionHand.MAIN_HAND,
+                new ItemStack(ModItems.BOOK_RECEPTACLE.get()),
+                new BlockHitResult(Vec3.atCenterOf(support).add(0, -0.5, 0),
+                        Direction.DOWN, support, false));
+        var placed = ModBlocks.BOOK_RECEPTACLE.get().getStateForPlacement(context);
+        helper.assertTrue(placed != null && placed.getValue(BookReceptacleBlock.FACING) == Direction.DOWN,
+                "Clicking the underside of a Crystal Block must place a downward-facing receptacle");
+        level.setBlock(holderPos, placed, 3);
+        ((BookReceptacleBlockEntity) level.getBlockEntity(holderPos))
+                .setBook(new ItemStack(ModItems.LINKING_BOOK.get()));
+        helper.assertTrue(CrystalPortalNetwork.activate(level, holderPos, planLoaded(level, holderPos)),
+                "A ceiling-mounted receptacle must activate its horizontal crystal frame");
+        helper.assertValueEqual(level.getBlockState(helper.absolutePos(new BlockPos(1, 2, 1)))
+                .getValue(CrystalPortalBlock.AXIS), Direction.Axis.Y,
+                "The underside-mounted portal surface remains horizontal");
         helper.succeed();
     }
 
@@ -111,7 +220,7 @@ public final class CrystalPortalGameTests {
                 ModBlocks.CRYSTAL_BLOCK.get().defaultBlockState(), 3);
         level.setBlock(holderPos, ModBlocks.BOOK_RECEPTACLE.get().defaultBlockState()
                 .setValue(BookReceptacleBlock.FACING, Direction.NORTH), 3);
-        helper.assertTrue(!CrystalPortalNetwork.plan(level, holderPos).valid(),
+        helper.assertTrue(!planLoaded(level, holderPos).valid(),
                 "An incomplete frame must not take a book or leave portal cells");
         helper.succeed();
     }
@@ -120,28 +229,89 @@ public final class CrystalPortalGameTests {
     public static void multiCellOpeningHasOneContinuousView(GameTestHelper helper) {
         var level = helper.getLevel();
         for (int x = 0; x < 3; x++) for (int y = 1; y < 5; y++) {
-            if (x == 1 && (y == 2 || y == 3)) continue;
+            if (x == 1 && (y == 2 || y == 3)) {
+                level.setBlock(helper.absolutePos(new BlockPos(x, y, 1)), Blocks.AIR.defaultBlockState(), 3);
+                continue;
+            }
             level.setBlock(helper.absolutePos(new BlockPos(x, y, 1)),
                     ModBlocks.CRYSTAL_BLOCK.get().defaultBlockState(), 3);
         }
         BlockPos holderPos = helper.absolutePos(new BlockPos(0, 1, 0));
         level.setBlock(holderPos, ModBlocks.BOOK_RECEPTACLE.get().defaultBlockState()
                 .setValue(BookReceptacleBlock.FACING, Direction.NORTH), 3);
-        CrystalPortalNetwork.Plan plan = CrystalPortalNetwork.plan(level, holderPos);
+        CrystalPortalNetwork.Plan plan = planLoaded(level, holderPos);
         helper.assertValueEqual(plan.portalCells().size(), 2, "The opening contains two portal cells");
+        ((BookReceptacleBlockEntity) level.getBlockEntity(holderPos))
+                .setBook(new ItemStack(ModItems.LINKING_BOOK.get()));
+        helper.assertTrue(CrystalPortalNetwork.activate(level, holderPos, plan),
+                "The two-cell opening must activate before its live-view grouping is inspected");
         helper.assertValueEqual(CrystalPortalSurfaces.group(level, plan).size(), 1,
                 "Both cells must share one coherent Immersive Portals view");
         helper.succeed();
     }
 
     @GameTest(template = "empty")
-    public static void savedCooldownFromPreviousServerCannotBlockPortal(GameTestHelper helper) {
-        helper.assertTrue(!PortalTravelCooldown.blocked(5, -1),
-                "A player with no prior portal use must link immediately");
-        helper.assertTrue(!PortalTravelCooldown.blocked(5, 12000),
-                "A saved tick from the previous server session must not block travel");
-        helper.assertTrue(PortalTravelCooldown.blocked(105, 100),
-                "A recent portal use in the current session must still prevent loops");
+    public static void largeOpeningSurvivesAtomicActivation(GameTestHelper helper) {
+        var level = helper.getLevel();
+        for (int x = 0; x < 5; x++) for (int y = 1; y < 6; y++) {
+            if (x > 0 && x < 4 && y > 1 && y < 5) {
+                level.setBlock(helper.absolutePos(new BlockPos(x, y, 1)), Blocks.AIR.defaultBlockState(), 3);
+                continue;
+            }
+            level.setBlock(helper.absolutePos(new BlockPos(x, y, 1)),
+                    ModBlocks.CRYSTAL_BLOCK.get().defaultBlockState(), 3);
+        }
+        BlockPos holderPos = helper.absolutePos(new BlockPos(0, 1, 0));
+        level.setBlock(holderPos, ModBlocks.BOOK_RECEPTACLE.get().defaultBlockState()
+                .setValue(BookReceptacleBlock.FACING, Direction.NORTH), 3);
+        BookReceptacleBlockEntity holder = (BookReceptacleBlockEntity) level.getBlockEntity(holderPos);
+        holder.setBook(new ItemStack(ModItems.LINKING_BOOK.get()));
+        CrystalPortalNetwork.Plan plan = planLoaded(level, holderPos);
+        helper.assertValueEqual(plan.portalCells().size(), 9, "The large frame has a 3×3 opening");
+        helper.assertTrue(CrystalPortalNetwork.activate(level, holderPos, plan),
+                "The complete opening must activate");
+        for (BlockPos pos : plan.portalCells()) {
+            helper.assertTrue(level.getBlockState(pos).is(ModBlocks.CRYSTAL_PORTAL.get())
+                    && level.getBlockEntity(pos) instanceof CrystalPortalBlockEntity portal
+                    && holderPos.equals(portal.receptacle()),
+                    "Activation must retain every cell with the same book holder");
+        }
+        CrystalPortalNetwork.setLiveView(level, plan, true);
+        for (BlockPos pos : plan.portalCells()) {
+            ((CrystalPortalBlockEntity) level.getBlockEntity(pos))
+                    .loadWithComponents(new CompoundTag(), level.registryAccess());
+        }
+        helper.assertTrue(CrystalPortalNetwork.recoverSavedOwners(level, holderPos),
+                "An intact saved surface can recover its lost holder pointers without placing blocks");
+        for (BlockPos pos : plan.portalCells()) {
+            CrystalPortalBlockEntity portal = (CrystalPortalBlockEntity) level.getBlockEntity(pos);
+            helper.assertValueEqual(portal.receptacle(), holderPos,
+                    "Every recovered cell must point to the book holder");
+        }
         helper.succeed();
     }
+
+    @GameTest(template = "empty")
+    public static void portalCooldownIsIndependentAndSessionOnly(GameTestHelper helper) {
+        var first = helper.makeMockServerPlayerInLevel();
+        var second = helper.makeMockServerPlayerInLevel();
+        helper.assertTrue(!PortalTravelCooldown.blocked(5, -1),
+                "A player with no prior portal use must link immediately");
+        PortalTravelCooldown.mark(first, 100);
+        helper.assertTrue(PortalTravelCooldown.blocked(first, 105)
+                && !PortalTravelCooldown.blocked(second, 105),
+                "One player's loop protection must not block another player");
+        PortalTravelCooldown.clear();
+        helper.assertTrue(!PortalTravelCooldown.blocked(first, 105),
+                "A new server session must never inherit a saved portal cooldown");
+        helper.succeed();
+    }
+
+    private static CrystalPortalNetwork.Plan planLoaded(ServerLevel level, BlockPos holderPos) {
+        int chunkX = holderPos.getX() >> 4;
+        int chunkZ = holderPos.getZ() >> 4;
+        for (int x = chunkX - 1; x <= chunkX + 1; x++)
+            for (int z = chunkZ - 1; z <= chunkZ + 1; z++) level.getChunk(x, z);
+        return CrystalPortalNetwork.plan(level, holderPos);
+    }
 }

src/main/java/net/dnorberg/rivencraft/gametest/Milestone7AdvancementGameTests.java

@@ -0,0 +1,122 @@
+package net.dnorberg.rivencraft.gametest;
+
+import java.util.List;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.advancement.ProgressionAdvancements;
+import net.dnorberg.rivencraft.block.entity.InkMixerBlockEntity;
+import net.dnorberg.rivencraft.block.entity.WritingDeskBlockEntity;
+import net.dnorberg.rivencraft.item.PageItem;
+import net.dnorberg.rivencraft.menu.InkMixerMenu;
+import net.dnorberg.rivencraft.menu.WritingDeskMenu;
+import net.dnorberg.rivencraft.registry.ModBlocks;
+import net.dnorberg.rivencraft.registry.ModItems;
+import net.dnorberg.rivencraft.writing.SymbolReference;
+import net.minecraft.core.BlockPos;
+import net.minecraft.gametest.framework.GameTest;
+import net.minecraft.gametest.framework.GameTestHelper;
+import net.minecraft.resources.ResourceLocation;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.world.inventory.ClickType;
+import net.minecraft.world.item.ItemStack;
+import net.minecraft.world.item.Items;
+import net.neoforged.neoforge.gametest.GameTestHolder;
+import net.neoforged.neoforge.gametest.PrefixGameTestTemplate;
+
+@GameTestHolder(Rivencraft.MOD_ID)
+@PrefixGameTestTemplate(false)
+public final class Milestone7AdvancementGameTests {
+    private Milestone7AdvancementGameTests() {}
+
+    @GameTest(template = "empty")
+    public static void progressionAndRecipeUnlocksLoad(GameTestHelper helper) {
+        var registry = helper.getLevel().getServer().getAdvancements();
+        for (String path : List.of("root", "page", "linking_book", "link_panel",
+                "copy_page", "bind_age", "enter_age", "open_portal")) {
+            helper.assertTrue(registry.get(id("progression/" + path)) != null,
+                    "Progression advancement must load: " + path);
+        }
+        for (String path : List.of("book_binder", "book_receptacle", "crystal_block",
+                "ink_mixer", "ink_vial", "notebook", "writing_desk")) {
+            helper.assertTrue(registry.get(id("recipes/misc/" + path)) != null,
+                    "Recipe-book unlock must load: " + path);
+        }
+        var player = helper.makeMockServerPlayerInLevel();
+        for (String path : List.of("book_binder", "ink_mixer", "notebook", "writing_desk")) {
+            player.getAdvancements().award(registry.get(id("recipes/misc/" + path)), "has_material");
+            helper.assertTrue(player.getRecipeBook().contains(id(path)),
+                    "Discovering the material must unlock the " + path + " recipe");
+        }
+        helper.succeed();
+    }
+
+    @GameTest(template = "empty")
+    public static void actionAwardsAreServerOwnedAndPerPlayer(GameTestHelper helper) {
+        var first = helper.makeMockServerPlayerInLevel();
+        var second = helper.makeMockServerPlayerInLevel();
+        var advancement = helper.getLevel().getServer().getAdvancements().get(id("progression/copy_page"));
+        helper.assertFalse(first.getAdvancements().getOrStartProgress(advancement).isDone(),
+                "Opening a menu or preview must not award a copied Page");
+        helper.assertFalse(second.getAdvancements().getOrStartProgress(advancement).isDone(),
+                "Another player must not inherit the advancement");
+        ProgressionAdvancements.awardAgeTravel(first);
+        var travel = helper.getLevel().getServer().getAdvancements().get(id("progression/enter_age"));
+        helper.assertFalse(first.getAdvancements().getOrStartProgress(travel).isDone(),
+                "Overworld travel or a preview must not count as entering an Age");
+        ProgressionAdvancements.award(first, ProgressionAdvancements.COPY_PAGE);
+        helper.assertTrue(first.getAdvancements().getOrStartProgress(advancement).isDone(),
+                "The server must award the player who completed the action");
+        helper.assertFalse(second.getAdvancements().getOrStartProgress(advancement).isDone(),
+                "Advancement progress must remain per-player in multiplayer");
+        helper.succeed();
+    }
+
+    @GameTest(template = "empty")
+    public static void mixerPreviewDoesNotAwardButTakingPanelDoes(GameTestHelper helper) {
+        BlockPos pos = helper.absolutePos(new BlockPos(1, 1, 1));
+        helper.getLevel().setBlock(pos, ModBlocks.INK_MIXER.get().defaultBlockState(), 3);
+        var mixer = (InkMixerBlockEntity) helper.getLevel().getBlockEntity(pos);
+        mixer.setItem(InkMixerBlockEntity.PAPER, new ItemStack(Items.PAPER));
+        mixer.setItem(InkMixerBlockEntity.INK, new ItemStack(ModItems.INK_VIAL.get()));
+        var player = nearbyPlayer(helper, pos);
+        var menu = new InkMixerMenu(1, player.getInventory(), mixer);
+        helper.assertFalse(done(player, ProgressionAdvancements.LINK_PANEL),
+                "Opening the Ink Mixer must not award its milestone");
+        menu.clicked(InkMixerMenu.RESULT, 0, ClickType.PICKUP, player);
+        helper.assertTrue(done(player, ProgressionAdvancements.LINK_PANEL),
+                "Taking the completed Link Panel must award its milestone");
+        helper.succeed();
+    }
+
+    @GameTest(template = "empty")
+    public static void deskPreviewDoesNotAwardButCopyingDoes(GameTestHelper helper) {
+        BlockPos pos = helper.absolutePos(new BlockPos(1, 1, 1));
+        helper.getLevel().setBlock(pos, ModBlocks.WRITING_DESK.get().defaultBlockState(), 3);
+        var desk = (WritingDeskBlockEntity) helper.getLevel().getBlockEntity(pos);
+        desk.setItem(0, PageItem.createSymbolPage(new SymbolReference(id("terrain/standard"))));
+        desk.setItem(WritingDeskBlockEntity.PAPER, new ItemStack(Items.PAPER));
+        desk.setItem(WritingDeskBlockEntity.INK, new ItemStack(ModItems.INK_VIAL.get()));
+        var player = nearbyPlayer(helper, pos);
+        var menu = new WritingDeskMenu(1, player.getInventory(), desk);
+        helper.assertFalse(done(player, ProgressionAdvancements.COPY_PAGE),
+                "Opening the Writing Desk must not award a copied Page");
+        menu.clicked(WritingDeskMenu.COPY_RESULT, 0, ClickType.PICKUP, player);
+        helper.assertTrue(done(player, ProgressionAdvancements.COPY_PAGE),
+                "Taking a copied Page must award its milestone");
+        helper.succeed();
+    }
+
+    private static ServerPlayer nearbyPlayer(GameTestHelper helper, BlockPos pos) {
+        var player = helper.makeMockServerPlayerInLevel();
+        player.moveTo(pos.getX() + 0.5, pos.getY() + 0.5, pos.getZ() + 0.5);
+        return player;
+    }
+
+    private static boolean done(ServerPlayer player, String path) {
+        var advancement = player.getServer().getAdvancements().get(id("progression/" + path));
+        return player.getAdvancements().getOrStartProgress(advancement).isDone();
+    }
+
+    private static ResourceLocation id(String path) {
+        return ResourceLocation.fromNamespaceAndPath(Rivencraft.MOD_ID, path);
+    }
+}

src/main/java/net/dnorberg/rivencraft/gametest/Milestone7CraftingGameTests.java

@@ -0,0 +1,105 @@
+package net.dnorberg.rivencraft.gametest;
+
+import java.util.ArrayList;
+import java.util.List;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.item.PageItem;
+import net.dnorberg.rivencraft.registry.ModItems;
+import net.minecraft.gametest.framework.GameTest;
+import net.minecraft.gametest.framework.GameTestHelper;
+import net.minecraft.resources.ResourceLocation;
+import net.minecraft.world.item.ItemStack;
+import net.minecraft.world.item.Items;
+import net.minecraft.world.item.crafting.CraftingInput;
+import net.minecraft.world.item.crafting.RecipeType;
+import net.neoforged.neoforge.gametest.GameTestHolder;
+import net.neoforged.neoforge.gametest.PrefixGameTestTemplate;
+
+/** Data-driven Milestone 7 crafting checks; every result is obtained from the loaded recipe manager. */
+@GameTestHolder(Rivencraft.MOD_ID)
+@PrefixGameTestTemplate(false)
+public final class Milestone7CraftingGameTests {
+    private Milestone7CraftingGameTests() {}
+
+    @GameTest(template = "empty")
+    public static void crystalProgressionMatchesLegacyCounts(GameTestHelper helper) {
+        var level = helper.getLevel();
+        ItemStack shard = new ItemStack(ModItems.CRYSTAL_SHARD.get());
+        CraftingInput crystalInput = CraftingInput.of(2, 2, List.of(shard, shard, shard, shard));
+        var crystalRecipe = level.getRecipeManager().getRecipeFor(RecipeType.CRAFTING, crystalInput, level)
+                .orElseThrow();
+        helper.assertValueEqual(crystalRecipe.id(), id("crystal_block"),
+                "Four shards must craft a Crystal Block");
+        ItemStack crystal = crystalRecipe.value().assemble(crystalInput, level.registryAccess());
+        helper.assertTrue(crystal.is(ModItems.CRYSTAL_BLOCK.get()) && crystal.getCount() == 1,
+                "The shard recipe must yield one Crystal Block");
+
+        List<ItemStack> ring = new ArrayList<>();
+        for (int slot = 0; slot < 9; slot++) ring.add(slot == 4 ? ItemStack.EMPTY : crystal.copy());
+        CraftingInput receptacleInput = CraftingInput.of(3, 3, ring);
+        var receptacleRecipe = level.getRecipeManager()
+                .getRecipeFor(RecipeType.CRAFTING, receptacleInput, level).orElseThrow();
+        helper.assertValueEqual(receptacleRecipe.id(), id("book_receptacle"),
+                "The Legacy eight-block ring must craft the Receptacle");
+        ItemStack result = receptacleRecipe.value().assemble(receptacleInput, level.registryAccess());
+        helper.assertTrue(result.is(ModItems.BOOK_RECEPTACLE.get()) && result.getCount() == 1,
+                "One ring must yield exactly one Book Receptacle");
+        helper.assertTrue(receptacleRecipe.value().getRemainingItems(receptacleInput).stream()
+                .allMatch(ItemStack::isEmpty), "Crystal crafting must not duplicate source blocks as remainders");
+        ring.set(4, crystal.copy());
+        helper.assertTrue(level.getRecipeManager().getRecipeFor(RecipeType.CRAFTING,
+                CraftingInput.of(3, 3, ring), level).isEmpty(),
+                "A filled center must not match the Book Receptacle ring");
+        helper.succeed();
+    }
+
+    @GameTest(template = "empty")
+    public static void bucketInkReturnsItsContainer(GameTestHelper helper) {
+        var level = helper.getLevel();
+        ItemStack dye = new ItemStack(Items.BLACK_DYE);
+        CraftingInput bucketInput = CraftingInput.of(2, 2, List.of(
+                dye, dye, new ItemStack(Items.GLASS_BOTTLE), new ItemStack(Items.WATER_BUCKET)));
+        var bucketRecipe = level.getRecipeManager().getRecipeFor(RecipeType.CRAFTING, bucketInput, level)
+                .orElseThrow();
+        helper.assertValueEqual(bucketRecipe.id(), id("ink_vial"), "Bucket ink recipe must remain registered");
+        helper.assertTrue(bucketRecipe.value().assemble(bucketInput, level.registryAccess())
+                .is(ModItems.INK_VIAL.get()), "Bucket recipe must yield an Ink Vial");
+        helper.assertTrue(bucketRecipe.value().getRemainingItems(bucketInput).stream()
+                .anyMatch(stack -> stack.is(Items.BUCKET)), "The water bucket must return an empty bucket");
+
+        helper.succeed();
+    }
+
+    @GameTest(template = "empty")
+    public static void recipeUnlocksAreLoadedAndBlankPagesStayUncraftable(GameTestHelper helper) {
+        var level = helper.getLevel();
+        for (String path : List.of("crystal_block", "book_receptacle", "ink_vial")) {
+            helper.assertTrue(level.getServer().getAdvancements().get(id("recipes/misc/" + path)) != null,
+                    "Recipe unlock must load for " + path);
+        }
+        var player = helper.makeMockServerPlayerInLevel();
+        var shardUnlock = level.getServer().getAdvancements().get(id("recipes/misc/crystal_block"));
+        player.getAdvancements().award(shardUnlock, "has_crystal_shard");
+        helper.assertTrue(player.getRecipeBook().contains(id("crystal_block")),
+                "Discovering a shard must unlock the Crystal Block recipe");
+        var receptacleUnlock = level.getServer().getAdvancements().get(id("recipes/misc/book_receptacle"));
+        player.getAdvancements().award(receptacleUnlock, "has_crystal_block");
+        helper.assertTrue(player.getRecipeBook().contains(id("book_receptacle")),
+                "Discovering a Crystal Block must unlock the Receptacle recipe");
+        CraftingInput blankInput = CraftingInput.of(2, 2, List.of(
+                new ItemStack(Items.PAPER), new ItemStack(ModItems.INK_VIAL.get()),
+                ItemStack.EMPTY, ItemStack.EMPTY));
+        helper.assertTrue(level.getRecipeManager().getRecipeFor(RecipeType.CRAFTING, blankInput, level).isEmpty(),
+                "Blank Pages and Link Panels must not become grid-craftable");
+        ItemStack panel = PageItem.createLinkPanelPage();
+        CraftingInput linkInput = CraftingInput.of(2, 1, List.of(panel, new ItemStack(Items.LEATHER)));
+        helper.assertValueEqual(level.getRecipeManager().getRecipeFor(RecipeType.CRAFTING, linkInput, level)
+                .orElseThrow().id(), id("linking_book"),
+                "Link Panel crafting remains limited to the established Linking Book recipe");
+        helper.succeed();
+    }
+
+    private static ResourceLocation id(String path) {
+        return ResourceLocation.fromNamespaceAndPath(Rivencraft.MOD_ID, path);
+    }
+}

src/main/java/net/dnorberg/rivencraft/gametest/Milestone7PolishGameTests.java

@@ -0,0 +1,51 @@
+package net.dnorberg.rivencraft.gametest;
+
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.book.LinkProperties;
+import net.dnorberg.rivencraft.book.LinkVisualEffects;
+import net.dnorberg.rivencraft.registry.ModSounds;
+import net.minecraft.gametest.framework.GameTest;
+import net.minecraft.gametest.framework.GameTestHelper;
+import net.neoforged.neoforge.gametest.GameTestHolder;
+import net.neoforged.neoforge.gametest.PrefixGameTestTemplate;
+
+@GameTestHolder(Rivencraft.MOD_ID)
+@PrefixGameTestTemplate(false)
+public final class Milestone7PolishGameTests {
+    private Milestone7PolishGameTests() {}
+
+    @GameTest(template = "empty")
+    public static void modifierFlagsKeepLegacyIntraRules(GameTestHelper helper) {
+        LinkProperties linking = new LinkProperties(LinkProperties.DISARM | LinkProperties.INTRA_LINKING
+                | LinkProperties.INTRA_LINKING_ONLY | LinkProperties.RELATIVE_LINK
+                | LinkProperties.DISABLE_PLATFORM);
+        helper.assertTrue(linking.has(LinkProperties.INTRA_LINKING_ONLY)
+                        && linking.has(LinkProperties.RELATIVE_LINK)
+                        && linking.has(LinkProperties.DISABLE_PLATFORM),
+                "The new link options must retain independent flag values");
+        LinkProperties descriptive = linking.forDescriptiveBook();
+        helper.assertTrue(!descriptive.has(LinkProperties.INTRA_LINKING)
+                        && !descriptive.has(LinkProperties.INTRA_LINKING_ONLY),
+                "Intra-only controls must not constrain Descriptive Books");
+        helper.assertTrue(descriptive.has(LinkProperties.DISARM)
+                        && descriptive.has(LinkProperties.RELATIVE_LINK)
+                        && descriptive.has(LinkProperties.DISABLE_PLATFORM),
+                "Shared link options must remain active on Descriptive Books");
+        helper.succeed();
+    }
+
+    @GameTest(template = "empty")
+    public static void linkSoundPriorityMatchesLegacy(GameTestHelper helper) {
+        helper.assertTrue(LinkVisualEffects.sound(LinkProperties.NONE, false) == ModSounds.LINK.get(),
+                "Ordinary book travel uses the Legacy link sound");
+        helper.assertTrue(LinkVisualEffects.sound(new LinkProperties(LinkProperties.INTRA_LINKING), false)
+                        == ModSounds.LINK_INTRA.get(),
+                "Intra Linking uses its Legacy sound");
+        helper.assertTrue(LinkVisualEffects.sound(LinkProperties.NONE, true) == ModSounds.LINK_PORTAL.get(),
+                "Portal travel uses its Legacy sound");
+        helper.assertTrue(LinkVisualEffects.sound(new LinkProperties(LinkProperties.DISARM), true)
+                        == ModSounds.LINK_DISARM.get(),
+                "Legacy Disarm takes precedence over the portal sound");
+        helper.succeed();
+    }
+}

src/main/java/net/dnorberg/rivencraft/gametest/SymbolPortfolioGameTests.java

@@ -0,0 +1,59 @@
+package net.dnorberg.rivencraft.gametest;
+
+import java.util.ArrayList;
+import java.util.List;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.item.CollationFolderItem;
+import net.dnorberg.rivencraft.item.PageItem;
+import net.dnorberg.rivencraft.item.SymbolPortfolioItem;
+import net.dnorberg.rivencraft.registry.ModCreativeTabs;
+import net.dnorberg.rivencraft.registry.ModDataComponents;
+import net.dnorberg.rivencraft.registry.ModItems;
+import net.dnorberg.rivencraft.writing.NotebookContents;
+import net.dnorberg.rivencraft.writing.PageContent;
+import net.minecraft.gametest.framework.GameTest;
+import net.minecraft.gametest.framework.GameTestHelper;
+import net.minecraft.resources.ResourceLocation;
+import net.minecraft.world.item.ItemStack;
+import net.neoforged.neoforge.gametest.GameTestHolder;
+import net.neoforged.neoforge.gametest.PrefixGameTestTemplate;
+
+@GameTestHolder(Rivencraft.MOD_ID)
+@PrefixGameTestTemplate(false)
+public final class SymbolPortfolioGameTests {
+    private SymbolPortfolioGameTests() {}
+
+    @GameTest(template = "empty")
+    public static void portfoliosCoverEverySymbolCategoryWithoutTruncation(GameTestHelper helper) {
+        var registries = helper.getLevel().registryAccess();
+        List<ItemStack> creative = ModCreativeTabs.creativeSymbolPortfolios(registries);
+        helper.assertTrue(!creative.isEmpty(), "Creative tab must include prefilled portfolios");
+        for (ResourceLocation category : PageItem.bundledCreativeCategories()) {
+            List<ItemStack> expected = PageItem.creativeSymbolPages(registries, category);
+            List<ItemStack> volumes = SymbolPortfolioItem.createVolumes(category, expected);
+            helper.assertTrue(!volumes.isEmpty(), "Missing portfolio for " + category);
+            List<ItemStack> actual = new ArrayList<>();
+            for (ItemStack volume : volumes) {
+                helper.assertTrue(volume.is(ModItems.SYMBOL_PORTFOLIO.get())
+                                && CollationFolderItem.isCollection(volume)
+                                && creative.stream().anyMatch(candidate ->
+                                        candidate.getHoverName().getString().equals(volume.getHoverName().getString())),
+                        "Portfolio must be an editable creative collection for " + category);
+                NotebookContents contents = volume.get(ModDataComponents.NOTEBOOK_CONTENTS.get());
+                helper.assertTrue(contents != null && contents.pageCount() > 0
+                                && contents.pageCount() <= NotebookContents.MAX_PAGES,
+                        "Each portfolio volume must contain valid pages");
+                helper.assertTrue(contents.pages().stream().allMatch(page ->
+                                PageItem.content(page).kind() == PageContent.Kind.SYMBOL),
+                        "Portfolios must contain symbol pages, not Link Panels");
+                actual.addAll(contents.pages());
+            }
+            helper.assertTrue(actual.size() == expected.size(), "Portfolio omitted pages in " + category);
+            for (int index = 0; index < expected.size(); index++) {
+                helper.assertTrue(ItemStack.isSameItemSameComponents(actual.get(index), expected.get(index)),
+                        "Portfolio pages must match the category tab in " + category);
+            }
+        }
+        helper.succeed();
+    }
+}

src/main/java/net/dnorberg/rivencraft/gametest/WritingDataGameTests.java

@@ -151,11 +151,23 @@ public final class WritingDataGameTests {
                 "Zero must use Legacy's dedicated number mark");
         helper.assertTrue(Arrays.equals(SymbolNumerals.componentsForDigit(1), new int[] {56}),
                 "One must use Legacy's first bottom-row mark");
+        helper.assertTrue(Arrays.equals(SymbolNumerals.componentsForDigit(5), new int[] {60}),
+                "Five must use Legacy's first five-step mark");
+        helper.assertTrue(Arrays.equals(SymbolNumerals.componentsForDigit(10), new int[] {61}),
+                "Ten must use Legacy's second five-step mark");
+        helper.assertTrue(Arrays.equals(SymbolNumerals.componentsForDigit(14), new int[] {61, 59}),
+                "Fourteen must overlay the ten and four marks");
+        helper.assertTrue(Arrays.equals(SymbolNumerals.componentsForDigit(20), new int[] {63}),
+                "Twenty must use Legacy's final five-step mark");
         helper.assertTrue(Arrays.equals(SymbolNumerals.componentsForDigit(24), new int[] {63, 59}),
                 "Twenty-four must combine Legacy's five and unit marks");
         helper.assertTrue(Arrays.equals(SymbolNumerals.digitsFor(25), new int[] {1, 0}),
                 "Twenty-five must start a second base-25 place");
-        helper.assertTrue(Arrays.equals(SymbolNumerals.digitsFor(88), new int[] {3, 13}),
+        helper.assertTrue(Arrays.equals(SymbolNumerals.digitsFor(49), new int[] {1, 24}),
+                "Forty-nine must use twenty-four in its ones place");
+        helper.assertTrue(Arrays.equals(SymbolNumerals.digitsFor(50), new int[] {2, 0}),
+                "Fifty must carry into the second base-25 place");
+        helper.assertTrue(Arrays.equals(SymbolNumerals.digitsFor(87), new int[] {3, 12}),
                 "Last writing-desk tab must retain its numeric value");
 
         String display = "\"name\":\"symbol.example.test\","

src/main/java/net/dnorberg/rivencraft/item/CollationFolderItem.java

@@ -0,0 +1,25 @@
+package net.dnorberg.rivencraft.item;
+
+import net.dnorberg.rivencraft.registry.ModItems;
+import net.dnorberg.rivencraft.writing.NotebookContents;
+import net.minecraft.world.item.ItemStack;
+
+/** Legacy's compact page collection, using the existing Notebook page editor. */
+public final class CollationFolderItem extends NotebookItem {
+    public static final int MAX_PAGES = 27;
+
+    public CollationFolderItem(Properties properties) {
+        super(properties);
+    }
+
+    public static boolean isCollection(ItemStack stack) {
+        return stack.is(ModItems.NOTEBOOK.get()) || stack.is(ModItems.COLLATION_FOLDER.get())
+                || stack.is(ModItems.SYMBOL_PORTFOLIO.get());
+    }
+
+    public static int capacity(ItemStack stack) {
+        return stack.is(ModItems.COLLATION_FOLDER.get()) ? MAX_PAGES
+                : stack.is(ModItems.NOTEBOOK.get()) || stack.is(ModItems.SYMBOL_PORTFOLIO.get())
+                        ? NotebookContents.MAX_PAGES : 0;
+    }
+}

src/main/java/net/dnorberg/rivencraft/item/DescriptiveBookItem.java

@@ -1,26 +1,28 @@
 package net.dnorberg.rivencraft.item;
 
+import net.dnorberg.rivencraft.advancement.ProgressionAdvancements;
 import java.util.List;
 import net.dnorberg.rivencraft.book.AgeReference;
 import net.dnorberg.rivencraft.book.AgeVisitSavedData;
 import net.dnorberg.rivencraft.book.LinkTarget;
 import net.dnorberg.rivencraft.book.LinkProperties;
 import net.dnorberg.rivencraft.book.LinkingService;
+import net.dnorberg.rivencraft.book.LinkVisualEffects;
 import net.dnorberg.rivencraft.book.AgeDimensionService;
 import net.dnorberg.rivencraft.config.RivencraftConfig;
 import net.dnorberg.rivencraft.registry.ModDataComponents;
 import net.dnorberg.rivencraft.registry.ModItems;
-import net.dnorberg.rivencraft.registry.ModSounds;
 import net.minecraft.ChatFormatting;
 import net.minecraft.core.component.DataComponents;
 import net.minecraft.network.chat.Component;
 import net.minecraft.network.chat.MutableComponent;
 import net.minecraft.server.level.ServerPlayer;
-import net.minecraft.sounds.SoundSource;
 import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.InteractionHand;
 import net.minecraft.world.item.Item;
 import net.minecraft.world.item.ItemStack;
 import net.minecraft.world.item.TooltipFlag;
+import net.minecraft.world.phys.Vec3;
 
 /**
  * A book that will eventually describe and link to a generated Age.
@@ -40,14 +42,18 @@ public final class DescriptiveBookItem extends Item {
     }
 
     public static boolean useWrittenBook(ServerPlayer player, ItemStack stack) {
-        return useWrittenBook(player, stack, false);
+        return useWrittenBook(player, stack, false, null);
+    }
+
+    public static boolean useHandheldBook(ServerPlayer player, InteractionHand hand) {
+        return useWrittenBook(player, player.getItemInHand(hand), false, hand);
     }
 
     public static boolean usePortalBook(ServerPlayer player, ItemStack stack) {
-        return useWrittenBook(player, stack, true);
+        return useWrittenBook(player, stack, true, null);
     }
 
-    private static boolean useWrittenBook(ServerPlayer player, ItemStack stack, boolean portal) {
+    private static boolean useWrittenBook(ServerPlayer player, ItemStack stack, boolean portal, InteractionHand hand) {
         AgeReference age = stack.get(ModDataComponents.AGE_REFERENCE.get());
         if (age == null) {
             player.displayClientMessage(Component.translatable("message.rivencraft.descriptive_book.unwritten"), true);
@@ -55,19 +61,21 @@ public final class DescriptiveBookItem extends Item {
         }
 
         LinkTarget returnTarget = LinkTarget.from(player);
-        LinkTarget ageTarget = AgeDimensionService.resolve(player, age).orElse(null);
+        LinkProperties properties = stack.getOrDefault(ModDataComponents.LINK_PROPERTIES.get(), LinkProperties.NONE)
+                .forDescriptiveBook();
+        LinkTarget ageTarget = AgeDimensionService.resolve(player, age, net.dnorberg.rivencraft.writing.OrderedWriting.EMPTY,
+                !properties.has(LinkProperties.DISABLE_PLATFORM)).orElse(null);
         if (ageTarget == null) {
             player.displayClientMessage(Component.translatable("message.rivencraft.descriptive_book.unavailable"), true);
             return false;
         }
 
         ServerLevel sourceLevel = player.serverLevel();
-        var sourcePosition = player.blockPosition();
-        LinkProperties properties = stack.getOrDefault(ModDataComponents.LINK_PROPERTIES.get(), LinkProperties.NONE)
-                .forDescriptiveBook();
+        Vec3 sourcePosition = player.position();
         LinkingService.LinkResult result = portal
                 ? LinkingService.travelDescriptivePortal(player, ageTarget, properties)
-                : LinkingService.travelWithFooting(player, ageTarget, properties);
+                : hand == null ? LinkingService.travelWithFooting(player, ageTarget, properties)
+                : LinkingService.travelHandheld(player, hand, stack, ageTarget, properties, true);
         if (result != LinkingService.LinkResult.SUCCESS) {
             player.displayClientMessage(Component.translatable("message.rivencraft.descriptive_book.unsafe"), true);
             return false;
@@ -85,10 +93,8 @@ public final class DescriptiveBookItem extends Item {
                 player.drop(returnBook, false);
             }
         }
-        sourceLevel.playSound(null, sourcePosition, (portal ? ModSounds.LINK_PORTAL : ModSounds.LINK).get(), SoundSource.PLAYERS,
-                0.8F, sourceLevel.random.nextFloat() * 0.2F + 0.9F);
-        player.level().playSound(null, player.blockPosition(), (portal ? ModSounds.LINK_PORTAL : ModSounds.LINK).get(), SoundSource.PLAYERS,
-                0.8F, player.level().random.nextFloat() * 0.2F + 0.9F);
+        LinkVisualEffects.play(sourceLevel, sourcePosition, player, properties, portal);
+        ProgressionAdvancements.awardAgeTravel(player);
         player.displayClientMessage(Component.translatable(
                 createReturnLink ? "message.rivencraft.descriptive_book.linked_first" : "message.rivencraft.descriptive_book.linked",
                 age.name()

src/main/java/net/dnorberg/rivencraft/item/LinkingBookItem.java

@@ -1,19 +1,19 @@
 package net.dnorberg.rivencraft.item;
 
+import net.dnorberg.rivencraft.advancement.ProgressionAdvancements;
 import java.util.List;
 import net.dnorberg.rivencraft.book.LinkTarget;
 import net.dnorberg.rivencraft.book.AgeRegistrySavedData;
 import net.dnorberg.rivencraft.book.LinkingService;
+import net.dnorberg.rivencraft.book.LinkVisualEffects;
 import net.dnorberg.rivencraft.book.LinkProperties;
 import net.dnorberg.rivencraft.registry.ModDataComponents;
-import net.dnorberg.rivencraft.registry.ModSounds;
 import net.minecraft.ChatFormatting;
 import net.minecraft.core.BlockPos;
 import net.minecraft.network.chat.Component;
 import net.minecraft.resources.ResourceLocation;
 import net.minecraft.server.level.ServerPlayer;
 import net.minecraft.server.level.ServerLevel;
-import net.minecraft.sounds.SoundSource;
 import net.minecraft.world.InteractionHand;
 import net.minecraft.world.InteractionResultHolder;
 import net.minecraft.world.entity.player.Player;
@@ -21,6 +21,7 @@ import net.minecraft.world.item.Item;
 import net.minecraft.world.item.ItemStack;
 import net.minecraft.world.item.TooltipFlag;
 import net.minecraft.world.level.Level;
+import net.minecraft.world.phys.Vec3;
 
 public final class LinkingBookItem extends Item {
     public LinkingBookItem(Properties properties) {
@@ -42,35 +43,35 @@ public final class LinkingBookItem extends Item {
     }
 
     public static InteractionResultHolder<ItemStack> useBoundBook(ServerPlayer player, ItemStack stack) {
-        return useBoundBook(player, stack, false);
+        return useBoundBook(player, stack, false, null);
+    }
+
+    public static InteractionResultHolder<ItemStack> useHandheldBook(ServerPlayer player, InteractionHand hand) {
+        return useBoundBook(player, player.getItemInHand(hand), false, hand);
     }
 
     public static InteractionResultHolder<ItemStack> usePortalBook(ServerPlayer player, ItemStack stack) {
-        return useBoundBook(player, stack, true);
+        return useBoundBook(player, stack, true, null);
     }
 
-    private static InteractionResultHolder<ItemStack> useBoundBook(ServerPlayer player, ItemStack stack, boolean portal) {
+    private static InteractionResultHolder<ItemStack> useBoundBook(ServerPlayer player, ItemStack stack, boolean portal,
+                                                                   InteractionHand hand) {
         LinkTarget target = stack.get(ModDataComponents.LINK_TARGET.get());
         if (target == null) {
             player.displayClientMessage(Component.translatable("message.rivencraft.linking_book.unbound"), true);
             return InteractionResultHolder.fail(stack);
         }
 
-        Level sourceLevel = player.level();
-        BlockPos sourcePosition = player.blockPosition();
+        ServerLevel sourceLevel = player.serverLevel();
+        Vec3 sourcePosition = player.position();
         LinkProperties properties = stack.getOrDefault(ModDataComponents.LINK_PROPERTIES.get(), LinkProperties.NONE);
-        LinkingService.LinkResult result = LinkingService.travel(player, target, properties);
+        LinkingService.LinkResult result = portal
+                ? LinkingService.travelPortal(player, target, properties)
+                : hand == null ? LinkingService.travel(player, target, properties)
+                : LinkingService.travelHandheld(player, hand, stack, target, properties, false);
         if (result == LinkingService.LinkResult.SUCCESS) {
-            sourceLevel.playSound(null, sourcePosition, (portal ? ModSounds.LINK_PORTAL : ModSounds.LINK).get(), SoundSource.PLAYERS,
-                    0.8F, sourceLevel.random.nextFloat() * 0.2F + 0.9F);
-            player.level().playSound(
-                    null,
-                    player.blockPosition(),
-                    (portal ? ModSounds.LINK_PORTAL : ModSounds.LINK).get(),
-                    SoundSource.PLAYERS,
-                    0.8F,
-                    player.level().random.nextFloat() * 0.2F + 0.9F
-            );
+            LinkVisualEffects.play(sourceLevel, sourcePosition, player, properties, portal);
+            ProgressionAdvancements.awardAgeTravel(player);
             player.displayClientMessage(Component.translatable("message.rivencraft.linking_book.linked"), true);
             return InteractionResultHolder.success(stack);
         }
@@ -78,6 +79,7 @@ public final class LinkingBookItem extends Item {
         String errorKey = switch (result) {
             case MISSING_DIMENSION -> "message.rivencraft.linking_book.missing_dimension";
             case INTRA_LINKING_REQUIRED -> "message.rivencraft.linking_book.intra_required";
+            case INTRA_ONLY -> "message.rivencraft.linking_book.intra_only";
             default -> "message.rivencraft.linking_book.unsafe";
         };
         player.displayClientMessage(Component.translatable(errorKey), true);

src/main/java/net/dnorberg/rivencraft/item/NotebookItem.java

@@ -16,7 +16,7 @@ import net.minecraft.world.item.ItemStack;
 import net.minecraft.world.item.TooltipFlag;
 import net.minecraft.world.level.Level;
 
-public final class NotebookItem extends Item {
+public class NotebookItem extends Item {
     public NotebookItem(Properties properties) {
         super(properties);
     }
@@ -39,7 +39,8 @@ public final class NotebookItem extends Item {
         NotebookContents contents = stack.getOrDefault(
                 ModDataComponents.NOTEBOOK_CONTENTS.get(), NotebookContents.EMPTY);
         tooltip.add(Component.translatable("item.rivencraft.notebook.pages",
-                contents.pageCount(), NotebookContents.MAX_PAGES).withStyle(ChatFormatting.GRAY));
+                contents.pageCount(), CollationFolderItem.capacity(stack))
+                .withStyle(ChatFormatting.GRAY));
         if (contents.unresolvedCount() > 0) {
             tooltip.add(Component.translatable("item.rivencraft.notebook.unresolved",
                     contents.unresolvedCount()).withStyle(ChatFormatting.RED));

src/main/java/net/dnorberg/rivencraft/item/SealedNotebookItem.java

@@ -0,0 +1,62 @@
+package net.dnorberg.rivencraft.item;
+
+import java.util.ArrayList;
+import java.util.List;
+import net.dnorberg.rivencraft.registry.ModDataComponents;
+import net.dnorberg.rivencraft.registry.ModItems;
+import net.dnorberg.rivencraft.writing.NotebookContents;
+import net.dnorberg.rivencraft.writing.SymbolCatalog;
+import net.dnorberg.rivencraft.writing.SymbolReference;
+import net.minecraft.resources.ResourceLocation;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.world.InteractionHand;
+import net.minecraft.world.InteractionResultHolder;
+import net.minecraft.world.entity.player.Player;
+import net.minecraft.world.item.Item;
+import net.minecraft.world.item.ItemStack;
+import net.minecraft.world.level.Level;
+
+/** Opens into a 16-page Collation Folder, as Legacy's booster item did. */
+public final class SealedNotebookItem extends Item {
+    private static final int PAGE_COUNT = 16;
+
+    public SealedNotebookItem(Properties properties) {
+        super(properties);
+    }
+
+    @Override
+    public InteractionResultHolder<ItemStack> use(Level level, Player player, InteractionHand hand) {
+        ItemStack sealed = player.getItemInHand(hand);
+        if (level.isClientSide) return InteractionResultHolder.sidedSuccess(sealed, true);
+        if (!(player instanceof ServerPlayer serverPlayer)) return InteractionResultHolder.pass(sealed);
+        ItemStack folder = open(serverPlayer);
+        if (folder.isEmpty()) return InteractionResultHolder.fail(sealed);
+        if (!player.hasInfiniteMaterials()) sealed.shrink(1);
+        if (sealed.isEmpty()) {
+            player.setItemInHand(hand, folder);
+        } else if (!player.getInventory().add(folder)) {
+            player.drop(folder, false);
+        }
+        return InteractionResultHolder.success(player.getItemInHand(hand));
+    }
+
+    static ItemStack open(ServerPlayer player) {
+        // Current symbol definitions have no Legacy rank. Draw from the authored
+        // symbol pool, excluding virtual block/biome pages and corrupted pages.
+        List<ResourceLocation> candidates = SymbolCatalog.symbols().entrySet().stream()
+                .filter(entry -> entry.getKey().getNamespace().equals("rivencraft")
+                        && !entry.getKey().getPath().startsWith("block/")
+                        && !entry.getKey().getPath().startsWith("biome/")
+                        && !entry.getValue().category().getPath().equals("corrupted"))
+                .map(java.util.Map.Entry::getKey).sorted().toList();
+        if (candidates.isEmpty()) return ItemStack.EMPTY;
+        List<ItemStack> pages = new ArrayList<>(PAGE_COUNT);
+        for (int i = 0; i < PAGE_COUNT; i++) {
+            ResourceLocation id = candidates.get(player.getRandom().nextInt(candidates.size()));
+            pages.add(PageItem.createSymbolPage(new SymbolReference(id)));
+        }
+        ItemStack folder = new ItemStack(ModItems.COLLATION_FOLDER.get());
+        folder.set(ModDataComponents.NOTEBOOK_CONTENTS.get(), new NotebookContents(pages));
+        return folder;
+    }
+}

src/main/java/net/dnorberg/rivencraft/item/SymbolPortfolioItem.java

@@ -0,0 +1,40 @@
+package net.dnorberg.rivencraft.item;
+
+import java.util.ArrayList;
+import java.util.List;
+import net.dnorberg.rivencraft.registry.ModDataComponents;
+import net.dnorberg.rivencraft.registry.ModItems;
+import net.dnorberg.rivencraft.writing.NotebookContents;
+import net.minecraft.core.component.DataComponents;
+import net.minecraft.network.chat.Component;
+import net.minecraft.resources.ResourceLocation;
+import net.minecraft.world.item.ItemStack;
+
+/** Non-craftable, prefilled Legacy-style collections of one symbol-page category. */
+public final class SymbolPortfolioItem extends NotebookItem {
+    public SymbolPortfolioItem(Properties properties) {
+        super(properties);
+    }
+
+    public static List<ItemStack> createVolumes(ResourceLocation category, List<ItemStack> pages) {
+        if (pages.isEmpty()) return List.of();
+        int capacity = NotebookContents.MAX_PAGES;
+        int volumeCount = (pages.size() + capacity - 1) / capacity;
+        List<ItemStack> volumes = new ArrayList<>(volumeCount);
+        for (int volume = 0; volume < volumeCount; volume++) {
+            ItemStack portfolio = new ItemStack(ModItems.SYMBOL_PORTFOLIO.get());
+            int first = volume * capacity;
+            int last = Math.min(first + capacity, pages.size());
+            portfolio.set(ModDataComponents.NOTEBOOK_CONTENTS.get(),
+                    new NotebookContents(pages.subList(first, last)));
+            Component categoryName = Component.translatableWithFallback(
+                    "itemGroup.rivencraft.pages." + category.getPath(), category.getPath());
+            portfolio.set(DataComponents.CUSTOM_NAME, volumeCount == 1
+                    ? Component.translatable("item.rivencraft.symbol_portfolio.named", categoryName)
+                    : Component.translatable("item.rivencraft.symbol_portfolio.volume",
+                            categoryName, volume + 1, volumeCount));
+            volumes.add(portfolio);
+        }
+        return List.copyOf(volumes);
+    }
+}

src/main/java/net/dnorberg/rivencraft/menu/BookBinderMenu.java

@@ -1,14 +1,17 @@
 package net.dnorberg.rivencraft.menu;
 
+import net.dnorberg.rivencraft.advancement.ProgressionAdvancements;
 import java.util.Optional;
 import net.dnorberg.rivencraft.block.entity.BookBinderBlockEntity;
 import net.dnorberg.rivencraft.item.PageItem;
 import net.dnorberg.rivencraft.registry.ModDataComponents;
 import net.dnorberg.rivencraft.registry.ModItems;
+import net.dnorberg.rivencraft.item.CollationFolderItem;
 import net.dnorberg.rivencraft.registry.ModMenus;
 import net.dnorberg.rivencraft.writing.PageContent;
 import net.dnorberg.rivencraft.writing.WritingGrammar;
 import net.minecraft.network.RegistryFriendlyByteBuf;
+import net.minecraft.server.level.ServerPlayer;
 import net.minecraft.world.Container;
 import net.minecraft.world.SimpleContainer;
 import net.minecraft.world.entity.player.Inventory;
@@ -170,7 +173,7 @@ public final class BookBinderMenu extends AbstractContainerMenu {
 
     private boolean clickStrip(int index) {
         ItemStack carried = getCarried();
-        if (carried.is(ModItems.NOTEBOOK.get())) {
+        if (CollationFolderItem.isCollection(carried)) {
             ItemStack emptied = binder.importNotebookFromStack(carried, Math.min(index == 0 ? 0 : index - 1,
                     binder.nextPageIndex()));
             if (emptied.isEmpty()) return false;
@@ -210,7 +213,9 @@ public final class BookBinderMenu extends AbstractContainerMenu {
             if (!moveItemStackTo(remainder, PLAYER_START, slots.size(), true) || !remainder.isEmpty()) {
                 return ItemStack.EMPTY;
             }
-            binder.consumeAssembly();
+            if (!binder.consumeAssembly()) return ItemStack.EMPTY;
+            if (player instanceof ServerPlayer serverPlayer)
+                ProgressionAdvancements.award(serverPlayer, ProgressionAdvancements.BIND_AGE);
             refreshResult();
             return book;
         }
@@ -223,7 +228,7 @@ public final class BookBinderMenu extends AbstractContainerMenu {
             moved = moveItemStackTo(source, PLAYER_START, slots.size(), true);
         } else if (source.is(Items.LEATHER) || BookBinderBlockEntity.validCover(source)) {
             moved = moveItemStackTo(source, BookBinderBlockEntity.COVER, BookBinderBlockEntity.COVER + 1, false);
-        } else if (source.is(ModItems.NOTEBOOK.get())) {
+        } else if (CollationFolderItem.isCollection(source)) {
             ItemStack emptied = binder.importNotebookFromStack(source, binder.nextPageIndex());
             if (emptied.isEmpty()) return ItemStack.EMPTY;
             sourceSlot.setByPlayer(emptied);
@@ -284,7 +289,11 @@ public final class BookBinderMenu extends AbstractContainerMenu {
             return clientSide ? hasItem() : stillValid(player) && binder.canAssemble();
         }
         @Override public void onTake(Player player, ItemStack stack) {
-            if (!clientSide && binder.consumeAssembly()) refreshResult();
+            if (!clientSide && binder.consumeAssembly()) {
+                if (player instanceof ServerPlayer serverPlayer)
+                    ProgressionAdvancements.award(serverPlayer, ProgressionAdvancements.BIND_AGE);
+                refreshResult();
+            }
             super.onTake(player, stack);
         }
     }

src/main/java/net/dnorberg/rivencraft/menu/InkMixerMenu.java

@@ -1,10 +1,12 @@
 package net.dnorberg.rivencraft.menu;
 
+import net.dnorberg.rivencraft.advancement.ProgressionAdvancements;
 import net.dnorberg.rivencraft.block.entity.InkMixerBlockEntity;
 import net.dnorberg.rivencraft.item.PageItem;
 import net.dnorberg.rivencraft.registry.ModItems;
 import net.dnorberg.rivencraft.registry.ModMenus;
 import net.minecraft.network.RegistryFriendlyByteBuf;
+import net.minecraft.server.level.ServerPlayer;
 import net.minecraft.world.Container;
 import net.minecraft.world.SimpleContainer;
 import net.minecraft.world.entity.player.Inventory;
@@ -109,6 +111,8 @@ public final class InkMixerMenu extends AbstractContainerMenu {
             if (!moveItemStackTo(remainder, PLAYER_START, slots.size(), true) || !remainder.isEmpty())
                 return ItemStack.EMPTY;
             if (!mixer.consumeLinkPanelMaterials()) return ItemStack.EMPTY;
+            if (player instanceof ServerPlayer serverPlayer)
+                ProgressionAdvancements.award(serverPlayer, ProgressionAdvancements.LINK_PANEL);
             refreshResult();
             return output;
         }
@@ -148,7 +152,11 @@ public final class InkMixerMenu extends AbstractContainerMenu {
             return clientSide ? hasItem() : stillValid(player) && mixer.canCreateLinkPanel();
         }
         @Override public void onTake(Player player, ItemStack stack) {
-            if (!clientSide && mixer.consumeLinkPanelMaterials()) refreshResult();
+            if (!clientSide && mixer.consumeLinkPanelMaterials()) {
+                if (player instanceof ServerPlayer serverPlayer)
+                    ProgressionAdvancements.award(serverPlayer, ProgressionAdvancements.LINK_PANEL);
+                refreshResult();
+            }
             super.onTake(player, stack);
         }
     }

src/main/java/net/dnorberg/rivencraft/menu/LinkModifierMenu.java

@@ -0,0 +1,201 @@
+package net.dnorberg.rivencraft.menu;
+
+import java.util.UUID;
+import net.dnorberg.rivencraft.block.entity.LinkModifierBlockEntity;
+import net.dnorberg.rivencraft.book.AgeDefinition;
+import net.dnorberg.rivencraft.book.AgeDeletionService;
+import net.dnorberg.rivencraft.book.AgeReference;
+import net.dnorberg.rivencraft.book.AgeRegistrySavedData;
+import net.dnorberg.rivencraft.book.LinkProperties;
+import net.dnorberg.rivencraft.registry.ModDataComponents;
+import net.dnorberg.rivencraft.registry.ModItems;
+import net.dnorberg.rivencraft.registry.ModMenus;
+import net.minecraft.core.component.DataComponents;
+import net.minecraft.network.RegistryFriendlyByteBuf;
+import net.minecraft.network.chat.Component;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.world.Container;
+import net.minecraft.world.SimpleContainer;
+import net.minecraft.world.entity.player.Inventory;
+import net.minecraft.world.entity.player.Player;
+import net.minecraft.world.inventory.AbstractContainerMenu;
+import net.minecraft.world.inventory.DataSlot;
+import net.minecraft.world.inventory.Slot;
+import net.minecraft.world.item.ItemStack;
+
+/** Server-owned book edits and a two-stage, OP-only Age retirement control. */
+public final class LinkModifierMenu extends AbstractContainerMenu {
+    public static final int TOGGLE_DISARM = 1;
+    public static final int TOGGLE_MOMENTUM = 2;
+    public static final int TOGGLE_INTRA = 3;
+    public static final int DELETE_AGE = 4;
+    public static final int TOGGLE_INTRA_ONLY = 5;
+    public static final int TOGGLE_RELATIVE = 6;
+    public static final int TOGGLE_PLATFORM = 7;
+    private static final int PLAYER_START = 1;
+    private static final int MAX_TITLE_LENGTH = 32;
+
+    private final LinkModifierBlockEntity modifier;
+    private final Container bookSlot;
+    private final boolean clientSide;
+    private final Player owner;
+    private final int[] seedWords = new int[4];
+    private int confirmation;
+    private UUID pendingAge;
+
+    public LinkModifierMenu(int id, Inventory inventory, RegistryFriendlyByteBuf data) {
+        this(id, inventory, inventory.player.level().getBlockEntity(data.readBlockPos())
+                instanceof LinkModifierBlockEntity found ? found : null);
+    }
+
+    public LinkModifierMenu(int id, Inventory inventory, LinkModifierBlockEntity modifier) {
+        super(ModMenus.LINK_MODIFIER.get(), id);
+        this.modifier = modifier;
+        this.bookSlot = modifier == null ? new SimpleContainer(1) : modifier;
+        this.clientSide = inventory.player.level().isClientSide;
+        this.owner = inventory.player;
+        addDataSlot(new DataSlot() {
+            @Override public int get() { return confirmation; }
+            @Override public void set(int value) { confirmation = value; }
+        });
+        for (int index = 0; index < seedWords.length; index++) {
+            final int word = index;
+            addDataSlot(new DataSlot() {
+                @Override public int get() {
+                    return clientSide ? seedWords[word] : (int) ((seed() >>> (word * 16)) & 0xffffL);
+                }
+                @Override public void set(int value) { seedWords[word] = value & 0xffff; }
+            });
+        }
+        addSlot(new Slot(bookSlot, 0, 80, 35) {
+            @Override public boolean mayPlace(ItemStack stack) { return bookSlot.canPlaceItem(0, stack); }
+            @Override public int getMaxStackSize() { return 1; }
+            @Override public void setChanged() {
+                super.setChanged();
+                pendingAge = null;
+                confirmation = 0;
+            }
+        });
+        for (int row = 0; row < 3; row++) for (int col = 0; col < 9; col++)
+            addSlot(new Slot(inventory, col + row * 9 + 9, 8 + col * 18, 84 + row * 18));
+        for (int col = 0; col < 9; col++)
+            addSlot(new Slot(inventory, col, 8 + col * 18, 142));
+    }
+
+    public ItemStack book() { return bookSlot.getItem(0); }
+    public boolean hasSeed() {
+        return book().is(ModItems.DESCRIPTIVE_BOOK.get())
+                && book().has(ModDataComponents.AGE_REFERENCE.get());
+    }
+    public long seed() {
+        if (clientSide) {
+            long result = 0;
+            for (int index = 0; index < seedWords.length; index++)
+                result |= (seedWords[index] & 0xffffL) << (index * 16);
+            return result;
+        }
+        if (!hasSeed()) return 0;
+        AgeReference reference = book().get(ModDataComponents.AGE_REFERENCE.get());
+        return AgeRegistrySavedData.get(((ServerPlayer) owner).serverLevel()).find(reference.id())
+                .map(AgeDefinition::seed).orElse(0L);
+    }
+
+    public boolean setSeed(Player player, String text) {
+        if (clientSide || !stillValid(player) || !hasSeed() || text == null || text.length() > 21
+                || !(player instanceof ServerPlayer serverPlayer)) return false;
+        long requested;
+        try { requested = Long.parseLong(text.strip()); }
+        catch (NumberFormatException exception) { return false; }
+        AgeReference reference = book().get(ModDataComponents.AGE_REFERENCE.get());
+        if (reference == null) return false;
+        boolean changed = AgeRegistrySavedData.get(serverPlayer.serverLevel())
+                .reseed(serverPlayer.getServer(), reference.id(), requested);
+        player.displayClientMessage(Component.translatable(changed
+                ? "message.rivencraft.link_modifier.seed_changed"
+                : "message.rivencraft.link_modifier.seed_failed"), false);
+        if (changed) broadcastChanges();
+        return changed;
+    }
+    public boolean awaitingDeletionConfirmation() { return confirmation == 1; }
+    public boolean canDelete(Player player) {
+        return player.hasPermissions(2) && book().is(ModItems.DESCRIPTIVE_BOOK.get())
+                && book().has(ModDataComponents.AGE_REFERENCE.get());
+    }
+
+    public boolean setTitle(Player player, String title) {
+        if (clientSide || !stillValid(player) || title == null || title.length() > MAX_TITLE_LENGTH
+                || book().isEmpty()) return false;
+        String clean = title.strip();
+        if (clean.isEmpty()) book().remove(DataComponents.CUSTOM_NAME);
+        else book().set(DataComponents.CUSTOM_NAME, Component.literal(clean));
+        bookSlot.setChanged();
+        broadcastChanges();
+        return true;
+    }
+
+    @Override public boolean clickMenuButton(Player player, int id) {
+        if (clientSide || !stillValid(player) || book().isEmpty()) return false;
+        if (id == DELETE_AGE) return retireAge(player);
+        int flag = switch (id) {
+            case TOGGLE_DISARM -> LinkProperties.DISARM;
+            case TOGGLE_MOMENTUM -> LinkProperties.MAINTAIN_MOMENTUM;
+            case TOGGLE_INTRA -> LinkProperties.INTRA_LINKING;
+            case TOGGLE_INTRA_ONLY -> LinkProperties.INTRA_LINKING_ONLY;
+            case TOGGLE_RELATIVE -> LinkProperties.RELATIVE_LINK;
+            case TOGGLE_PLATFORM -> book().is(ModItems.LINKING_BOOK.get())
+                    ? LinkProperties.GENERATE_PLATFORM : LinkProperties.DISABLE_PLATFORM;
+            default -> 0;
+        };
+        if (flag == 0 || ((flag == LinkProperties.INTRA_LINKING || flag == LinkProperties.INTRA_LINKING_ONLY)
+                && book().is(ModItems.DESCRIPTIVE_BOOK.get()))) return false;
+        int flags = book().getOrDefault(ModDataComponents.LINK_PROPERTIES.get(), LinkProperties.NONE).flags();
+        if (flag == LinkProperties.INTRA_LINKING_ONLY && (flags & LinkProperties.INTRA_LINKING_ONLY) == 0)
+            flags |= LinkProperties.INTRA_LINKING;
+        if (flag == LinkProperties.INTRA_LINKING && (flags & LinkProperties.INTRA_LINKING) != 0)
+            flags &= ~LinkProperties.INTRA_LINKING_ONLY;
+        book().set(ModDataComponents.LINK_PROPERTIES.get(), new LinkProperties(flags ^ flag));
+        bookSlot.setChanged();
+        pendingAge = null;
+        confirmation = 0;
+        broadcastChanges();
+        return true;
+    }
+
+    private boolean retireAge(Player player) {
+        if (!(player instanceof ServerPlayer serverPlayer) || !canDelete(player)) return false;
+        AgeReference reference = book().get(ModDataComponents.AGE_REFERENCE.get());
+        if (reference == null) return false;
+        AgeDefinition age = AgeRegistrySavedData.get(serverPlayer.serverLevel()).find(reference.id()).orElse(null);
+        if (age == null) return false;
+        if (confirmation != 1 || !reference.id().equals(pendingAge)) {
+            pendingAge = reference.id();
+            confirmation = 1;
+            broadcastChanges();
+            return true;
+        }
+        confirmation = 0;
+        pendingAge = null;
+        AgeDeletionService.Result result = AgeDeletionService.retire(serverPlayer.getServer(), age);
+        player.displayClientMessage(Component.translatable(
+                "message.rivencraft.link_modifier.delete." + result.name().toLowerCase()), false);
+        broadcastChanges();
+        return result == AgeDeletionService.Result.RETIRED;
+    }
+
+    @Override public boolean stillValid(Player player) {
+        return modifier != null && modifier.stillValid(player);
+    }
+
+    @Override public ItemStack quickMoveStack(Player player, int index) {
+        Slot slot = slots.get(index);
+        if (!slot.hasItem()) return ItemStack.EMPTY;
+        ItemStack source = slot.getItem();
+        ItemStack copy = source.copy();
+        if (index == 0) {
+            if (!moveItemStackTo(source, PLAYER_START, slots.size(), true)) return ItemStack.EMPTY;
+        } else if (!moveItemStackTo(source, 0, 1, false)) return ItemStack.EMPTY;
+        if (source.isEmpty()) slot.set(ItemStack.EMPTY);
+        else slot.setChanged();
+        return copy;
+    }
+}

src/main/java/net/dnorberg/rivencraft/menu/NotebookMenu.java

@@ -7,6 +7,7 @@ import net.dnorberg.rivencraft.registry.ModMenus;
 import net.dnorberg.rivencraft.writing.NotebookContents;
 import net.dnorberg.rivencraft.writing.PageContent;
 import net.dnorberg.rivencraft.item.PageItem;
+import net.dnorberg.rivencraft.item.CollationFolderItem;
 import net.minecraft.core.NonNullList;
 import net.minecraft.network.RegistryFriendlyByteBuf;
 import net.minecraft.world.Container;
@@ -28,6 +29,7 @@ public final class NotebookMenu extends AbstractContainerMenu {
     private final InteractionHand hand;
     private final int openedHotbarSlot;
     private final NotebookContainer contents;
+    private final int pageCapacity;
 
     public NotebookMenu(int containerId, Inventory inventory, RegistryFriendlyByteBuf data) {
         this(containerId, inventory, data.readBoolean() ? InteractionHand.OFF_HAND : InteractionHand.MAIN_HAND);
@@ -38,11 +40,12 @@ public final class NotebookMenu extends AbstractContainerMenu {
         this.playerInventory = inventory;
         this.hand = hand;
         this.openedHotbarSlot = inventory.selected;
+        this.pageCapacity = CollationFolderItem.capacity(inventory.player.getItemInHand(hand));
         this.contents = new NotebookContainer(inventory, hand);
 
         for (int page = 0; page < NOTEBOOK_SLOTS; page++) {
             // The client draws these pages on a filtered, scrollable surface instead.
-            addSlot(new PageSlot(contents, page, -1000, -1000));
+            addSlot(new PageSlot(contents, page, -1000, -1000, page < pageCapacity));
         }
         for (int row = 0; row < 3; row++) {
             for (int column = 0; column < 9; column++) {
@@ -61,11 +64,13 @@ public final class NotebookMenu extends AbstractContainerMenu {
                 : new Slot(playerInventory, inventoryIndex, x, y);
     }
 
+    public int pageCapacity() { return pageCapacity; }
+
     @Override
     public boolean stillValid(Player player) {
         return player.isAlive()
                 && (hand == InteractionHand.OFF_HAND || player.getInventory().selected == openedHotbarSlot)
-                && player.getItemInHand(hand).is(ModItems.NOTEBOOK.get());
+                && CollationFolderItem.isCollection(player.getItemInHand(hand));
     }
 
     @Override
@@ -108,7 +113,7 @@ public final class NotebookMenu extends AbstractContainerMenu {
         } else {
             return false;
         }
-        if (source < 0 || source >= NOTEBOOK_SLOTS || target < 0 || target >= NOTEBOOK_SLOTS
+        if (source < 0 || source >= pageCapacity || target < 0 || target >= pageCapacity
                 || contents.getItem(source).isEmpty()) {
             return false;
         }
@@ -132,14 +137,18 @@ public final class NotebookMenu extends AbstractContainerMenu {
     }
 
     private static final class PageSlot extends Slot {
-        private PageSlot(Container container, int slot, int x, int y) {
+        private final boolean enabled;
+
+        private PageSlot(Container container, int slot, int x, int y, boolean enabled) {
             super(container, slot, x, y);
+            this.enabled = enabled;
         }
 
         @Override public boolean mayPlace(ItemStack stack) {
-            return stack.is(ModItems.PAGE.get())
+            return enabled && stack.is(ModItems.PAGE.get())
                     && PageItem.content(stack).kind() != PageContent.Kind.LINK_PANEL;
         }
+        @Override public boolean mayPickup(Player player) { return enabled; }
         @Override public int getMaxStackSize() { return 1; }
     }
 
@@ -184,11 +193,12 @@ public final class NotebookMenu extends AbstractContainerMenu {
         public void setChanged() {
             super.setChanged();
             ItemStack notebook = inventory.player.getItemInHand(hand);
-            if (loading || !notebook.is(ModItems.NOTEBOOK.get())) {
+            if (loading || !CollationFolderItem.isCollection(notebook)) {
                 return;
             }
-            NonNullList<ItemStack> saved = NonNullList.withSize(NOTEBOOK_SLOTS, ItemStack.EMPTY);
-            for (int index = 0; index < NOTEBOOK_SLOTS; index++) {
+            int capacity = CollationFolderItem.capacity(notebook);
+            NonNullList<ItemStack> saved = NonNullList.withSize(capacity, ItemStack.EMPTY);
+            for (int index = 0; index < capacity; index++) {
                 ItemStack page = getItem(index);
                 saved.set(index, page.isEmpty() ? ItemStack.EMPTY : page.copyWithCount(1));
             }

src/main/java/net/dnorberg/rivencraft/menu/WritingDeskMenu.java

@@ -1,11 +1,13 @@
 package net.dnorberg.rivencraft.menu;
 
+import net.dnorberg.rivencraft.advancement.ProgressionAdvancements;
 import net.dnorberg.rivencraft.block.entity.WritingDeskBlockEntity;
 import net.dnorberg.rivencraft.item.PageItem;
 import net.dnorberg.rivencraft.registry.ModDataComponents;
 import net.dnorberg.rivencraft.registry.ModItems;
 import net.dnorberg.rivencraft.registry.ModMenus;
 import net.dnorberg.rivencraft.writing.NotebookContents;
+import net.dnorberg.rivencraft.item.CollationFolderItem;
 import net.dnorberg.rivencraft.writing.PageContent;
 import net.dnorberg.rivencraft.writing.SymbolCatalog;
 import net.dnorberg.rivencraft.writing.SymbolDisplayMetadata;
@@ -106,7 +108,7 @@ public final class WritingDeskMenu extends AbstractContainerMenu {
     public int pageCapacity(int collectionIndex) {
         if (collectionIndex < 0 || collectionIndex >= WritingDeskBlockEntity.COLLECTIONS) return 0;
         ItemStack collection = desk.getItem(collectionIndex);
-        return collection.is(ModItems.NOTEBOOK.get()) ? NotebookContents.MAX_PAGES
+        return CollationFolderItem.isCollection(collection) ? CollationFolderItem.capacity(collection)
                 : collection.is(ModItems.PAGE.get()) ? 1 : 0;
     }
     public List<SymbolDisplayMetadata> catalog() { return catalog; }
@@ -182,7 +184,8 @@ public final class WritingDeskMenu extends AbstractContainerMenu {
         ItemStack carried = getCarried();
         if (clientSide || !storablePage(carried)) return false;
         ItemStack collection = desk.getItem(collectionIndex);
-        if (collection.is(ModItems.NOTEBOOK.get())) {
+        if (CollationFolderItem.isCollection(collection)) {
+            if (pageIndex < 0 || pageIndex >= CollationFolderItem.capacity(collection)) return false;
             var pages = new java.util.ArrayList<>(collection.getOrDefault(
                     ModDataComponents.NOTEBOOK_CONTENTS.get(), NotebookContents.EMPTY).pages());
             while (pages.size() <= pageIndex) pages.add(ItemStack.EMPTY);
@@ -206,8 +209,10 @@ public final class WritingDeskMenu extends AbstractContainerMenu {
         if (!getCarried().isEmpty() || sourceCollection == targetCollection && sourcePage == targetPage) return false;
         ItemStack sourceBook = desk.getItem(sourceCollection);
         ItemStack targetBook = desk.getItem(targetCollection);
-        boolean sourceNotebook = sourceBook.is(ModItems.NOTEBOOK.get());
-        boolean targetNotebook = targetBook.is(ModItems.NOTEBOOK.get());
+        boolean sourceNotebook = CollationFolderItem.isCollection(sourceBook);
+        boolean targetNotebook = CollationFolderItem.isCollection(targetBook);
+        if (sourceNotebook && sourcePage >= CollationFolderItem.capacity(sourceBook)
+                || targetNotebook && targetPage >= CollationFolderItem.capacity(targetBook)) return false;
         if ((!sourceNotebook && (!sourceBook.is(ModItems.PAGE.get()) || sourcePage != 0))
                 || (!targetNotebook && (!targetBook.is(ModItems.PAGE.get()) || targetPage != 0))) return false;
         var sourcePages = sourceNotebook ? new java.util.ArrayList<>(sourceBook.getOrDefault(
@@ -246,7 +251,8 @@ public final class WritingDeskMenu extends AbstractContainerMenu {
     private boolean extractPage(int sourceCollection, int sourcePage, int targetSlot) {
         if (!getCarried().isEmpty() || targetSlot < -1 || targetSlot >= slots.size()) return false;
         ItemStack sourceBook = desk.getItem(sourceCollection);
-        boolean sourceNotebook = sourceBook.is(ModItems.NOTEBOOK.get());
+        boolean sourceNotebook = CollationFolderItem.isCollection(sourceBook);
+        if (sourceNotebook && sourcePage >= CollationFolderItem.capacity(sourceBook)) return false;
         if (!sourceNotebook && (!sourceBook.is(ModItems.PAGE.get()) || sourcePage != 0)) return false;
         var sourcePages = sourceNotebook ? new java.util.ArrayList<>(sourceBook.getOrDefault(
                 ModDataComponents.NOTEBOOK_CONTENTS.get(), NotebookContents.EMPTY).pages()) : null;
@@ -262,12 +268,12 @@ public final class WritingDeskMenu extends AbstractContainerMenu {
             Slot target = slots.get(targetSlot);
             if (!target.isActive() || !target.mayPlace(moving)) return false;
             ItemStack current = target.getItem();
-            if (targetSlot < WritingDeskBlockEntity.COLLECTIONS && current.is(ModItems.NOTEBOOK.get())) {
+            if (targetSlot < WritingDeskBlockEntity.COLLECTIONS && CollationFolderItem.isCollection(current)) {
                 var targetPages = targetSlot == sourceCollection ? sourcePages
                         : new java.util.ArrayList<>(current.getOrDefault(
                                 ModDataComponents.NOTEBOOK_CONTENTS.get(), NotebookContents.EMPTY).pages());
                 int position = -1;
-                for (int i = 0; i < NotebookContents.MAX_PAGES; i++) {
+                for (int i = 0; i < CollationFolderItem.capacity(current); i++) {
                     if (i >= targetPages.size() || targetPages.get(i).isEmpty()) {
                         position = i;
                         break;
@@ -317,7 +323,9 @@ public final class WritingDeskMenu extends AbstractContainerMenu {
             if (!moveItemStackTo(movingCopy, PLAYER_START, slots.size(), true) || !movingCopy.isEmpty()) {
                 return ItemStack.EMPTY;
             }
-            blockEntity.consumeCopyMaterials();
+            if (!blockEntity.consumeCopyMaterials()) return ItemStack.EMPTY;
+            if (player instanceof ServerPlayer serverPlayer)
+                ProgressionAdvancements.award(serverPlayer, ProgressionAdvancements.COPY_PAGE);
             refreshOutput();
             return copy;
         }
@@ -339,7 +347,7 @@ public final class WritingDeskMenu extends AbstractContainerMenu {
     private boolean moveIntoDesk(ItemStack moving) {
         if (moving.is(ModItems.INK_VIAL.get())) return moveItemStackTo(moving,
                 WritingDeskBlockEntity.INK, WritingDeskBlockEntity.INK + 1, false);
-        if (moving.is(ModItems.NOTEBOOK.get())) return moveItemStackTo(moving, firstVisibleTab, firstVisibleTab + VISIBLE_TABS, false);
+        if (CollationFolderItem.isCollection(moving)) return moveItemStackTo(moving, firstVisibleTab, firstVisibleTab + VISIBLE_TABS, false);
         if (moving.is(Items.PAPER))
             return moveItemStackTo(moving, WritingDeskBlockEntity.PAPER,
                     WritingDeskBlockEntity.PAPER + 1, false);
@@ -371,7 +379,8 @@ public final class WritingDeskMenu extends AbstractContainerMenu {
                 || pageIndex < 0 || pageIndex >= NotebookContents.MAX_PAGES) return ItemStack.EMPTY;
         ItemStack collection = desk.getItem(collectionIndex);
         if (collection.is(ModItems.PAGE.get())) return pageIndex == 0 ? collection : ItemStack.EMPTY;
-        if (collection.is(ModItems.NOTEBOOK.get())) {
+        if (CollationFolderItem.isCollection(collection)) {
+            if (pageIndex >= CollationFolderItem.capacity(collection)) return ItemStack.EMPTY;
             List<ItemStack> pages = collection.getOrDefault(
                     ModDataComponents.NOTEBOOK_CONTENTS.get(), NotebookContents.EMPTY).pages();
             return pageIndex < pages.size() ? pages.get(pageIndex) : ItemStack.EMPTY;
@@ -434,7 +443,11 @@ public final class WritingDeskMenu extends AbstractContainerMenu {
             return clientSide ? hasItem() : WritingDeskMenu.this.stillValid(player) && canCopy();
         }
         @Override public void onTake(Player player, ItemStack stack) {
-            if (!clientSide && blockEntity.consumeCopyMaterials()) refreshOutput();
+            if (!clientSide && blockEntity.consumeCopyMaterials()) {
+                if (player instanceof ServerPlayer serverPlayer)
+                    ProgressionAdvancements.award(serverPlayer, ProgressionAdvancements.COPY_PAGE);
+                refreshOutput();
+            }
             super.onTake(player, stack);
         }
     }

src/main/java/net/dnorberg/rivencraft/mixin/AgeDimensionSeedMixin.java

@@ -0,0 +1,24 @@
+package net.dnorberg.rivencraft.mixin;
+
+import dev.galacticraft.dynamicdimensions.impl.DynamicDimensionRegistryImpl;
+import net.dnorberg.rivencraft.book.AgeRegistrySavedData;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.level.Level;
+import net.minecraft.world.level.dimension.LevelStem;
+import net.minecraft.world.level.storage.WorldData;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.ModifyVariable;
+
+/** Give Dynamic Dimensions the saved Age seed before it constructs the level and its chunk RandomState. */
+@Mixin(value = DynamicDimensionRegistryImpl.class, remap = false)
+public abstract class AgeDimensionSeedMixin {
+    @ModifyVariable(method = "createDynamicLevel(Lnet/minecraft/resources/ResourceKey;Lnet/minecraft/world/level/storage/WorldData;Lnet/minecraft/world/level/dimension/LevelStem;Lnet/minecraft/server/level/ServerLevel;)Lnet/minecraft/server/level/ServerLevel;",
+            at = @At("STORE"), ordinal = 0, remap = false)
+    private long rivencraft$useSavedAgeSeed(long defaultSeed, ResourceKey<Level> dimension,
+                                            WorldData worldData, LevelStem stem, ServerLevel overworld) {
+        return AgeRegistrySavedData.get(overworld).findByDimension(dimension.location())
+                .map(age -> age.seed()).orElse(defaultSeed);
+    }
+}

src/main/java/net/dnorberg/rivencraft/mixin/LevelSkyBrightnessMixin.java

@@ -0,0 +1,40 @@
+package net.dnorberg.rivencraft.mixin;
+
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.book.AgeDimensionService;
+import net.dnorberg.rivencraft.book.AgeRegistrySavedData;
+import net.dnorberg.rivencraft.book.AgeSkyProfile;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.level.Level;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Shadow;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
+
+/** Combines multiple celestial light sources into Minecraft's one skylight channel. */
+@Mixin(Level.class)
+public abstract class LevelSkyBrightnessMixin {
+    @Shadow private int skyDarken;
+
+    @Inject(method = "updateSkyBrightness", at = @At("TAIL"))
+    private void rivencraft$stackCelestialLight(CallbackInfo callback) {
+        if (!((Object) this instanceof ServerLevel level) || !level.dimensionType().hasSkyLight()) return;
+        // ServerLevel updates sky brightness in its constructor, before the
+        // MinecraftServer has registered even the Overworld level. Only an
+        // established Rivencraft Age can have a saved celestial profile.
+        if (!level.dimension().location().getNamespace().equals(Rivencraft.MOD_ID)
+                || !level.dimension().location().getPath().startsWith("age/")
+                || level.getServer().overworld() == null) return;
+        AgeRegistrySavedData.get(level).definitions().stream()
+                .filter(age -> AgeDimensionService.dimensionKey(age).equals(level.dimension()))
+                .findFirst().ifPresent(age -> {
+                    AgeSkyProfile sky = AgeSkyProfile.forAge(age);
+                    if (sky.bodies().isEmpty()) return;
+                    float light = sky.lightAt(level.getDayTime());
+                    float weather = (1.0F - level.getRainLevel(1.0F) * 5.0F / 16.0F)
+                            * (1.0F - level.getThunderLevel(1.0F) * 5.0F / 16.0F);
+                    skyDarken = (int) ((1.0F - light * weather) * 11.0F);
+                });
+    }
+}

src/main/java/net/dnorberg/rivencraft/mixin/MobDropChanceAccessor.java

@@ -0,0 +1,12 @@
+package net.dnorberg.rivencraft.mixin;
+
+import net.minecraft.world.entity.EquipmentSlot;
+import net.minecraft.world.entity.Mob;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.gen.Invoker;
+
+@Mixin(Mob.class)
+public interface MobDropChanceAccessor {
+    @Invoker("getEquipmentDropChance")
+    float rivencraft$getEquipmentDropChance(EquipmentSlot slot);
+}

src/main/java/net/dnorberg/rivencraft/mixin/client/ClientLevelSkyColorMixin.java

@@ -0,0 +1,40 @@
+package net.dnorberg.rivencraft.mixin.client;
+
+import net.dnorberg.rivencraft.client.ClientAgeCelestialAngles;
+import net.dnorberg.rivencraft.book.AgeSkyProfile;
+import net.minecraft.client.multiplayer.ClientLevel;
+import net.minecraft.world.phys.Vec3;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfoReturnable;
+
+/** Keeps authored color pages visible in the sky without replacing vanilla sun and stars. */
+@Mixin(ClientLevel.class)
+public abstract class ClientLevelSkyColorMixin {
+    @Inject(method = "getSkyColor", at = @At("RETURN"), cancellable = true)
+    private void rivencraft$colorAuthoredSky(Vec3 position, float partialTick,
+                                             CallbackInfoReturnable<Vec3> result) {
+        ClientLevel level = (ClientLevel) (Object) this;
+        int color = ClientAgeCelestialAngles.skyColor(level.dimension());
+        if (color == -1 || ClientAgeCelestialAngles.staticSky(level.dimension())) return;
+        Vec3 natural = result.getReturnValue();
+        // Retain the vanilla day/night and precipitation darkening while replacing its hue.
+        AgeSkyProfile sky = ClientAgeCelestialAngles.sky(level.dimension());
+        double brightness = sky.bodies().isEmpty()
+                ? Math.max(natural.x, Math.max(natural.y, natural.z))
+                : Math.max(0.08D, sky.lightAt(level.getDayTime() + partialTick));
+        result.setReturnValue(Vec3.fromRGB24(color).scale(brightness));
+    }
+
+    @Inject(method = "getSkyDarken", at = @At("RETURN"), cancellable = true)
+    private void rivencraft$stackClientCelestialLight(float partialTick,
+                                                       CallbackInfoReturnable<Float> result) {
+        ClientLevel level = (ClientLevel) (Object) this;
+        AgeSkyProfile sky = ClientAgeCelestialAngles.sky(level.dimension());
+        if (sky.bodies().isEmpty() || !level.dimensionType().hasSkyLight()) return;
+        float weather = (1.0F - level.getRainLevel(partialTick) * 5.0F / 16.0F)
+                * (1.0F - level.getThunderLevel(partialTick) * 5.0F / 16.0F);
+        result.setReturnValue(0.2F + 0.8F * sky.lightAt(level.getDayTime() + partialTick) * weather);
+    }
+}

src/main/java/net/dnorberg/rivencraft/mixin/client/LevelRendererMixin.java

@@ -2,20 +2,37 @@ package net.dnorberg.rivencraft.mixin.client;
 
 import com.mojang.math.Axis;
 import net.dnorberg.rivencraft.client.ClientAgeCelestialAngles;
+import net.dnorberg.rivencraft.client.RivencraftSkyEffects;
+import net.minecraft.client.Camera;
 import net.minecraft.client.multiplayer.ClientLevel;
 import net.minecraft.client.renderer.LevelRenderer;
+import org.joml.Matrix4f;
 import org.joml.Quaternionf;
 import org.spongepowered.asm.mixin.Mixin;
 import org.spongepowered.asm.mixin.Shadow;
 import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
 import org.spongepowered.asm.mixin.injection.Redirect;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
 
 /** Rotates the vanilla sun, moon, and star path by each Age's saved angle. */
 @Mixin(LevelRenderer.class)
 public abstract class LevelRendererMixin {
+    private static final RivencraftSkyEffects RIVENCRAFT_SKY = new RivencraftSkyEffects();
+
     @Shadow
     private ClientLevel level;
 
+    @Inject(method = "renderSky", at = @At("HEAD"), cancellable = true)
+    private void rivencraft$renderAgeSky(Matrix4f frustumMatrix, Matrix4f projectionMatrix,
+                                        float partialTick, Camera camera, boolean isFoggy,
+                                        Runnable skyFogSetup, CallbackInfo callback) {
+        if (!level.dimension().location().getNamespace().equals("rivencraft")) return;
+        ClientAgeCelestialAngles.requestIfMissing(level.dimension());
+        if (RIVENCRAFT_SKY.renderSky(level, (int) level.getGameTime(), partialTick,
+                frustumMatrix, camera, projectionMatrix, isFoggy, skyFogSetup)) callback.cancel();
+    }
+
     @Redirect(
             method = "renderSky",
             at = @At(

src/main/java/net/dnorberg/rivencraft/network/AgeCelestialAnglePayload.java

@@ -1,6 +1,7 @@
 package net.dnorberg.rivencraft.network;
 
 import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.book.AgeSkyProfile;
 import net.minecraft.core.registries.Registries;
 import net.minecraft.network.RegistryFriendlyByteBuf;
 import net.minecraft.network.codec.StreamCodec;
@@ -9,8 +10,8 @@ import net.minecraft.resources.ResourceKey;
 import net.minecraft.resources.ResourceLocation;
 import net.minecraft.world.level.Level;
 
-/** Synchronizes an Age's saved celestial-plane rotation to clients. */
-public record AgeCelestialAnglePayload(ResourceKey<Level> dimension, float angle)
+/** Synchronizes an Age's saved celestial-plane rotation and authored sky to clients. */
+public record AgeCelestialAnglePayload(ResourceKey<Level> dimension, float angle, AgeSkyProfile sky)
         implements CustomPacketPayload {
     public static final Type<AgeCelestialAnglePayload> TYPE = new Type<>(
             ResourceLocation.fromNamespaceAndPath(Rivencraft.MOD_ID, "age_celestial_angle")
@@ -20,9 +21,34 @@ public record AgeCelestialAnglePayload(ResourceKey<Level> dimension, float angle
                     (buffer, payload) -> {
                         buffer.writeResourceKey(payload.dimension());
                         buffer.writeFloat(payload.angle());
+                        buffer.writeEnum(payload.sky().style());
+                        buffer.writeInt(payload.sky().color());
+                        buffer.writeVarInt(payload.sky().bodies().size());
+                        for (AgeSkyProfile.Body body : payload.sky().bodies()) {
+                            buffer.writeEnum(body.kind());
+                            buffer.writeInt(body.color());
+                            buffer.writeFloat(body.size());
+                            buffer.writeFloat(body.angle());
+                            buffer.writeDouble(body.period());
+                            buffer.writeFloat(body.phase());
+                            buffer.writeBoolean(body.clockwise());
+                        }
                     },
-                    buffer -> new AgeCelestialAnglePayload(
-                            buffer.readResourceKey(Registries.DIMENSION), buffer.readFloat())
+                    buffer -> {
+                        ResourceKey<Level> dimension = buffer.readResourceKey(Registries.DIMENSION);
+                        float angle = buffer.readFloat();
+                        AgeSkyProfile.Style style = buffer.readEnum(AgeSkyProfile.Style.class);
+                        int color = buffer.readInt();
+                        int count = buffer.readVarInt();
+                        if (count < 0 || count > 20) throw new IllegalArgumentException("Invalid celestial body count");
+                        java.util.List<AgeSkyProfile.Body> bodies = new java.util.ArrayList<>(count);
+                        for (int i = 0; i < count; i++) bodies.add(new AgeSkyProfile.Body(
+                                buffer.readEnum(AgeSkyProfile.Kind.class), buffer.readInt(),
+                                buffer.readFloat(), buffer.readFloat(), buffer.readDouble(), buffer.readFloat(),
+                                buffer.readBoolean()));
+                        return new AgeCelestialAnglePayload(dimension, angle,
+                                new AgeSkyProfile(style, color, bodies));
+                    }
             );
 
     @Override

src/main/java/net/dnorberg/rivencraft/network/ModNetworking.java

@@ -1,6 +1,7 @@
 package net.dnorberg.rivencraft.network;
 
 import net.dnorberg.rivencraft.book.LinkTarget;
+import net.dnorberg.rivencraft.book.LinkProperties;
 import net.dnorberg.rivencraft.book.LinkingService;
 import net.dnorberg.rivencraft.book.AgeReference;
 import net.dnorberg.rivencraft.book.AgeRegistrySavedData;
@@ -18,6 +19,7 @@ import net.dnorberg.rivencraft.event.AgeCelestialAngleSync;
 import net.dnorberg.rivencraft.item.DescriptiveBookItem;
 import net.dnorberg.rivencraft.item.LinkingBookItem;
 import net.dnorberg.rivencraft.menu.BookBinderMenu;
+import net.dnorberg.rivencraft.menu.LinkModifierMenu;
 import net.dnorberg.rivencraft.registry.ModDataComponents;
 import net.dnorberg.rivencraft.registry.ModItems;
 import net.dnorberg.rivencraft.writing.OrderedWriting;
@@ -59,7 +61,7 @@ public final class ModNetworking {
     }
 
     public static void register(RegisterPayloadHandlersEvent event) {
-        PayloadRegistrar registrar = event.registrar("15");
+        PayloadRegistrar registrar = event.registrar("18");
         registrar.playToServer(RequestDescriptiveBookScreenPayload.TYPE, RequestDescriptiveBookScreenPayload.STREAM_CODEC,
                 ModNetworking::requestDescriptiveBookScreen);
         registrar.playToClient(OpenDescriptiveBookScreenPayload.TYPE, OpenDescriptiveBookScreenPayload.STREAM_CODEC,
@@ -79,12 +81,28 @@ public final class ModNetworking {
                 ClientLinkPreviewHandler::handle);
         registrar.playToClient(AgeCelestialAnglePayload.TYPE, AgeCelestialAnglePayload.STREAM_CODEC,
                 ClientAgeCelestialAngles::handle);
+        registrar.playToServer(RequestAgeSkyPayload.TYPE, RequestAgeSkyPayload.STREAM_CODEC,
+                ModNetworking::requestAgeSky);
         registrar.playToClient(SereneAgeWhitelistPayload.TYPE, SereneAgeWhitelistPayload.STREAM_CODEC,
                 ClientSereneAgeWhitelist::handle);
         registrar.playToClient(WritingDeskCatalogPayload.TYPE, WritingDeskCatalogPayload.STREAM_CODEC,
                 ClientWritingDeskCatalog::handle);
         registrar.playToServer(SetBookBinderTitlePayload.TYPE, SetBookBinderTitlePayload.STREAM_CODEC,
                 ModNetworking::setBookBinderTitle);
+        registrar.playToServer(SetLinkModifierTitlePayload.TYPE, SetLinkModifierTitlePayload.STREAM_CODEC,
+                ModNetworking::setLinkModifierTitle);
+        registrar.playToServer(SetLinkModifierSeedPayload.TYPE, SetLinkModifierSeedPayload.STREAM_CODEC,
+                ModNetworking::setLinkModifierSeed);
+    }
+
+    private static void requestAgeSky(RequestAgeSkyPayload payload, IPayloadContext context) {
+        if (!(context.player() instanceof ServerPlayer player)) return;
+        // Portal renderers may request another Age. Only return registered Age data,
+        // never an arbitrary client-supplied dimension or generated terrain.
+        AgeRegistrySavedData.get(player.serverLevel()).definitions().stream()
+                .filter(age -> AgeDimensionService.dimensionKey(age).equals(payload.dimension()))
+                .findFirst()
+                .ifPresent(age -> AgeCelestialAngleSync.send(player, age));
     }
 
     private static void setBookBinderTitle(SetBookBinderTitlePayload payload, IPayloadContext context) {
@@ -95,6 +113,21 @@ public final class ModNetworking {
         }
     }
 
+    private static void setLinkModifierTitle(SetLinkModifierTitlePayload payload, IPayloadContext context) {
+        if (context.player() instanceof ServerPlayer player
+                && player.containerMenu instanceof LinkModifierMenu menu
+                && menu.containerId == payload.containerId()) {
+            menu.setTitle(player, payload.title());
+        }
+    }
+
+    private static void setLinkModifierSeed(SetLinkModifierSeedPayload payload, IPayloadContext context) {
+        if (context.player() instanceof ServerPlayer player
+                && player.containerMenu instanceof LinkModifierMenu menu
+                && menu.containerId == payload.containerId())
+            menu.setSeed(player, payload.seed());
+    }
+
     private static void requestDescriptiveBookScreen(RequestDescriptiveBookScreenPayload payload, IPayloadContext context) {
         if (!(context.player() instanceof ServerPlayer player)) {
             return;
@@ -163,7 +196,9 @@ public final class ModNetworking {
         try {
             AgeReference reference = new AgeReference(UUID.randomUUID(), title);
             if (AgeDimensionService.resolve(player, reference, access.stack()
-                    .getOrDefault(ModDataComponents.BOOK_WRITING.get(), OrderedWriting.EMPTY)).isEmpty()) {
+                    .getOrDefault(ModDataComponents.BOOK_WRITING.get(), OrderedWriting.EMPTY),
+                    !access.stack().getOrDefault(ModDataComponents.LINK_PROPERTIES.get(), LinkProperties.NONE)
+                            .has(LinkProperties.DISABLE_PLATFORM)).isEmpty()) {
                 player.displayClientMessage(Component.translatable("message.rivencraft.descriptive_book.unavailable"), true);
                 return;
             }
@@ -211,7 +246,7 @@ public final class ModNetworking {
 
         ItemStack stack = player.getItemInHand(hand(payload.offhand()));
         if (stack.is(ModItems.LINKING_BOOK.get()) && stack.has(ModDataComponents.LINK_TARGET.get())) {
-            LinkingBookItem.useBoundBook(player, stack);
+            LinkingBookItem.useHandheldBook(player, hand(payload.offhand()));
         }
     }
 
@@ -245,7 +280,8 @@ public final class ModNetworking {
         }
 
         if (stack.is(ModItems.DESCRIPTIVE_BOOK.get())) {
-            DescriptiveBookItem.useWrittenBook(player, stack);
+            if (payload.fromStand()) DescriptiveBookItem.useWrittenBook(player, stack);
+            else DescriptiveBookItem.useHandheldBook(player, hand(payload.offhand()));
         }
     }
 
@@ -268,7 +304,9 @@ public final class ModNetworking {
         LinkTarget target;
         if (payload.descriptiveBook() && stack.is(ModItems.DESCRIPTIVE_BOOK.get())) {
             AgeReference age = stack.get(ModDataComponents.AGE_REFERENCE.get());
-            target = age == null ? null : AgeDimensionService.resolve(player, age).orElse(null);
+            target = age == null ? null : AgeDimensionService.resolve(player, age, OrderedWriting.EMPTY,
+                    !stack.getOrDefault(ModDataComponents.LINK_PROPERTIES.get(), LinkProperties.NONE)
+                            .has(LinkProperties.DISABLE_PLATFORM)).orElse(null);
         } else if (!payload.descriptiveBook() && stack.is(ModItems.LINKING_BOOK.get())) {
             target = stack.get(ModDataComponents.LINK_TARGET.get());
         } else {
@@ -322,8 +360,7 @@ public final class ModNetworking {
 
     /** Sky effects, not dimension IDs, decide the backdrop for custom Ages. */
     private static int previewSkyColor(ServerLevel level, BlockPos origin) {
-        return AgeEnvironmentCompiler.previewSkyColor(level.dimensionType().effectsLocation(),
-                level.getBiome(origin).value().getSkyColor());
+        return AgeEnvironmentCompiler.previewSkyColor(level, origin);
     }
 
     private static InteractionHand hand(boolean offhand) {

src/main/java/net/dnorberg/rivencraft/network/RequestAgeSkyPayload.java

@@ -0,0 +1,24 @@
+package net.dnorberg.rivencraft.network;
+
+import net.dnorberg.rivencraft.Rivencraft;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.network.RegistryFriendlyByteBuf;
+import net.minecraft.network.codec.StreamCodec;
+import net.minecraft.network.protocol.common.custom.CustomPacketPayload;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.resources.ResourceLocation;
+import net.minecraft.world.level.Level;
+
+/** Requests the saved sky profile when a renderer reaches an Age before dimension-change sync. */
+public record RequestAgeSkyPayload(ResourceKey<Level> dimension) implements CustomPacketPayload {
+    public static final Type<RequestAgeSkyPayload> TYPE = new Type<>(
+            ResourceLocation.fromNamespaceAndPath(Rivencraft.MOD_ID, "request_age_sky"));
+    public static final StreamCodec<RegistryFriendlyByteBuf, RequestAgeSkyPayload> STREAM_CODEC = StreamCodec.of(
+            (buffer, payload) -> buffer.writeResourceKey(payload.dimension()),
+            buffer -> new RequestAgeSkyPayload(buffer.readResourceKey(Registries.DIMENSION)));
+
+    @Override
+    public Type<? extends CustomPacketPayload> type() {
+        return TYPE;
+    }
+}

src/main/java/net/dnorberg/rivencraft/network/SetLinkModifierSeedPayload.java

@@ -0,0 +1,19 @@
+package net.dnorberg.rivencraft.network;
+
+import net.dnorberg.rivencraft.Rivencraft;
+import net.minecraft.network.RegistryFriendlyByteBuf;
+import net.minecraft.network.codec.ByteBufCodecs;
+import net.minecraft.network.codec.StreamCodec;
+import net.minecraft.network.protocol.common.custom.CustomPacketPayload;
+import net.minecraft.resources.ResourceLocation;
+
+public record SetLinkModifierSeedPayload(int containerId, String seed) implements CustomPacketPayload {
+    public static final Type<SetLinkModifierSeedPayload> TYPE = new Type<>(
+            ResourceLocation.fromNamespaceAndPath(Rivencraft.MOD_ID, "set_link_modifier_seed"));
+    public static final StreamCodec<RegistryFriendlyByteBuf, SetLinkModifierSeedPayload> STREAM_CODEC =
+            StreamCodec.composite(ByteBufCodecs.VAR_INT, SetLinkModifierSeedPayload::containerId,
+                    ByteBufCodecs.STRING_UTF8, SetLinkModifierSeedPayload::seed,
+                    SetLinkModifierSeedPayload::new);
+
+    @Override public Type<? extends CustomPacketPayload> type() { return TYPE; }
+}

src/main/java/net/dnorberg/rivencraft/network/SetLinkModifierTitlePayload.java

@@ -0,0 +1,19 @@
+package net.dnorberg.rivencraft.network;
+
+import net.dnorberg.rivencraft.Rivencraft;
+import net.minecraft.network.RegistryFriendlyByteBuf;
+import net.minecraft.network.codec.ByteBufCodecs;
+import net.minecraft.network.codec.StreamCodec;
+import net.minecraft.network.protocol.common.custom.CustomPacketPayload;
+import net.minecraft.resources.ResourceLocation;
+
+public record SetLinkModifierTitlePayload(int containerId, String title) implements CustomPacketPayload {
+    public static final Type<SetLinkModifierTitlePayload> TYPE = new Type<>(
+            ResourceLocation.fromNamespaceAndPath(Rivencraft.MOD_ID, "set_link_modifier_title"));
+    public static final StreamCodec<RegistryFriendlyByteBuf, SetLinkModifierTitlePayload> STREAM_CODEC =
+            StreamCodec.composite(ByteBufCodecs.VAR_INT, SetLinkModifierTitlePayload::containerId,
+                    ByteBufCodecs.STRING_UTF8, SetLinkModifierTitlePayload::title,
+                    SetLinkModifierTitlePayload::new);
+
+    @Override public Type<? extends CustomPacketPayload> type() { return TYPE; }
+}

src/main/java/net/dnorberg/rivencraft/portal/CrystalPortalNetwork.java

@@ -14,8 +14,12 @@ import net.dnorberg.rivencraft.registry.ModBlocks;
 import net.minecraft.core.BlockPos;
 import net.minecraft.core.Direction;
 import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.entity.Entity;
 import net.minecraft.world.level.block.Blocks;
 import net.minecraft.world.level.block.state.BlockState;
+import net.neoforged.neoforge.common.NeoForge;
+import net.neoforged.neoforge.common.util.BlockSnapshot;
+import net.neoforged.neoforge.event.level.BlockEvent;
 
 /** Bounded, loaded-chunk-only adaptation of Legacy's crystal network flood. */
 public final class CrystalPortalNetwork {
@@ -32,14 +36,22 @@ public final class CrystalPortalNetwork {
 
     private CrystalPortalNetwork() {}
 
-    public record Plan(List<BlockPos> portalCells) {
+    public record Plan(List<BlockPos> portalCells, boolean waitingForChunks) {
+        public Plan(List<BlockPos> portalCells) { this(portalCells, false); }
         public boolean valid() { return !portalCells.isEmpty(); }
     }
 
+    public enum CellStatus { VALID, INVALID, WAITING_FOR_CHUNKS }
+
     public static Plan plan(ServerLevel level, BlockPos receptacle) {
+        return plan(level, receptacle, false);
+    }
+
+    private static Plan plan(ServerLevel level, BlockPos receptacle, boolean allowUnownedCells) {
         BlockState holder = level.getBlockState(receptacle);
         if (!holder.is(ModBlocks.BOOK_RECEPTACLE.get())) return new Plan(List.of());
         BlockPos base = receptacle.relative(holder.getValue(BookReceptacleBlock.FACING).getOpposite());
+        if (!level.hasChunkAt(base)) return new Plan(List.of(), true);
         if (!level.getBlockState(base).is(ModBlocks.CRYSTAL_BLOCK.get())) return new Plan(List.of());
 
         Set<BlockPos> crystals = new HashSet<>();
@@ -48,7 +60,7 @@ public final class CrystalPortalNetwork {
         while (!pendingCrystals.isEmpty()) {
             BlockPos pos = pendingCrystals.removeFirst();
             if (!within(base, pos) || !level.isInWorldBounds(pos)) continue;
-            if (!level.hasChunkAt(pos)) return new Plan(List.of());
+            if (!level.hasChunkAt(pos)) return new Plan(List.of(), true);
             if (!level.getBlockState(pos).is(ModBlocks.CRYSTAL_BLOCK.get()) || !crystals.add(pos)) continue;
             if (atBoundary(base, pos)) return new Plan(List.of());
             if (crystals.size() > MAX_CRYSTALS) return new Plan(List.of());
@@ -62,8 +74,9 @@ public final class CrystalPortalNetwork {
         while (!candidates.isEmpty()) {
             BlockPos pos = candidates.removeFirst();
             queued.remove(pos);
-            if (!level.isInWorldBounds(pos) || !level.hasChunkAt(pos)) return new Plan(List.of());
-            if (portals.contains(pos) || !mayFill(level, pos, receptacle)) continue;
+            if (!level.isInWorldBounds(pos)) return new Plan(List.of());
+            if (!level.hasChunkAt(pos)) return new Plan(List.of(), true);
+            if (portals.contains(pos) || !mayFill(level, pos, receptacle, allowUnownedCells)) continue;
             if (adjacentCount(pos, crystals, portals) < 2) continue;
             portals.add(pos);
             if (portals.size() > MAX_PORTALS) return new Plan(List.of());
@@ -97,6 +110,28 @@ public final class CrystalPortalNetwork {
     }
 
     public static boolean activate(ServerLevel level, BlockPos receptacle, Plan plan) {
+        return activate(level, receptacle, plan, null);
+    }
+
+    /** Repairs only existing, framed cells whose owner pointer was lost by an older live-view update. */
+    public static boolean recoverSavedOwners(ServerLevel level, BlockPos receptacle) {
+        if (!(level.getBlockEntity(receptacle) instanceof BookReceptacleBlockEntity holder)
+                || holder.getBook().isEmpty()) return false;
+        Plan plan = plan(level, receptacle, true);
+        if (!plan.valid()) return false;
+        for (BlockPos pos : plan.portalCells()) {
+            if (!(level.getBlockEntity(pos) instanceof CrystalPortalBlockEntity portal)
+                    || portal.receptacle() != null && !receptacle.equals(portal.receptacle())) return false;
+        }
+        for (BlockPos pos : plan.portalCells()) {
+            CrystalPortalBlockEntity portal = (CrystalPortalBlockEntity) level.getBlockEntity(pos);
+            if (portal.receptacle() == null) portal.setReceptacle(receptacle);
+        }
+        return true;
+    }
+
+    /** The player who inserted the book owns each newly placed portal cell for claim checks. */
+    public static boolean activate(ServerLevel level, BlockPos receptacle, Plan plan, Entity actor) {
         if (!plan.valid() || !(level.getBlockEntity(receptacle) instanceof BookReceptacleBlockEntity holder)
                 || holder.getBook().isEmpty()) return false;
         List<BlockPos> placed = new ArrayList<>();
@@ -106,28 +141,39 @@ public final class CrystalPortalNetwork {
                 return false;
             }
             if (level.getBlockState(pos).isAir()) {
-                if (!level.setBlock(pos, ModBlocks.CRYSTAL_PORTAL.get().defaultBlockState(), 3)) {
+                BlockSnapshot snapshot = actor == null ? null : BlockSnapshot.create(level.dimension(), level, pos);
+                BlockState prior = level.getBlockState(pos);
+                // Defer neighbor notifications until the entire opening exists.
+                // Otherwise the first cells see an incomplete brace and the
+                // portal's neighbor validator removes them during activation.
+                if (!level.setBlock(pos, ModBlocks.CRYSTAL_PORTAL.get().defaultBlockState(), 2)) {
                     rollback(level, placed);
                     return false;
                 }
+                if (snapshot != null) {
+                    var event = new BlockEvent.EntityPlaceEvent(snapshot, prior, actor);
+                    NeoForge.EVENT_BUS.post(event);
+                    if (event.isCanceled()) {
+                        snapshot.restore();
+                        rollback(level, placed);
+                        return false;
+                    }
+                }
                 placed.add(pos);
             }
             if (level.getBlockEntity(pos) instanceof CrystalPortalBlockEntity portal) {
                 portal.setReceptacle(receptacle);
-                level.scheduleTick(pos, ModBlocks.CRYSTAL_PORTAL.get(), 40);
             } else {
                 rollback(level, placed);
                 return false;
             }
         }
-        // All cells are now present, so the same bracing rule used for the
-        // Immersive Portals surface can orient the two-sided fallback model.
-        for (CrystalPortalSurfaces.Surface surface : CrystalPortalSurfaces.group(level, plan)) {
-            for (BlockPos pos : surface.cells()) {
-                BlockState state = level.getBlockState(pos);
-                Direction.Axis axis = surface.normal().getAxis();
-                if (state.getValue(CrystalPortalBlock.AXIS) != axis)
-                    level.setBlock(pos, state.setValue(CrystalPortalBlock.AXIS, axis), 2);
+        orientSurfaces(level, plan);
+        for (BlockPos pos : plan.portalCells()) {
+            if (!(level.getBlockEntity(pos) instanceof CrystalPortalBlockEntity portal)
+                    || !receptacle.equals(portal.receptacle())) {
+                rollback(level, placed);
+                return false;
             }
         }
         return true;
@@ -148,13 +194,24 @@ public final class CrystalPortalNetwork {
     }
 
     /** One bounded repair pass per receptacle, rather than a full flood per portal cell. */
-    public static void reconcile(ServerLevel level, BlockPos receptacle) {
+    public static boolean reconcile(ServerLevel level, BlockPos receptacle) {
         Plan plan = plan(level, receptacle);
         if (!plan.valid()) {
-            shutdown(level, receptacle);
-            return;
+            // Neighboring chunks can still be loading when the receptacle first
+            // ticks after a restart. An incomplete view is not a broken frame.
+            if (!plan.waitingForChunks()) shutdown(level, receptacle);
+            return false;
         }
         Set<BlockPos> wanted = new HashSet<>(plan.portalCells());
+        // A background pass must not create blocks without the owner present:
+        // that would bypass the placement/protection event used at activation.
+        for (BlockPos pos : wanted) {
+            if (!(level.getBlockEntity(pos) instanceof CrystalPortalBlockEntity portal)
+                    || !receptacle.equals(portal.receptacle())) {
+                shutdown(level, receptacle);
+                return false;
+            }
+        }
         for (BlockPos pos : BlockPos.betweenClosed(receptacle.offset(-CLEANUP_RADIUS, -CLEANUP_RADIUS, -CLEANUP_RADIUS),
                 receptacle.offset(CLEANUP_RADIUS, CLEANUP_RADIUS, CLEANUP_RADIUS))) {
             if (!level.hasChunkAt(pos)) continue;
@@ -162,29 +219,64 @@ public final class CrystalPortalNetwork {
                     && receptacle.equals(portal.receptacle()) && !wanted.contains(pos))
                 level.setBlock(pos, Blocks.AIR.defaultBlockState(), 3);
         }
-        activate(level, receptacle, plan);
+        orientSurfaces(level, plan);
+        return true;
     }
 
-    public static boolean validCell(ServerLevel level, BlockPos pos, BlockPos receptacle) {
+    private static void orientSurfaces(ServerLevel level, Plan plan) {
+        for (CrystalPortalSurfaces.Surface surface : CrystalPortalSurfaces.group(level, plan)) {
+            for (BlockPos pos : surface.cells()) {
+                BlockState state = level.getBlockState(pos);
+                Direction.Axis axis = surface.normal().getAxis();
+                if (state.getValue(CrystalPortalBlock.AXIS) != axis)
+                    updatePortalState(level, pos, state.setValue(CrystalPortalBlock.AXIS, axis));
+            }
+        }
+    }
+
+    /** The vanilla-style surface remains visible until its optional live view is ready. */
+    public static void setLiveView(ServerLevel level, Plan plan, boolean live) {
+        for (BlockPos pos : plan.portalCells()) {
+            BlockState state = level.getBlockState(pos);
+            if (state.is(ModBlocks.CRYSTAL_PORTAL.get()) && state.getValue(CrystalPortalBlock.LIVE_VIEW) != live)
+                updatePortalState(level, pos, state.setValue(CrystalPortalBlock.LIVE_VIEW, live));
+        }
+    }
+
+    private static void updatePortalState(ServerLevel level, BlockPos pos, BlockState replacement) {
+        BlockPos owner = level.getBlockEntity(pos) instanceof CrystalPortalBlockEntity portal
+                ? portal.receptacle() : null;
+        if (!level.setBlock(pos, replacement, 2) || owner == null) return;
+        if (level.getBlockEntity(pos) instanceof CrystalPortalBlockEntity portal
+                && !owner.equals(portal.receptacle())) portal.setReceptacle(owner);
+    }
+
+    public static CellStatus cellStatus(ServerLevel level, BlockPos pos, BlockPos receptacle) {
         if (Math.abs(receptacle.getX() - pos.getX()) > CLEANUP_RADIUS
                 || Math.abs(receptacle.getY() - pos.getY()) > CLEANUP_RADIUS
-                || Math.abs(receptacle.getZ() - pos.getZ()) > CLEANUP_RADIUS
-                || !level.hasChunkAt(receptacle)
-                || !(level.getBlockEntity(receptacle) instanceof BookReceptacleBlockEntity holder)
-                || holder.getBook().isEmpty()) return false;
+                || Math.abs(receptacle.getZ() - pos.getZ()) > CLEANUP_RADIUS) return CellStatus.INVALID;
+        if (!level.hasChunkAt(receptacle)) return CellStatus.WAITING_FOR_CHUNKS;
         BlockState state = level.getBlockState(receptacle);
-        if (!state.is(ModBlocks.BOOK_RECEPTACLE.get()) || !level.getBlockState(receptacle.relative(
-                state.getValue(BookReceptacleBlock.FACING).getOpposite())).is(ModBlocks.CRYSTAL_BLOCK.get()))
-            return false;
+        if (!state.is(ModBlocks.BOOK_RECEPTACLE.get())) return CellStatus.INVALID;
+        BlockPos base = receptacle.relative(state.getValue(BookReceptacleBlock.FACING).getOpposite());
+        if (!level.hasChunkAt(base)) return CellStatus.WAITING_FOR_CHUNKS;
+        if (!level.getBlockState(base).is(ModBlocks.CRYSTAL_BLOCK.get())) return CellStatus.INVALID;
+        if (!(level.getBlockEntity(receptacle) instanceof BookReceptacleBlockEntity holder))
+            return CellStatus.WAITING_FOR_CHUNKS;
+        if (holder.getBook().isEmpty()) return CellStatus.INVALID;
+        // A neighboring chunk may hold one of the braces. Do not tear down a
+        // persisted portal until all six neighbors are available to inspect.
+        for (Direction direction : Direction.values())
+            if (!level.hasChunkAt(pos.relative(direction))) return CellStatus.WAITING_FOR_CHUNKS;
         for (Direction.Axis axis : Direction.Axis.values()) {
             // Quick tension check before the bounded network/path revalidation.
             if (!axisBraced(level, pos, axis)) continue;
             int other = 0;
             for (Direction.Axis alternative : Direction.Axis.values())
                 if (alternative != axis && axisBraced(level, pos, alternative)) other++;
-            if (other > 0) return true;
+            if (other > 0) return CellStatus.VALID;
         }
-        return false;
+        return CellStatus.INVALID;
     }
 
     private static boolean axisBraced(ServerLevel level, BlockPos pos, Direction.Axis axis) {
@@ -205,11 +297,15 @@ public final class CrystalPortalNetwork {
     }
 
     private static boolean mayFill(ServerLevel level, BlockPos pos, BlockPos receptacle) {
+        return mayFill(level, pos, receptacle, false);
+    }
+
+    private static boolean mayFill(ServerLevel level, BlockPos pos, BlockPos receptacle, boolean allowUnowned) {
         if (!level.hasChunkAt(pos) || !level.isInWorldBounds(pos)) return false;
         BlockState state = level.getBlockState(pos);
         return state.isAir() || state.is(ModBlocks.CRYSTAL_PORTAL.get())
                 && level.getBlockEntity(pos) instanceof CrystalPortalBlockEntity portal
-                && receptacle.equals(portal.receptacle());
+                && (receptacle.equals(portal.receptacle()) || allowUnowned && portal.receptacle() == null);
     }
 
     private static int adjacentCount(BlockPos pos, Set<BlockPos> crystals, Set<BlockPos> portals) {

src/main/java/net/dnorberg/rivencraft/portal/PortalTravelCooldown.java

@@ -1,12 +1,34 @@
 package net.dnorberg.rivencraft.portal;
 
-/** Server tick counters restart with the process; old saved values cannot block new sessions. */
+import java.util.Map;
+import java.util.WeakHashMap;
+import net.minecraft.world.entity.Entity;
+import net.minecraft.server.level.ServerPlayer;
+
+/** Session-only portal cooldowns: tick counters must never be saved with players. */
 public final class PortalTravelCooldown {
     public static final long TICKS = 40;
+    private static final Map<Entity, Long> LAST_USE = new WeakHashMap<>();
 
     private PortalTravelCooldown() {}
 
     public static boolean blocked(long now, long previous) {
         return previous >= 0 && now >= previous && now - previous < TICKS;
     }
+
+    public static boolean blocked(Entity entity, long now) {
+        return blocked(now, LAST_USE.getOrDefault(entity, -1L));
+    }
+
+    public static void mark(Entity entity, long now) {
+        LAST_USE.put(entity, now);
+    }
+
+    public static void forget(Entity entity) {
+        LAST_USE.remove(entity);
+    }
+
+    public static void clear() {
+        LAST_USE.clear();
+    }
 }

src/main/java/net/dnorberg/rivencraft/portal/PortalTravelQueue.java

@@ -0,0 +1,97 @@
+package net.dnorberg.rivencraft.portal;
+
+import java.util.ArrayList;
+import java.util.IdentityHashMap;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+import net.dnorberg.rivencraft.block.entity.BookReceptacleBlockEntity;
+import net.dnorberg.rivencraft.block.entity.CrystalPortalBlockEntity;
+import net.dnorberg.rivencraft.book.AgeDimensionService;
+import net.dnorberg.rivencraft.book.AgeReference;
+import net.dnorberg.rivencraft.book.LinkDisarmService;
+import net.dnorberg.rivencraft.book.LinkProperties;
+import net.dnorberg.rivencraft.book.LinkTarget;
+import net.dnorberg.rivencraft.book.LinkingService;
+import net.dnorberg.rivencraft.item.DescriptiveBookItem;
+import net.dnorberg.rivencraft.item.LinkingBookItem;
+import net.dnorberg.rivencraft.registry.ModDataComponents;
+import net.dnorberg.rivencraft.registry.ModItems;
+import net.dnorberg.rivencraft.writing.OrderedWriting;
+import net.minecraft.core.BlockPos;
+import net.minecraft.server.MinecraftServer;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.world.entity.Entity;
+import net.minecraft.world.item.ItemStack;
+
+/** Defers block-collision travel until the movement packet that entered the portal has finished. */
+public final class PortalTravelQueue {
+    private static final Map<Entity, Pending> PENDING = new IdentityHashMap<>();
+
+    private record Pending(ServerLevel source, BlockPos portal, BlockPos receptacle,
+                           ItemStack book, long queuedTick) {}
+    private record Travel(Entity entity, Pending pending) {}
+
+    private PortalTravelQueue() {}
+
+    public static void enqueue(Entity entity, ServerLevel source, BlockPos portal,
+                               BlockPos receptacle, ItemStack book, long now) {
+        PENDING.putIfAbsent(entity, new Pending(source, portal.immutable(), receptacle.immutable(),
+                book.copyWithCount(1), now));
+    }
+
+    public static void process(MinecraftServer server) {
+        List<Travel> ready = new ArrayList<>();
+        Iterator<Map.Entry<Entity, Pending>> iterator = PENDING.entrySet().iterator();
+        while (iterator.hasNext()) {
+            var entry = iterator.next();
+            if (server.getTickCount() <= entry.getValue().queuedTick()) continue;
+            ready.add(new Travel(entry.getKey(), entry.getValue()));
+            iterator.remove();
+        }
+        // Travel can itself cause block-collision callbacks, so do not keep an
+        // iterator over the pending map while changing the player's dimension.
+        for (Travel travel : ready) {
+            Entity entity = travel.entity();
+            Pending pending = travel.pending();
+            if ((entity instanceof ServerPlayer player
+                    && server.getPlayerList().getPlayer(player.getUUID()) != player)
+                    || entity.isRemoved() || !entity.isAlive() || entity.level() != pending.source()
+                    || !(pending.source().getBlockEntity(pending.portal()) instanceof CrystalPortalBlockEntity portal)
+                    || !pending.receptacle().equals(portal.receptacle())
+                    || !(pending.source().getBlockEntity(pending.receptacle()) instanceof BookReceptacleBlockEntity holder)
+                    || !ItemStack.isSameItemSameComponents(holder.getBook(), pending.book())) continue;
+            if (entity instanceof ServerPlayer player) {
+                if (pending.book().is(ModItems.LINKING_BOOK.get()))
+                    LinkingBookItem.usePortalBook(player, pending.book());
+                else if (pending.book().is(ModItems.DESCRIPTIVE_BOOK.get()))
+                    DescriptiveBookItem.usePortalBook(player, pending.book());
+            } else {
+                travelEntity(entity, pending);
+            }
+        }
+    }
+
+    private static void travelEntity(Entity entity, Pending pending) {
+        ItemStack book = pending.book();
+        LinkProperties properties = book.getOrDefault(ModDataComponents.LINK_PROPERTIES.get(), LinkProperties.NONE);
+        if (properties.has(LinkProperties.DISARM) && !LinkDisarmService.mayTravel(entity)) return;
+        LinkTarget target;
+        boolean descriptive = book.is(ModItems.DESCRIPTIVE_BOOK.get());
+        if (descriptive) {
+            AgeReference reference = book.get(ModDataComponents.AGE_REFERENCE.get());
+            if (reference == null) return;
+            properties = properties.forDescriptiveBook();
+            target = AgeDimensionService.resolve(pending.source(), reference, OrderedWriting.EMPTY,
+                    !properties.has(LinkProperties.DISABLE_PLATFORM)).orElse(null);
+        } else if (book.is(ModItems.LINKING_BOOK.get())) {
+            target = book.get(ModDataComponents.LINK_TARGET.get());
+        } else return;
+        if (target == null) return;
+        LinkingService.travelEntityPortal(entity, target, properties, descriptive);
+    }
+
+    public static void forget(ServerPlayer player) { PENDING.remove(player); }
+    public static void clear() { PENDING.clear(); }
+}

src/main/java/net/dnorberg/rivencraft/registry/ModBlockEntities.java

@@ -5,6 +5,7 @@ import net.dnorberg.rivencraft.block.entity.BookStandBlockEntity;
 import net.dnorberg.rivencraft.block.entity.BookBinderBlockEntity;
 import net.dnorberg.rivencraft.block.entity.WritingDeskBlockEntity;
 import net.dnorberg.rivencraft.block.entity.InkMixerBlockEntity;
+import net.dnorberg.rivencraft.block.entity.LinkModifierBlockEntity;
 import net.dnorberg.rivencraft.block.entity.StarFissureBlockEntity;
 import net.dnorberg.rivencraft.block.entity.BookReceptacleBlockEntity;
 import net.dnorberg.rivencraft.block.entity.CrystalPortalBlockEntity;
@@ -31,6 +32,9 @@ public final class ModBlockEntities {
     public static final DeferredHolder<BlockEntityType<?>, BlockEntityType<InkMixerBlockEntity>> INK_MIXER =
             BLOCK_ENTITIES.register("ink_mixer", () -> BlockEntityType.Builder
                     .of(InkMixerBlockEntity::new, ModBlocks.INK_MIXER.get()).build(null));
+    public static final DeferredHolder<BlockEntityType<?>, BlockEntityType<LinkModifierBlockEntity>> LINK_MODIFIER =
+            BLOCK_ENTITIES.register("link_modifier", () -> BlockEntityType.Builder
+                    .of(LinkModifierBlockEntity::new, ModBlocks.LINK_MODIFIER.get()).build(null));
     public static final DeferredHolder<BlockEntityType<?>, BlockEntityType<StarFissureBlockEntity>> STAR_FISSURE =
             BLOCK_ENTITIES.register("star_fissure", () -> BlockEntityType.Builder
                     .of(StarFissureBlockEntity::new, ModBlocks.STAR_FISSURE.get()).build(null));

src/main/java/net/dnorberg/rivencraft/registry/ModBlocks.java

@@ -5,6 +5,7 @@ import net.dnorberg.rivencraft.block.BookStandBlock;
 import net.dnorberg.rivencraft.block.BookBinderBlock;
 import net.dnorberg.rivencraft.block.WritingDeskBlock;
 import net.dnorberg.rivencraft.block.InkMixerBlock;
+import net.dnorberg.rivencraft.block.LinkModifierBlock;
 import net.dnorberg.rivencraft.block.BuddingCrystalBlock;
 import net.dnorberg.rivencraft.block.StarFissureBlock;
 import net.dnorberg.rivencraft.block.DecayBlock;
@@ -40,6 +41,9 @@ public final class ModBlocks {
             "ink_mixer", InkMixerBlock::new,
             BlockBehaviour.Properties.ofFullCopy(Blocks.CRAFTING_TABLE).noOcclusion()
     );
+    public static final DeferredBlock<LinkModifierBlock> LINK_MODIFIER = BLOCKS.registerBlock(
+            "link_modifier", LinkModifierBlock::new,
+            BlockBehaviour.Properties.ofFullCopy(Blocks.CRAFTING_TABLE).noOcclusion());
     public static final DeferredBlock<Block> CRYSTAL_BLOCK = BLOCKS.registerBlock("crystal_block",
             Block::new, BlockBehaviour.Properties.ofFullCopy(Blocks.AMETHYST_BLOCK).mapColor(MapColor.COLOR_BLUE));
     public static final DeferredBlock<BookReceptacleBlock> BOOK_RECEPTACLE = BLOCKS.registerBlock("book_receptacle",
@@ -70,8 +74,8 @@ public final class ModBlocks {
             DecayBlock::new, BlockBehaviour.Properties.ofFullCopy(Blocks.STONE)
                     .strength(5.0F, 10.0F).noLootTable());
     public static final DeferredBlock<CloudPlatformBlock> CLOUD_PLATFORM = BLOCKS.registerBlock("cloud_platform",
-            CloudPlatformBlock::new, BlockBehaviour.Properties.ofFullCopy(Blocks.WHITE_STAINED_GLASS)
-                    .strength(1.5F).noOcclusion().noLootTable());
+            CloudPlatformBlock::new, BlockBehaviour.Properties.ofFullCopy(Blocks.AMETHYST_BLOCK)
+                    .mapColor(MapColor.COLOR_BLUE).strength(0.3F).noLootTable());
 
     private ModBlocks() {
     }