Refine Cave terrain environment and spawning (#14)

README.md

@@ -198,7 +198,7 @@ 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
@@ -208,7 +208,7 @@ 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
+- `DISABLED` (default): never create Return Links automatically.
-  enters each Age.
+- `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_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/LEGACY_M7_AUDIT.md

@@ -46,7 +46,7 @@ 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
 

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/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.

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=0.6.5.2
+mod_version=0.6.7.0
 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);

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;
@@ -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);
@@ -117,6 +122,8 @@ public final class BookReceptacleBlock extends BaseEntityBlock {
                             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;
     }
 

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/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

@@ -118,4 +118,10 @@ 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(),
@@ -95,7 +96,13 @@ public final class AgeDimensionService {
 
     public static Optional<LinkTarget> resolve(ServerPlayer player, AgeReference reference,
                                                 OrderedWriting writing) {
+        return resolve(player, reference, writing, true);
+    }
+
+    public static Optional<LinkTarget> resolve(ServerPlayer player, AgeReference reference,
+                                                OrderedWriting writing, boolean generatePlatform) {
         AgeDefinition definition = AgeRegistrySavedData.resolveOrCreate(player.serverLevel(), reference, writing);
+        if (AgeRegistrySavedData.get(player.serverLevel()).isDead(definition.id())) return Optional.empty();
         ServerLevel level = ensureLoaded(player.getServer(), definition);
         if (level == null) {
             return Optional.empty();
@@ -104,7 +111,8 @@ 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 +130,7 @@ 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 +179,10 @@ 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 +211,7 @@ 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 +230,24 @@ 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 +258,11 @@ 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;
     }

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

@@ -10,13 +10,23 @@ public final class 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);
+        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. */

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(
@@ -88,7 +89,19 @@ 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 -> 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());
@@ -134,7 +176,9 @@ 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);
+        AgeTraits effectiveTraits = plan == null
+                ? AgeEnvironmentCompiler.forTerrain(traits, AgeRuntimeProfiles.resolve(seedProfile))
+                : AgeEnvironmentCompiler.apply(plan, traits);
         AgeInstability instability = AgeInstability.compute(plan, effectiveTraits, registries);
         AgeInstabilityPlan instabilityPlan = AgeInstabilityPlan.select(instability, seed);
         AgeDefinition created = new AgeDefinition(
@@ -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/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/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/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. */
+    /** Retained to read older test books; a newly edited book uses DISABLE_PLATFORM instead. */
     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 +39,16 @@ 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(DISABLE_PLATFORM)) lines.add(propertyName("disable_platform"));
     }
 
     private static Component propertyName(String name) {
@@ -54,6 +61,9 @@ 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 DISABLE_PLATFORM -> propertyName("disable_platform");
             default -> throw new IllegalArgumentException("Unknown link property flag: " + flag);
         };
     }

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

@@ -5,10 +5,13 @@ 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.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.item.ItemStack;
 import net.minecraft.tags.BlockTags;
 import net.minecraft.world.level.border.WorldBorder;
 import net.minecraft.world.level.levelgen.Heightmap;
@@ -32,6 +35,36 @@ public final class LinkingService {
         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);
@@ -53,7 +86,10 @@ 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;
         }
@@ -72,7 +108,10 @@ public final class LinkingService {
         ServerLevel destinationLevel = player.getServer().getLevel(target.location().dimension());
         if (destinationLevel == null) return LinkResult.MISSING_DIMENSION;
         boolean instant = destinationChunksLoaded(destinationLevel, target.location().pos());
-        Optional<Vec3> destination = resolveDestination(destinationLevel, target.location().pos(), true);
+        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);
@@ -88,11 +127,15 @@ public final class LinkingService {
         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;
 
         boolean instant = !portal || destinationChunksLoaded(destinationLevel, target.location().pos());
-        Optional<Vec3> destination = resolveDestination(destinationLevel, target.location().pos(), requiresFooting);
+        Optional<Vec3> destination = resolveDestination(destinationLevel,
+                landingOrigin(player, destinationLevel, target, properties), requiresFooting);
         if (destination.isEmpty()) {
             return LinkResult.NO_SAFE_DESTINATION;
         }
@@ -106,6 +149,17 @@ public final class LinkingService {
         return LinkResult.SUCCESS;
     }
 
+    /** Legacy relative links retain the traveller's offset from the source spawn. */
+    private static BlockPos landingOrigin(ServerPlayer player, ServerLevel destinationLevel,
+                                          LinkTarget target, LinkProperties properties) {
+        if (!properties.has(LinkProperties.RELATIVE_LINK)) return target.location().pos();
+        BlockPos sourceSpawn = player.serverLevel().getSharedSpawnPos();
+        BlockPos destinationSpawn = destinationLevel.getSharedSpawnPos();
+        BlockPos departure = player.blockPosition();
+        return destinationSpawn.offset(departure.getX() - sourceSpawn.getX(),
+                departure.getY() - sourceSpawn.getY(), departure.getZ() - sourceSpawn.getZ());
+    }
+
     /** Drop each inventory stack as an item entity at the departure point. */
     private static void dropInventoryAtSource(ServerPlayer player) {
         var inventory = player.getInventory();
@@ -230,6 +284,7 @@ public final class LinkingService {
         SUCCESS,
         MISSING_DIMENSION,
         INTRA_LINKING_REQUIRED,
+        INTRA_ONLY,
         NO_SAFE_DESTINATION
     }
 }

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;
@@ -25,6 +26,7 @@ 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)
@@ -34,6 +36,7 @@ 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.WRITING_DESK.get(), WritingDeskRenderer::new);
         event.registerBlockEntityRenderer(ModBlockEntities.STAR_FISSURE.get(), StarFissureRenderer::new);
@@ -45,6 +48,7 @@ public final class ClientEvents {
         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

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/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 +1,183 @@
+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.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++)
+            square(graphics, 5 + (index / 3) * 20, 10 + (index % 3) * 20,
+                    properties.has(FLAGS[index]), 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: "
+                            + (menu.book().getOrDefault(ModDataComponents.LINK_PROPERTIES.get(), LinkProperties.NONE)
+                            .has(LinkProperties.DISABLE_PLATFORM) ? "Off" : "On"))
+                            : 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);
+    }
+}

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;
@@ -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/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/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/Milestone7PolishGameTests.java

@@ -14,6 +14,26 @@ import net.neoforged.neoforge.gametest.PrefixGameTestTemplate;
 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(),

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

@@ -0,0 +1,23 @@
+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());
+    }
+
+    public static int capacity(ItemStack stack) {
+        return stack.is(ModItems.COLLATION_FOLDER.get()) ? MAX_PAGES
+                : stack.is(ModItems.NOTEBOOK.get()) ? NotebookContents.MAX_PAGES : 0;
+    }
+}

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

@@ -1,5 +1,6 @@
 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;
@@ -17,6 +18,7 @@ import net.minecraft.network.chat.Component;
 import net.minecraft.network.chat.MutableComponent;
 import net.minecraft.server.level.ServerPlayer;
 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;
@@ -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);
@@ -55,7 +61,10 @@ 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;
@@ -63,11 +72,10 @@ public final class DescriptiveBookItem extends Item {
 
         ServerLevel sourceLevel = player.serverLevel();
         Vec3 sourcePosition = player.position();
-        LinkProperties properties = stack.getOrDefault(ModDataComponents.LINK_PROPERTIES.get(), LinkProperties.NONE)
-                .forDescriptiveBook();
         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;
@@ -86,6 +94,7 @@ public final class DescriptiveBookItem extends Item {
             }
         }
         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

@@ -1,5 +1,6 @@
 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;
@@ -42,14 +43,19 @@ 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);
@@ -61,9 +67,11 @@ public final class LinkingBookItem extends Item {
         LinkProperties properties = stack.getOrDefault(ModDataComponents.LINK_PROPERTIES.get(), LinkProperties.NONE);
         LinkingService.LinkResult result = portal
                 ? LinkingService.travelPortal(player, target, properties)
-                : LinkingService.travel(player, target, properties);
+                : hand == null ? LinkingService.travel(player, target, properties)
+                : LinkingService.travelHandheld(player, hand, stack, target, properties, false);
         if (result == LinkingService.LinkResult.SUCCESS) {
             LinkVisualEffects.play(sourceLevel, sourcePosition, player, properties, portal);
+            ProgressionAdvancements.awardAgeTravel(player);
             player.displayClientMessage(Component.translatable("message.rivencraft.linking_book.linked"), true);
             return InteractionResultHolder.success(stack);
         }
@@ -71,6 +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 +39,9 @@ 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(), stack.is(net.dnorberg.rivencraft.registry.ModItems.COLLATION_FOLDER.get())
+                        ? CollationFolderItem.MAX_PAGES : NotebookContents.MAX_PAGES)
+                .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/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 +1,200 @@
+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 -> 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);
+            int capacity = CollationFolderItem.capacity(notebook);
-            for (int index = 0; index < NOTEBOOK_SLOTS; index++) {
+            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 sourceNotebook = CollationFolderItem.isCollection(sourceBook);
-        boolean targetNotebook = targetBook.is(ModItems.NOTEBOOK.get());
+        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/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("17");
         registrar.playToServer(RequestDescriptiveBookScreenPayload.TYPE, RequestDescriptiveBookScreenPayload.STREAM_CODEC,
                 ModNetworking::requestDescriptiveBookScreen);
         registrar.playToClient(OpenDescriptiveBookScreenPayload.TYPE, OpenDescriptiveBookScreenPayload.STREAM_CODEC,
@@ -85,6 +87,10 @@ public final class ModNetworking {
                 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 setBookBinderTitle(SetBookBinderTitlePayload payload, IPayloadContext context) {
@@ -95,6 +101,21 @@ 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 +184,9 @@ 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 +234,7 @@ 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 +268,8 @@ 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 +292,9 @@ 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 {

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/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",

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

@@ -27,9 +27,12 @@ public final class ModCreativeTabs {
                         output.accept(ModItems.DESCRIPTIVE_BOOK.get());
                         output.accept(ModItems.LINKING_BOOK.get());
                         output.accept(ModItems.NOTEBOOK.get());
+                        output.accept(ModItems.COLLATION_FOLDER.get());
+                        output.accept(ModItems.SEALED_NOTEBOOK.get());
                         output.accept(ModItems.INK_VIAL.get());
                         output.accept(ModItems.WRITING_DESK.get());
                         output.accept(ModItems.INK_MIXER.get());
+                        output.accept(ModItems.LINK_MODIFIER.get());
                         output.accept(ModItems.BOOK_BINDER.get());
                         output.accept(ModItems.CRYSTAL_BLOCK.get());
                         output.accept(ModItems.BOOK_RECEPTACLE.get());

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

@@ -0,0 +1,30 @@
+package net.dnorberg.rivencraft.registry;
+
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.entity.DroppedBookEntity;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.world.entity.EntityType;
+import net.minecraft.world.entity.MobCategory;
+import net.neoforged.bus.api.IEventBus;
+import net.neoforged.neoforge.registries.DeferredHolder;
+import net.neoforged.neoforge.registries.DeferredRegister;
+
+public final class ModEntities {
+    private static final DeferredRegister<EntityType<?>> ENTITIES =
+            DeferredRegister.create(Registries.ENTITY_TYPE, Rivencraft.MOD_ID);
+
+    public static final DeferredHolder<EntityType<?>, EntityType<DroppedBookEntity>> DROPPED_BOOK =
+            ENTITIES.register("dropped_book", () -> EntityType.Builder
+                    .<DroppedBookEntity>of(DroppedBookEntity::new, MobCategory.MISC)
+                    .sized(0.65F, 0.4F)
+                    .clientTrackingRange(10)
+                    .updateInterval(20)
+                    .build(Rivencraft.MOD_ID + ":dropped_book"));
+
+    private ModEntities() {
+    }
+
+    public static void register(IEventBus bus) {
+        ENTITIES.register(bus);
+    }
+}

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

@@ -5,6 +5,8 @@ import net.dnorberg.rivencraft.item.DescriptiveBookItem;
 import net.dnorberg.rivencraft.item.LinkingBookItem;
 import net.dnorberg.rivencraft.item.PageItem;
 import net.dnorberg.rivencraft.item.NotebookItem;
+import net.dnorberg.rivencraft.item.CollationFolderItem;
+import net.dnorberg.rivencraft.item.SealedNotebookItem;
 import net.dnorberg.rivencraft.item.InkVialItem;
 import net.minecraft.world.item.Item;
 import net.minecraft.world.item.BlockItem;
@@ -35,6 +37,10 @@ public final class ModItems {
             NotebookItem::new,
             new Item.Properties().stacksTo(1)
     );
+    public static final DeferredItem<CollationFolderItem> COLLATION_FOLDER = ITEMS.registerItem(
+            "collation_folder", CollationFolderItem::new, new Item.Properties().stacksTo(1));
+    public static final DeferredItem<SealedNotebookItem> SEALED_NOTEBOOK = ITEMS.registerItem(
+            "sealed_notebook", SealedNotebookItem::new, new Item.Properties().stacksTo(16));
     public static final DeferredItem<InkVialItem> INK_VIAL = ITEMS.registerItem(
             "ink_vial",
             InkVialItem::new,
@@ -43,6 +49,7 @@ public final class ModItems {
     public static final DeferredItem<BlockItem> WRITING_DESK = ITEMS.registerSimpleBlockItem(ModBlocks.WRITING_DESK);
     public static final DeferredItem<BlockItem> BOOK_BINDER = ITEMS.registerSimpleBlockItem(ModBlocks.BOOK_BINDER);
     public static final DeferredItem<BlockItem> INK_MIXER = ITEMS.registerSimpleBlockItem(ModBlocks.INK_MIXER);
+    public static final DeferredItem<BlockItem> LINK_MODIFIER = ITEMS.registerSimpleBlockItem(ModBlocks.LINK_MODIFIER);
     public static final DeferredItem<BlockItem> CRYSTAL_BLOCK = ITEMS.registerSimpleBlockItem(ModBlocks.CRYSTAL_BLOCK);
     public static final DeferredItem<BlockItem> BOOK_RECEPTACLE = ITEMS.registerSimpleBlockItem(ModBlocks.BOOK_RECEPTACLE);
     public static final DeferredItem<BlockItem> BUDDING_CRYSTAL = ITEMS.registerSimpleBlockItem(ModBlocks.BUDDING_CRYSTAL);

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

@@ -5,6 +5,7 @@ import net.dnorberg.rivencraft.menu.NotebookMenu;
 import net.dnorberg.rivencraft.menu.WritingDeskMenu;
 import net.dnorberg.rivencraft.menu.BookBinderMenu;
 import net.dnorberg.rivencraft.menu.InkMixerMenu;
+import net.dnorberg.rivencraft.menu.LinkModifierMenu;
 import net.minecraft.core.registries.Registries;
 import net.minecraft.world.inventory.MenuType;
 import net.neoforged.bus.api.IEventBus;
@@ -24,6 +25,8 @@ public final class ModMenus {
             MENUS.register("book_binder", () -> IMenuTypeExtension.create(BookBinderMenu::new));
     public static final DeferredHolder<MenuType<?>, MenuType<InkMixerMenu>> INK_MIXER =
             MENUS.register("ink_mixer", () -> IMenuTypeExtension.create(InkMixerMenu::new));
+    public static final DeferredHolder<MenuType<?>, MenuType<LinkModifierMenu>> LINK_MODIFIER =
+            MENUS.register("link_modifier", () -> IMenuTypeExtension.create(LinkModifierMenu::new));
 
     private ModMenus() {
     }

src/main/java/net/dnorberg/rivencraft/writing/WritingDeskCatalog.java

@@ -9,6 +9,7 @@ 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.item.CollationFolderItem;
 import net.minecraft.network.RegistryFriendlyByteBuf;
 import net.minecraft.resources.ResourceLocation;
 import net.minecraft.world.item.ItemStack;
@@ -24,7 +25,7 @@ public final class WritingDeskCatalog {
         for (int slot = 0; slot < WritingDeskBlockEntity.COLLECTIONS; slot++) {
             ItemStack collection = desk.getItem(slot);
             if (collection.is(ModItems.PAGE.get())) add(unique, collection);
-            if (collection.is(ModItems.NOTEBOOK.get())) {
+            if (CollationFolderItem.isCollection(collection)) {
                 List<ItemStack> pages = collection.getOrDefault(
                         ModDataComponents.NOTEBOOK_CONTENTS.get(), NotebookContents.EMPTY).pages();
                 pages.forEach(page -> add(unique, page));

src/main/resources/assets/rivencraft/blockstates/link_modifier.json

@@ -0,0 +1,8 @@
+{
+  "variants": {
+    "facing=north": { "model": "rivencraft:block/link_modifier" },
+    "facing=east": { "model": "rivencraft:block/link_modifier", "y": 90 },
+    "facing=south": { "model": "rivencraft:block/link_modifier", "y": 180 },
+    "facing=west": { "model": "rivencraft:block/link_modifier", "y": 270 }
+  }
+}

src/main/resources/assets/rivencraft/lang/en_us.json

@@ -15,8 +15,27 @@
   "item.rivencraft.link_property.disarm": "Disarm",
   "item.rivencraft.link_property.maintain_momentum": "Maintain Momentum",
   "item.rivencraft.link_property.intra_linking": "Intra Linking",
+  "item.rivencraft.link_property.intra_linking_only": "Intra-Linking Only",
+  "item.rivencraft.link_property.relative_link": "Relative Link",
+  "item.rivencraft.link_property.disable_platform": "Generate Platform: Off",
   "item.rivencraft.page.unresolved": "Unresolved Symbol Page",
   "item.rivencraft.notebook": "Notebook",
+  "item.rivencraft.collation_folder": "Collation Folder",
+  "item.rivencraft.sealed_notebook": "Sealed Notebook",
+  "block.rivencraft.link_modifier": "Link Modifier",
+  "container.rivencraft.link_modifier": "Link Modifier",
+  "screen.rivencraft.link_modifier.title": "Book title",
+  "screen.rivencraft.link_modifier.seed": "Age seed",
+  "screen.rivencraft.link_modifier.seed_warning": "Changing the seed preserves existing chunks but changes newly generated terrain. Press Enter to apply. The Age must be empty.",
+  "message.rivencraft.link_modifier.seed_changed": "Age seed changed. Existing chunks remain; newly generated chunks use the new seed.",
+  "message.rivencraft.link_modifier.seed_failed": "Could not change seed. Use a signed whole number and ensure no players are in the Age.",
+  "screen.rivencraft.link_modifier.retire": "Retire Age",
+  "screen.rivencraft.link_modifier.confirm": "Confirm!",
+  "message.rivencraft.link_modifier.delete.retired": "Age retired. Its terrain was archived outside the active world.",
+  "message.rivencraft.link_modifier.delete.already_dead": "This Age is already retired.",
+  "message.rivencraft.link_modifier.delete.occupied": "Cannot retire an Age while players are inside it.",
+  "message.rivencraft.link_modifier.delete.unload_failed": "Could not unload this Age; its data is unchanged.",
+  "message.rivencraft.link_modifier.delete.storage_failed": "Could not archive this Age's data; it was not retired.",
   "item.rivencraft.notebook.pages": "Pages: %s/%s",
   "item.rivencraft.notebook.unresolved": "Unresolved pages: %s",
   "item.rivencraft.ink_vial": "Ink Vial",
@@ -88,6 +107,7 @@
   "message.rivencraft.linking_book.missing_dimension": "That dimension is unavailable",
   "message.rivencraft.linking_book.unsafe": "No safe destination was found near the link",
   "message.rivencraft.linking_book.intra_required": "This book needs an Intra Linking panel for same-dimension travel",
+  "message.rivencraft.linking_book.intra_only": "This book can only link within its current dimension",
   "message.rivencraft.descriptive_book.unwritten": "This Descriptive Book is unwritten",
   "message.rivencraft.descriptive_book.created": "Created Age: %s",
   "message.rivencraft.descriptive_book.unavailable": "That Age is unavailable",
@@ -369,5 +389,21 @@
   "symbol.rivencraft.corrupted.medium": "Corrupted Page",
   "symbol.rivencraft.corrupted.medium.description": "The writing shifts beyond comprehension.",
   "symbol.rivencraft.corrupted.small": "Corrupted Page",
-  "symbol.rivencraft.corrupted.small.description": "The writing shifts beyond comprehension."
+  "symbol.rivencraft.corrupted.small.description": "The writing shifts beyond comprehension.",
+  "advancement.rivencraft.root.title": "The Ending Has Not Yet Been Written",
+  "advancement.rivencraft.root.description": "Begin the Art of writing and linking Ages.",
+  "advancement.rivencraft.page.title": "A Strange Page",
+  "advancement.rivencraft.page.description": "Find a Page marked with the language of Ages.",
+  "advancement.rivencraft.linking_book.title": "A Way Back",
+  "advancement.rivencraft.linking_book.description": "Obtain a Linking Book and remember where you came from.",
+  "advancement.rivencraft.link_panel.title": "D'ni Ink",
+  "advancement.rivencraft.link_panel.description": "Create a Link Panel at the Ink Mixer.",
+  "advancement.rivencraft.copy_page.title": "The Art of Writing",
+  "advancement.rivencraft.copy_page.description": "Copy a Page at the Writing Desk.",
+  "advancement.rivencraft.bind_age.title": "A Book of Ages",
+  "advancement.rivencraft.bind_age.description": "Bind a completed Descriptive Book.",
+  "advancement.rivencraft.enter_age.title": "The Journey Begins",
+  "advancement.rivencraft.enter_age.description": "Safely link into an Age you have written.",
+  "advancement.rivencraft.open_portal.title": "A Window Between Ages",
+  "advancement.rivencraft.open_portal.description": "Activate a Crystal Portal with a bound book."
 }

src/main/resources/assets/rivencraft/models/block/link_modifier.json

@@ -0,0 +1,120 @@
+{
+    "parent": "block/block",
+    "textures": {
+        "particle": "rivencraft:block/link_modifier_base",
+        "0": "rivencraft:block/link_modifier_base",
+        "1": "rivencraft:block/link_modifier_details"
+    },
+    "elements": [
+        {
+            "from": [ 0.0, 0.0, 0.0 ],
+            "to": [ 16.0, 12.0, 16.0 ],
+            "faces": {
+                "north": { "texture": "#0", "uv": [ 0.0, 4.0, 4.0, 7.0 ] },
+                "east": { "texture": "#0", "uv": [ 4.0, 4.0, 8.0, 7.0 ] },
+                "south": { "texture": "#0", "uv": [ 8.0, 4.0, 12.0, 7.0 ] },
+                "west": { "texture": "#0", "uv": [ 12.0, 4.0, 16.0, 7.0 ] },
+                "up": { "texture": "#0", "uv": [ 4.0, 0.0, 8.0, 4.0 ] },
+                "down": { "texture": "#0", "uv": [ 8.0, 0.0, 12.0, 4.0 ] }
+            }
+        },
+        {
+            "from": [ 1.5, 12.0, 11.0 ],
+            "to": [ 3.5, 13.0, 13.0 ],
+            "faces": {
+                "north": { "texture": "#1", "uv": [ 0.0, 15.0, 1.0, 15.5 ] },
+                "east": { "texture": "#1", "uv": [ 0.0, 14.0, 1.0, 14.5 ] },
+                "south": { "texture": "#1", "uv": [ 0.0, 13.0, 1.0, 13.5 ] },
+                "west": { "texture": "#1", "uv": [ 1.0, 13.0, 1.0, 13.5 ] },
+                "up": { "texture": "#1", "uv": [ 2.0, 14.0, 3.0, 15.0 ] },
+                "down": { "texture": "#1", "uv": [ 1.0, 13.0, 2.0, 14.0 ] }
+            }
+        },
+        {
+            "from": [ 3.7, 12.0, 11.0 ],
+            "to": [ 5.7, 13.0, 13.0 ],
+            "faces": {
+                "north": { "texture": "#1", "uv": [ 0.0, 15.0, 1.0, 15.5 ] },
+                "east": { "texture": "#1", "uv": [ 0.0, 14.0, 1.0, 14.5 ] },
+                "south": { "texture": "#1", "uv": [ 0.0, 13.0, 1.0, 13.5 ] },
+                "west": { "texture": "#1", "uv": [ 1.0, 13.0, 1.0, 13.5 ] },
+                "up": { "texture": "#1", "uv": [ 2.0, 14.0, 3.0, 15.0 ] },
+                "down": { "texture": "#1", "uv": [ 1.0, 13.0, 2.0, 14.0 ] }
+            }
+        },
+        {
+            "from": [ 5.9, 12.0, 11.0 ],
+            "to": [ 7.9, 13.0, 13.0 ],
+            "faces": {
+                "north": { "texture": "#1", "uv": [ 0.0, 15.0, 1.0, 15.5 ] },
+                "east": { "texture": "#1", "uv": [ 0.0, 14.0, 1.0, 14.5 ] },
+                "south": { "texture": "#1", "uv": [ 0.0, 13.0, 1.0, 13.5 ] },
+                "west": { "texture": "#1", "uv": [ 1.0, 13.0, 1.0, 13.5 ] },
+                "up": { "texture": "#1", "uv": [ 2.0, 14.0, 3.0, 15.0 ] },
+                "down": { "texture": "#1", "uv": [ 1.0, 13.0, 2.0, 14.0 ] }
+            }
+        },
+        {
+            "from": [ 8.1, 12.0, 11.0 ],
+            "to": [ 10.1, 13.0, 13.0 ],
+            "faces": {
+                "north": { "texture": "#1", "uv": [ 0.0, 15.0, 1.0, 15.5 ] },
+                "east": { "texture": "#1", "uv": [ 0.0, 14.0, 1.0, 14.5 ] },
+                "south": { "texture": "#1", "uv": [ 0.0, 13.0, 1.0, 13.5 ] },
+                "west": { "texture": "#1", "uv": [ 1.0, 13.0, 1.0, 13.5 ] },
+                "up": { "texture": "#1", "uv": [ 2.0, 14.0, 3.0, 15.0 ] },
+                "down": { "texture": "#1", "uv": [ 1.0, 13.0, 2.0, 14.0 ] }
+            }
+        },
+        {
+            "from": [ 10.3, 12.0, 11.0 ],
+            "to": [ 12.3, 13.0, 13.0 ],
+            "faces": {
+                "north": { "texture": "#1", "uv": [ 0.0, 15.0, 1.0, 15.5 ] },
+                "east": { "texture": "#1", "uv": [ 0.0, 14.0, 1.0, 14.5 ] },
+                "south": { "texture": "#1", "uv": [ 0.0, 13.0, 1.0, 13.5 ] },
+                "west": { "texture": "#1", "uv": [ 1.0, 13.0, 1.0, 13.5 ] },
+                "up": { "texture": "#1", "uv": [ 2.0, 14.0, 3.0, 15.0 ] },
+                "down": { "texture": "#1", "uv": [ 1.0, 13.0, 2.0, 14.0 ] }
+            }
+        },
+        {
+            "from": [ 12.5, 12.0, 11.0 ],
+            "to": [ 14.5, 13.0, 13.0 ],
+            "faces": {
+                "north": { "texture": "#1", "uv": [ 0.0, 15.0, 1.0, 15.5 ] },
+                "east": { "texture": "#1", "uv": [ 0.0, 14.0, 1.0, 14.5 ] },
+                "south": { "texture": "#1", "uv": [ 0.0, 13.0, 1.0, 13.5 ] },
+                "west": { "texture": "#1", "uv": [ 1.0, 13.0, 1.0, 13.5 ] },
+                "up": { "texture": "#1", "uv": [ 2.0, 14.0, 3.0, 15.0 ] },
+                "down": { "texture": "#1", "uv": [ 1.0, 13.0, 2.0, 14.0 ] }
+            }
+        },
+        {
+            "from": [ 2.0, 9.4, 1.0 ],
+            "to": [ 14.0, 12.4, 8.0 ],
+            "rotation": { "origin": [ 8.0, 8.0, 8.0 ], "axis": "x", "angle": 22.5 },
+            "faces": {
+                "north": { "texture": "#1", "uv": [ 0.0, 4.0, 6.0, 5.5 ] },
+                "east": { "texture": "#1", "uv": [ 6.0, 4.0, 9.5, 5.5 ] },
+                "south": { "texture": "#1", "uv": [ 0.0, 6.0, 6.0, 7.5 ] },
+                "west": { "texture": "#1", "uv": [ 6.0, 6.0, 9.5, 7.5 ] },
+                "up": { "texture": "#1", "uv": [ 0.0, 0.0, 6.0, 3.5 ] },
+                "down": { "texture": "#1", "uv": [ 6.0, 0.0, 12.0, 3.5 ] }
+            }
+        },
+        {
+            "from": [ 4.0, 11.5, 3.5 ],
+            "to": [ 12.0, 15.5, 5.5 ],
+            "rotation": { "origin": [ 8.0, 8.0, 8.0 ], "axis": "x", "angle": 22.5 },
+            "faces": {
+                "north": { "texture": "#1", "uv": [ 1.0, 9.0, 5.0, 11.0 ] },
+                "east": { "texture": "#1", "uv": [ 0.0, 8.0, 1.0, 11.0 ] },
+                "south": { "texture": "#1", "uv": [ 6.0, 9.0, 10.0, 11.0 ] },
+                "west": { "texture": "#1", "uv": [ 5.0, 9.0, 6.0, 11.0 ] },
+                "up": { "texture": "#1", "uv": [ 1.0, 8.0, 5.0, 9.0 ] },
+                "down": { "texture": "#1", "uv": [ 5.0, 8.0, 9.0, 9.0 ] }
+            }
+        }
+    ]
+}

src/main/resources/assets/rivencraft/models/item/collation_folder.json

@@ -0,0 +1,4 @@
+{
+  "parent": "minecraft:item/generated",
+  "textures": { "layer0": "rivencraft:item/collation_folder" }
+}

src/main/resources/assets/rivencraft/models/item/link_modifier.json

@@ -0,0 +1 @@
+{ "parent": "rivencraft:block/link_modifier" }

src/main/resources/assets/rivencraft/models/item/sealed_notebook.json

@@ -0,0 +1,4 @@
+{
+  "parent": "minecraft:item/generated",
+  "textures": { "layer0": "rivencraft:item/sealed_notebook" }
+}

src/main/resources/data/rivencraft/advancement/progression/bind_age.json

@@ -0,0 +1,19 @@
+{
+  "parent": "rivencraft:progression/link_panel",
+  "display": {
+    "icon": {
+      "id": "rivencraft:descriptive_book"
+    },
+    "title": {
+      "translate": "advancement.rivencraft.bind_age.title"
+    },
+    "description": {
+      "translate": "advancement.rivencraft.bind_age.description"
+    }
+  },
+  "criteria": {
+    "completed": {
+      "trigger": "minecraft:impossible"
+    }
+  }
+}

src/main/resources/data/rivencraft/advancement/progression/copy_page.json

@@ -0,0 +1,19 @@
+{
+  "parent": "rivencraft:progression/page",
+  "display": {
+    "icon": {
+      "id": "rivencraft:writing_desk"
+    },
+    "title": {
+      "translate": "advancement.rivencraft.copy_page.title"
+    },
+    "description": {
+      "translate": "advancement.rivencraft.copy_page.description"
+    }
+  },
+  "criteria": {
+    "completed": {
+      "trigger": "minecraft:impossible"
+    }
+  }
+}

src/main/resources/data/rivencraft/advancement/progression/enter_age.json

@@ -0,0 +1,20 @@
+{
+  "parent": "rivencraft:progression/bind_age",
+  "display": {
+    "icon": {
+      "id": "rivencraft:descriptive_book"
+    },
+    "title": {
+      "translate": "advancement.rivencraft.enter_age.title"
+    },
+    "description": {
+      "translate": "advancement.rivencraft.enter_age.description"
+    },
+    "frame": "goal"
+  },
+  "criteria": {
+    "completed": {
+      "trigger": "minecraft:impossible"
+    }
+  }
+}

src/main/resources/data/rivencraft/advancement/progression/link_panel.json

@@ -0,0 +1,19 @@
+{
+  "parent": "rivencraft:progression/root",
+  "display": {
+    "icon": {
+      "id": "rivencraft:ink_mixer"
+    },
+    "title": {
+      "translate": "advancement.rivencraft.link_panel.title"
+    },
+    "description": {
+      "translate": "advancement.rivencraft.link_panel.description"
+    }
+  },
+  "criteria": {
+    "completed": {
+      "trigger": "minecraft:impossible"
+    }
+  }
+}

src/main/resources/data/rivencraft/advancement/progression/linking_book.json

@@ -0,0 +1,26 @@
+{
+  "parent": "rivencraft:progression/root",
+  "display": {
+    "icon": {
+      "id": "rivencraft:linking_book"
+    },
+    "title": {
+      "translate": "advancement.rivencraft.linking_book.title"
+    },
+    "description": {
+      "translate": "advancement.rivencraft.linking_book.description"
+    }
+  },
+  "criteria": {
+    "completed": {
+      "trigger": "minecraft:inventory_changed",
+      "conditions": {
+        "items": [
+          {
+            "items": "rivencraft:linking_book"
+          }
+        ]
+      }
+    }
+  }
+}

src/main/resources/data/rivencraft/advancement/progression/open_portal.json

@@ -0,0 +1,20 @@
+{
+  "parent": "rivencraft:progression/linking_book",
+  "display": {
+    "icon": {
+      "id": "rivencraft:book_receptacle"
+    },
+    "title": {
+      "translate": "advancement.rivencraft.open_portal.title"
+    },
+    "description": {
+      "translate": "advancement.rivencraft.open_portal.description"
+    },
+    "frame": "goal"
+  },
+  "criteria": {
+    "completed": {
+      "trigger": "minecraft:impossible"
+    }
+  }
+}

src/main/resources/data/rivencraft/advancement/progression/page.json

@@ -0,0 +1,26 @@
+{
+  "parent": "rivencraft:progression/root",
+  "display": {
+    "icon": {
+      "id": "rivencraft:page"
+    },
+    "title": {
+      "translate": "advancement.rivencraft.page.title"
+    },
+    "description": {
+      "translate": "advancement.rivencraft.page.description"
+    }
+  },
+  "criteria": {
+    "completed": {
+      "trigger": "minecraft:inventory_changed",
+      "conditions": {
+        "items": [
+          {
+            "items": "rivencraft:page"
+          }
+        ]
+      }
+    }
+  }
+}

src/main/resources/data/rivencraft/advancement/progression/root.json

@@ -0,0 +1,21 @@
+{
+  "display": {
+    "icon": {
+      "id": "rivencraft:descriptive_book"
+    },
+    "title": {
+      "translate": "advancement.rivencraft.root.title"
+    },
+    "description": {
+      "translate": "advancement.rivencraft.root.description"
+    },
+    "background": "minecraft:textures/gui/advancements/backgrounds/stone.png",
+    "show_toast": false,
+    "announce_to_chat": false
+  },
+  "criteria": {
+    "completed": {
+      "trigger": "minecraft:tick"
+    }
+  }
+}

src/main/resources/data/rivencraft/advancement/recipes/misc/book_binder.json

@@ -0,0 +1,32 @@
+{
+  "parent": "minecraft:recipes/root",
+  "criteria": {
+    "has_material": {
+      "trigger": "minecraft:inventory_changed",
+      "conditions": {
+        "items": [
+          {
+            "items": "minecraft:iron_ingot"
+          }
+        ]
+      }
+    },
+    "has_the_recipe": {
+      "trigger": "minecraft:recipe_unlocked",
+      "conditions": {
+        "recipe": "rivencraft:book_binder"
+      }
+    }
+  },
+  "requirements": [
+    [
+      "has_material",
+      "has_the_recipe"
+    ]
+  ],
+  "rewards": {
+    "recipes": [
+      "rivencraft:book_binder"
+    ]
+  }
+}

src/main/resources/data/rivencraft/advancement/recipes/misc/ink_mixer.json

@@ -0,0 +1,32 @@
+{
+  "parent": "minecraft:recipes/root",
+  "criteria": {
+    "has_material": {
+      "trigger": "minecraft:inventory_changed",
+      "conditions": {
+        "items": [
+          {
+            "items": "minecraft:glass_bottle"
+          }
+        ]
+      }
+    },
+    "has_the_recipe": {
+      "trigger": "minecraft:recipe_unlocked",
+      "conditions": {
+        "recipe": "rivencraft:ink_mixer"
+      }
+    }
+  },
+  "requirements": [
+    [
+      "has_material",
+      "has_the_recipe"
+    ]
+  ],
+  "rewards": {
+    "recipes": [
+      "rivencraft:ink_mixer"
+    ]
+  }
+}

src/main/resources/data/rivencraft/advancement/recipes/misc/notebook.json

@@ -0,0 +1,32 @@
+{
+  "parent": "minecraft:recipes/root",
+  "criteria": {
+    "has_material": {
+      "trigger": "minecraft:inventory_changed",
+      "conditions": {
+        "items": [
+          {
+            "items": "minecraft:leather"
+          }
+        ]
+      }
+    },
+    "has_the_recipe": {
+      "trigger": "minecraft:recipe_unlocked",
+      "conditions": {
+        "recipe": "rivencraft:notebook"
+      }
+    }
+  },
+  "requirements": [
+    [
+      "has_material",
+      "has_the_recipe"
+    ]
+  ],
+  "rewards": {
+    "recipes": [
+      "rivencraft:notebook"
+    ]
+  }
+}

src/main/resources/data/rivencraft/advancement/recipes/misc/writing_desk.json

@@ -0,0 +1,32 @@
+{
+  "parent": "minecraft:recipes/root",
+  "criteria": {
+    "has_material": {
+      "trigger": "minecraft:inventory_changed",
+      "conditions": {
+        "items": [
+          {
+            "items": "minecraft:feather"
+          }
+        ]
+      }
+    },
+    "has_the_recipe": {
+      "trigger": "minecraft:recipe_unlocked",
+      "conditions": {
+        "recipe": "rivencraft:writing_desk"
+      }
+    }
+  },
+  "requirements": [
+    [
+      "has_material",
+      "has_the_recipe"
+    ]
+  ],
+  "rewards": {
+    "recipes": [
+      "rivencraft:writing_desk"
+    ]
+  }
+}

src/main/resources/data/rivencraft/loot_table/blocks/link_modifier.json

@@ -0,0 +1,4 @@
+{
+  "type": "minecraft:block",
+  "pools": [{ "rolls": 1, "entries": [{ "type": "minecraft:item", "name": "rivencraft:link_modifier" }] }]
+}

src/main/resources/data/rivencraft/loot_table/chests/mystcraft_library.json

@@ -9,7 +9,7 @@
         { "type": "minecraft:item", "name": "minecraft:leather", "weight": 5,
           "functions": [{ "function": "minecraft:set_count", "count": { "type": "minecraft:uniform", "min": 1, "max": 3 } }] },
         { "type": "minecraft:item", "name": "rivencraft:ink_vial", "weight": 4 },
-        { "type": "minecraft:item", "name": "minecraft:book", "weight": 3 },
+        { "type": "minecraft:item", "name": "rivencraft:sealed_notebook", "weight": 20 },
         { "type": "minecraft:item", "name": "minecraft:experience_bottle", "weight": 1 }
       ]
     },
@@ -17,7 +17,7 @@
       "rolls": { "type": "minecraft:uniform", "min": 1, "max": 2 },
       "entries": [
         { "type": "minecraft:item", "name": "rivencraft:ink_vial", "weight": 3 },
-        { "type": "minecraft:item", "name": "minecraft:book", "weight": 2 },
+        { "type": "minecraft:item", "name": "rivencraft:sealed_notebook", "weight": 2 },
         { "type": "minecraft:item", "name": "minecraft:experience_bottle", "weight": 1 }
       ]
     }

src/main/resources/rivencraft.mixins.json

@@ -4,6 +4,7 @@
   "package": "net.dnorberg.rivencraft.mixin",
   "compatibilityLevel": "JAVA_21",
   "mixins": [
+    "AgeDimensionSeedMixin",
     "AgeDungeonPlacementMixin",
     "AgeStructureBiomeMixin",
     "StructurePlacementAccessor"