Add mod-aware Dense Ores age feature (#55)

docs/AGE_PROFILES.md

@@ -65,6 +65,50 @@ writing. Each unpaired material gets its own compatible feature, and repeated
 decorations use separate placement rolls. Repeated unmodified feature pages
 choose different compatible materials until their material pool is exhausted.
 
+Structure pages are separate Feature symbols. Legacy's Dungeons, Mineshafts,
+Nether Fortresses, Strongholds, and Villages have writable pages, as do modern
+Trial Chambers, Bastion Remnants, Buried Treasure, Shipwrecks, Ocean Ruins,
+Pillager Outposts, Ruined Portals, Nether Fossils, Ancient Cities, and Trail
+Ruins. They use Minecraft's 1.21.1 structure templates and placement rules,
+not a recreation of 1.12.2 structure geometry. A page enables only its own
+structure set; absent pages do not inherit these structures from a biome.
+Nether Fortresses and Bastions use separate sets instead of vanilla's shared
+Nether-complexes set, so writing one does not enable the other. Dungeons use
+the vanilla monster-room feature with eight attempts per chunk; unpaged Ages
+do not inherit biome-default monster-room attempts. A page-free random Age
+may choose zero to two distinct compatible structure types, frozen on creation.
+An authored structure needs a compatible biome in the Age's selected pool.
+Fortresses, Bastions, and Nether Fossils require Cave terrain plus a Nether
+biome; surface-only structures reject Cave terrain. Void rejects all of these
+structure pages. Villages and Strongholds can also be written into Flat Ages.
+
+For visual testing, write a Standard/Plains/Single Age with Mineshafts,
+Villages, and Trial Chambers, then use `/locate structure` in that Age to find
+each. An unwritten Pillager Outpost should not locate there. Test a Cave Age
+with Nether Wastes/Single and either the Nether Fortresses or Bastion page:
+only the selected type should locate. Ocean structures need their matching
+ocean or beach biome page; Ancient Cities need Deep Dark. Check the new pages
+in Rivencraft's Feature creative tab and JEI as well.
+
+**Dense Ores** is an authored-only Feature page. Each copy replays one extra
+pass of every ore placement registered in the Age's nearby biomes, using that
+placement's existing height, vein-size, rarity, and biome rules. It therefore
+also densifies conventional mod-added ores without hard-coded mod IDs. Output
+blocks tagged `c:ores` qualify; OreConfiguration outputs with `_ore` in their
+registry name also qualify. A mod with a custom, non-OreConfiguration placed
+feature can opt in by tagging that feature `rivencraft:dense_ores`. Non-ore
+stone/dirt blobs are not repeated. Flat and Void reject the page, as does a
+biome pool without any ore placements. Page-free random Ages never roll Dense
+Ores. The extra pass applies only as new chunks generate; it does not retrofit
+existing chunks or discover ore systems that bypass biome placed features.
+
+For an in-game check, write a Standard/Plains/Single Age with Dense Ores and
+verify that new underground chunks contain visibly more vanilla ore while
+stone/dirt blob frequency remains unchanged. With an ore-adding mod installed,
+write an Age using a biome where that mod registers its ore and verify the ore
+also appears more often. Check that Flat plus Dense Ores is rejected by the
+Binder and that a random, Link-Panel-only Age has no Dense Ores feature page.
+
 For an in-game visual check, bind Descriptive Books with a Link Panel,
 one of Standard, Amplified, Sky Islands, Flat, or Void terrain, and the Floating Islands
 feature page in that order. Fly through each Age at roughly Y=170–220 and

docs/LEGACY_AGE_GRAMMAR_AUDIT.md

@@ -18,7 +18,7 @@ Legacy does **not** reject a book just because it omits terrain, biome, weather,
 | `WeatherNorm`, `Fast`, `Slow`, `Off`, `On`, `Cloudy`, `Rain`, `Snow`, `Storm` | `AgeTraits.Weather` has matching names except Legacy `On` maps to `ALWAYS` | Compile weather semantics separately from biome selection. `Snow` must remain deferred until optional season integration; do not silently substitute another weather mode. |
 | Suns, moons, starfields; angle, phase, period, color/gradient/sunset modifiers | One `celestialPeriod`, `celestialAngle`, `celestialPhase` on `AgeTraits` | Compile only the representable single-cycle subset first. Multiple celestial bodies, independent periods, custom stars, gradients and sunsets need a richer definition and renderer, not flattening into one value. |
 | Sky/fog/cloud/grass/foliage/water colors, natural variants, horizon, rainbow | Existing sky/dimension visuals and preview | Require an explicit modern client/biome-color design; metadata-only symbol pages must not pretend to change rendering. |
-| Caves, ores, huge trees, lakes, floating islands, tendrils, skylands, spheres, spikes, crystals; vanilla villages, strongholds, mineshafts, dungeons, fortresses, obelisks, fissures | Current cave profile, vanilla data-pack generation, and authored Floating Islands/Tendrils/Skylands/Spheres/Spikes | Compile supported vanilla placements and port bespoke shapes explicitly. Remaining bespoke structures and polish stay in later issues. |
+| Caves, ores, huge trees, lakes, floating islands, tendrils, skylands, spheres, spikes, crystals; vanilla villages, strongholds, mineshafts, dungeons, fortresses, obelisks, fissures | Current cave profile, authored Floating Islands/Tendrils/Skylands/Spheres/Spikes, and page-gated vanilla Dungeons/Mineshafts/Nether Fortresses/Strongholds/Villages | The five Legacy vanilla structure symbols now gate Minecraft 1.21.1 generation. Dungeons use monster-room placement; the others use vanilla structure sets. Bespoke obelisks, fissures, crystals, and exact 1.12 structure geometry remain separate work. |
 | `EnvAccel`, explosions, lightning, meteors, scorching; PvP and dummy suppression pages | No equivalent Age-definition effect | Defer environmental hazards/instability effects to milestone 6, PvP rule to a separately scoped server policy; retain authored IDs without fake behavior. |
 
 The Legacy symbol list and page names come from [ModSymbols](https://github.com/Mystcraft/Mystcraft-Legacy/blob/9bc8ddc061845df0cd5ea47f4fdef773cff786ae/src/main/java/com/xcompwiz/mystcraft/data/ModSymbols.java#L129-L240) and [SymbolRules](https://github.com/Mystcraft/Mystcraft-Legacy/blob/9bc8ddc061845df0cd5ea47f4fdef773cff786ae/src/main/java/com/xcompwiz/mystcraft/data/SymbolRules.java#L19-L137). Rivencraft's [catalog](../src/main/java/net/dnorberg/rivencraft/writing/SymbolCatalog.java) currently holds display metadata only; its built-in set is just standard terrain, native biomes, normal weather, normal lighting, normal time, and caves. [OrderedWriting](../src/main/java/net/dnorberg/rivencraft/writing/OrderedWriting.java) preserves page order, but no compiler yet connects it to [AgeTraits](../src/main/java/net/dnorberg/rivencraft/book/AgeTraits.java) or [Age profiles](AGE_PROFILES.md).

gradle.properties

@@ -36,7 +36,7 @@ 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=0.4.14.0
+mod_version=0.4.16.0
 immersive_portals_version=6.0.7
 terrablender_version=4.1.0.8
 serene_seasons_version_id=B6nTjh4b

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

@@ -329,7 +329,8 @@ public final class AgeDimensionService {
                 Registries.NOISE_SETTINGS, profile.noiseSettings());
         NoiseGeneratorSettings baseSettings = noiseSettings.getOrThrow(settingsKey).value();
         Holder<NoiseGeneratorSettings> settings = Holder.direct(withBiomeMaterialRules(baseSettings));
-        return features.isEmpty() ? new NoiseBasedChunkGenerator(biomeSource, settings)
+        return age.generationVersion() < AgeDefinition.CURRENT_GENERATION_VERSION
+                ? new NoiseBasedChunkGenerator(biomeSource, settings)
                 : new AgeFeatureChunkGenerator(biomeSource, settings, features, age.seed());
     }
 

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

@@ -10,8 +10,10 @@ import java.util.Map;
 import java.util.Optional;
 import java.util.Random;
 import net.dnorberg.rivencraft.writing.BlockSymbolPages;
+import net.dnorberg.rivencraft.writing.OrderedWriting;
 import net.dnorberg.rivencraft.writing.SymbolSemantics;
 import net.dnorberg.rivencraft.writing.WritingGrammar;
+import net.dnorberg.rivencraft.world.AgeDenseOres;
 import net.minecraft.core.Holder;
 import net.minecraft.core.RegistryAccess;
 import net.minecraft.core.registries.BuiltInRegistries;
@@ -49,6 +51,10 @@ public final class AgeFeatureSelection {
                 .map(symbol -> symbol.semantics()).toList(), profile, ageSeed);
         for (Choice choice : choices) {
             String error = error(choice.id(), profile, registries);
+            if (error == null && AgeStructureSelection.feature(choice.id()))
+                error = AgeStructureSelection.error(choice.id(), profile, biomes, registries);
+            if (error == null && choice.id().equals(AgeDenseOres.ID))
+                error = AgeDenseOres.error(profile, biomes, registries);
             if (error == null) error = materialError(choice);
             if (error != null) throw new IllegalArgumentException(error);
             if (surfaceVegetation(choice.id()) && biomes.biomes().stream()
@@ -163,6 +169,9 @@ public final class AgeFeatureSelection {
         if (profile.terrain() == AgeRuntimeProfile.Terrain.NOISE
                 && Math.floorMod(mix(ageSeed ^ RANDOM_SKYLANDS_SALT), 8) == 0)
             choices.add(new Choice(id("skylands"), Optional.empty()));
+        AgeBiomeSelection biomes = AgeBiomeSelection.compile(WritingGrammar.parse(OrderedWriting.EMPTY),
+                AgeTraits.select(ageSeed), profile, ageSeed, registries);
+        choices.addAll(AgeStructureSelection.randomChoices(ageSeed, profile, biomes, registries));
         return List.copyOf(choices);
     }
 
@@ -187,6 +196,10 @@ public final class AgeFeatureSelection {
     }
 
     public static String error(ResourceLocation choice, AgeRuntimeProfile profile, RegistryAccess registries) {
+        if (AgeStructureSelection.feature(choice))
+            return AgeStructureSelection.error(choice, profile, null, registries);
+        if (choice.equals(AgeDenseOres.ID))
+            return AgeDenseOres.error(profile, null, registries);
         if (skylands(choice)) return null;
         if (tendrils(choice)) return null;
         if (spheres(choice)) return null;
@@ -313,6 +326,7 @@ public final class AgeFeatureSelection {
             case "trees" -> ResourceLocation.withDefaultNamespace("trees_plains");
             case "huge_trees" -> ResourceLocation.withDefaultNamespace("trees_old_growth_spruce_taiga");
             case "rocks" -> ResourceLocation.withDefaultNamespace("forest_rock");
+            case "dungeons" -> ResourceLocation.fromNamespaceAndPath("rivencraft", "dungeons");
             case "surface_lakes", "lava_lakes" -> ResourceLocation.withDefaultNamespace("lake_lava_surface");
             case "deep_lakes" -> ResourceLocation.withDefaultNamespace("lake_lava_underground");
             default -> null;

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

@@ -74,12 +74,16 @@ public final class AgePersistenceGameTests {
             helper.assertTrue(age.randomFeatures().stream().filter(choice ->
                     AgeFeatureSelection.skylands(choice.id())).count() <= 1,
                     "A random Age may roll at most one Skylands filter");
+            helper.assertTrue(age.randomFeatures().stream().filter(choice ->
+                    AgeStructureSelection.feature(choice.id())).count() <= 2,
+                    "A random Age may roll at most two distinct structure features");
             for (AgeFeatureSelection.Choice choice : age.randomFeatures()) {
                 helper.assertTrue(AgeFeatureSelection.skylands(choice.id())
+                                || AgeStructureSelection.feature(choice.id())
                                 ? choice.material().isEmpty()
                                 : choice.material().isPresent()
                                 && AgeFeatureSelection.materialError(choice) == null,
-                        "Random material features, including Spheres and Spikes, need valid blocks or fluids; Skylands needs none");
+                        "Random material features need valid blocks or fluids; Skylands and structures need none");
             }
         }
         AgeRegistrySavedData registry = AgeRegistrySavedData.get(helper.getLevel());

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

@@ -0,0 +1,100 @@
+package net.dnorberg.rivencraft.book;
+
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+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.core.registries.Registries;
+import net.minecraft.gametest.framework.GameTest;
+import net.minecraft.gametest.framework.GameTestHelper;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.resources.ResourceLocation;
+import net.minecraft.world.level.levelgen.structure.BuiltinStructureSets;
+import net.minecraft.world.level.levelgen.structure.StructureSet;
+import net.neoforged.neoforge.gametest.GameTestHolder;
+import net.neoforged.neoforge.gametest.PrefixGameTestTemplate;
+
+/** Authored structure pages gate their own structure sets without enabling unrelated structures. */
+@GameTestHolder(Rivencraft.MOD_ID)
+@PrefixGameTestTemplate(false)
+public final class AgeStructureGameTests {
+    private static final Map<String, ResourceLocation> SETS = Map.ofEntries(
+            Map.entry("mineshafts", BuiltinStructureSets.MINESHAFTS.location()),
+            Map.entry("nether_fortresses", id("fortresses")),
+            Map.entry("strongholds", BuiltinStructureSets.STRONGHOLDS.location()),
+            Map.entry("villages", BuiltinStructureSets.VILLAGES.location()),
+            Map.entry("trial_chambers", BuiltinStructureSets.TRIAL_CHAMBERS.location()),
+            Map.entry("bastions", id("bastions")),
+            Map.entry("buried_treasure", BuiltinStructureSets.BURIED_TREASURES.location()),
+            Map.entry("shipwrecks", BuiltinStructureSets.SHIPWRECKS.location()),
+            Map.entry("ocean_ruins", BuiltinStructureSets.OCEAN_RUINS.location()),
+            Map.entry("pillager_outposts", BuiltinStructureSets.PILLAGER_OUTPOSTS.location()),
+            Map.entry("ruined_portals", BuiltinStructureSets.RUINED_PORTALS.location()),
+            Map.entry("nether_fossils", BuiltinStructureSets.NETHER_FOSSILS.location()),
+            Map.entry("ancient_cities", BuiltinStructureSets.ANCIENT_CITIES.location()),
+            Map.entry("trail_ruins", BuiltinStructureSets.TRAIL_RUINS.location()));
+
+    private AgeStructureGameTests() {}
+
+    @GameTest(template = "empty")
+    public static void structurePagesGateDistinctVanillaSets(GameTestHelper helper) {
+        var lookup = helper.getLevel().registryAccess().lookupOrThrow(Registries.STRUCTURE_SET);
+        for (var entry : SETS.entrySet()) {
+            var setKey = ResourceKey.create(Registries.STRUCTURE_SET, entry.getValue());
+            helper.assertTrue(lookup.get(setKey).isPresent(), entry.getKey() + " needs a registered structure set");
+            var filtered = AgeStructureSelection.filteredLookup(lookup,
+                    List.of(new AgeFeatureSelection.Choice(id(entry.getKey()), Optional.empty())));
+            helper.assertTrue(filtered.get(setKey).isPresent(), entry.getKey() + " must enable its structure set");
+            helper.assertTrue(filtered.get(ResourceKey.create(Registries.STRUCTURE_SET,
+                    BuiltinStructureSets.NETHER_COMPLEXES.location())).isEmpty(),
+                    "Vanilla Nether complexes must stay disabled to keep fortresses and bastions separate");
+            for (var other : SETS.entrySet()) {
+                if (other.getKey().equals(entry.getKey())) continue;
+                helper.assertTrue(filtered.get(ResourceKey.create(Registries.STRUCTURE_SET,
+                        other.getValue())).isEmpty(),
+                        entry.getKey() + " must not enable " + other.getKey());
+            }
+        }
+        helper.assertTrue(AgeStructureSelection.filteredLookup(lookup, List.of()).listElements()
+                        .noneMatch(holder -> SETS.containsValue(holder.key().location())),
+                "An Age without structure pages must not inherit these structures from vanilla biomes");
+        helper.succeed();
+    }
+
+    @GameTest(template = "empty")
+    public static void authoredPagesPersistAndRejectIncompatibleTerrain(GameTestHelper helper) {
+        var registries = helper.getLevel().registryAccess();
+        OrderedWriting written = new OrderedWriting(List.of(WritingEntry.linkPanel(), page("terrain/standard"),
+                page("biome/plains"), page("biome/single"), page("feature/mineshafts"),
+                page("feature/villages"), page("feature/trial_chambers")));
+        AgeGenerationPlan plan = AgeGenerationPlan.compile(written, 149L, AgeGenerationProfiles.STANDARD,
+                AgeTraits.select(149L), registries);
+        List<AgeFeatureSelection.Choice> expected = AgeFeatureSelection.resolved(plan);
+        helper.assertValueEqual(expected.stream().map(AgeFeatureSelection.Choice::id).toList(),
+                List.of(id("mineshafts"), id("villages"), id("trial_chambers")),
+                "Authored structure pages must retain their order");
+        helper.assertValueEqual(AgeFeatureSelection.resolved(AgeGenerationPlan.load(plan.save())), expected,
+                "Authored structure choices must survive an Age plan reload");
+        var filtered = AgeStructureSelection.filteredLookup(registries.lookupOrThrow(Registries.STRUCTURE_SET), expected);
+        helper.assertTrue(filtered.get(ResourceKey.create(Registries.STRUCTURE_SET,
+                BuiltinStructureSets.VILLAGES.location())).isPresent(), "Village set must be enabled");
+        helper.assertTrue(filtered.get(ResourceKey.create(Registries.STRUCTURE_SET,
+                BuiltinStructureSets.PILLAGER_OUTPOSTS.location())).isEmpty(), "Unwritten outposts must stay disabled");
+        String error = AgeStructureSelection.error(id("bastions"),
+                AgeRuntimeProfiles.profiles().get(id("standard")), null, registries);
+        helper.assertTrue(error != null && error.contains("Cave terrain"),
+                "Bastion page must not silently run on Standard terrain");
+        helper.succeed();
+    }
+
+    private static ResourceLocation id(String path) {
+        return ResourceLocation.fromNamespaceAndPath(Rivencraft.MOD_ID, path);
+    }
+
+    private static WritingEntry page(String path) {
+        return WritingEntry.symbol(new SymbolReference(id(path)));
+    }
+}

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

@@ -0,0 +1,169 @@
+package net.dnorberg.rivencraft.book;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import java.util.Random;
+import java.util.Set;
+import java.util.stream.Stream;
+import net.minecraft.core.Holder;
+import net.minecraft.core.HolderLookup;
+import net.minecraft.core.HolderSet;
+import net.minecraft.core.RegistryAccess;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.resources.ResourceLocation;
+import net.minecraft.tags.TagKey;
+import net.minecraft.world.level.levelgen.structure.BuiltinStructureSets;
+import net.minecraft.world.level.levelgen.structure.StructureSet;
+
+/** Frozen Age structure-page choices and their vanilla structure-set gate. */
+public final class AgeStructureSelection {
+    private static final ResourceLocation FORTRESSES = ResourceLocation.fromNamespaceAndPath("rivencraft", "fortresses");
+    private static final ResourceLocation BASTIONS = ResourceLocation.fromNamespaceAndPath("rivencraft", "bastions");
+    private static final List<ResourceLocation> FEATURES = List.of(
+            id("dungeons"), id("mineshafts"), id("nether_fortresses"), id("strongholds"),
+            id("villages"), id("trial_chambers"), id("bastions"), id("buried_treasure"),
+            id("shipwrecks"), id("ocean_ruins"), id("pillager_outposts"), id("ruined_portals"),
+            id("nether_fossils"), id("ancient_cities"), id("trail_ruins"));
+    private static final Map<ResourceLocation, ResourceLocation> STRUCTURE_SETS = Map.ofEntries(
+            Map.entry(id("mineshafts"), BuiltinStructureSets.MINESHAFTS.location()),
+            Map.entry(id("nether_fortresses"), FORTRESSES),
+            Map.entry(id("strongholds"), BuiltinStructureSets.STRONGHOLDS.location()),
+            Map.entry(id("villages"), BuiltinStructureSets.VILLAGES.location()),
+            Map.entry(id("trial_chambers"), BuiltinStructureSets.TRIAL_CHAMBERS.location()),
+            Map.entry(id("bastions"), BASTIONS),
+            Map.entry(id("buried_treasure"), BuiltinStructureSets.BURIED_TREASURES.location()),
+            Map.entry(id("shipwrecks"), BuiltinStructureSets.SHIPWRECKS.location()),
+            Map.entry(id("ocean_ruins"), BuiltinStructureSets.OCEAN_RUINS.location()),
+            Map.entry(id("pillager_outposts"), BuiltinStructureSets.PILLAGER_OUTPOSTS.location()),
+            Map.entry(id("ruined_portals"), BuiltinStructureSets.RUINED_PORTALS.location()),
+            Map.entry(id("nether_fossils"), BuiltinStructureSets.NETHER_FOSSILS.location()),
+            Map.entry(id("ancient_cities"), BuiltinStructureSets.ANCIENT_CITIES.location()),
+            Map.entry(id("trail_ruins"), BuiltinStructureSets.TRAIL_RUINS.location()));
+    private static final Set<ResourceLocation> CONTROLLED_SETS = Set.of(
+            BuiltinStructureSets.MINESHAFTS.location(), BuiltinStructureSets.NETHER_COMPLEXES.location(),
+            BuiltinStructureSets.STRONGHOLDS.location(), BuiltinStructureSets.VILLAGES.location(),
+            BuiltinStructureSets.TRIAL_CHAMBERS.location(), FORTRESSES, BASTIONS,
+            BuiltinStructureSets.BURIED_TREASURES.location(), BuiltinStructureSets.SHIPWRECKS.location(),
+            BuiltinStructureSets.OCEAN_RUINS.location(), BuiltinStructureSets.PILLAGER_OUTPOSTS.location(),
+            BuiltinStructureSets.RUINED_PORTALS.location(), BuiltinStructureSets.NETHER_FOSSILS.location(),
+            BuiltinStructureSets.ANCIENT_CITIES.location(), BuiltinStructureSets.TRAIL_RUINS.location());
+
+    private AgeStructureSelection() {}
+
+    private static ResourceLocation id(String path) {
+        return ResourceLocation.fromNamespaceAndPath("rivencraft", path);
+    }
+
+    public static boolean feature(ResourceLocation id) {
+        return FEATURES.contains(id);
+    }
+
+    public static boolean dungeons(ResourceLocation id) {
+        return id.equals(id("dungeons"));
+    }
+
+    private static ResourceLocation setId(ResourceLocation feature) {
+        return STRUCTURE_SETS.get(feature);
+    }
+
+    public static String error(ResourceLocation feature, AgeRuntimeProfile profile,
+                               AgeBiomeSelection biomes, RegistryAccess registries) {
+        if (!feature(feature)) return "Unsupported structure feature " + feature;
+        if (profile.terrain() == AgeRuntimeProfile.Terrain.VOID)
+            return "Feature " + feature + " requires terrain, not Void";
+        if (dungeons(feature)) {
+            if (profile.terrain() != AgeRuntimeProfile.Terrain.NOISE)
+                return "Feature " + feature + " needs enclosed noise terrain, not Flat";
+            return placedExists(registries, id("dungeons")) ? null
+                    : "Feature " + feature + " requires missing placed feature rivencraft:dungeons";
+        }
+        if (!feature.equals(id("villages")) && !feature.equals(id("strongholds"))
+                && profile.terrain() != AgeRuntimeProfile.Terrain.NOISE)
+            return "Feature " + feature + " needs noise terrain, not Flat";
+        if (feature.equals(id("nether_fortresses")) || feature.equals(id("bastions"))
+                || feature.equals(id("nether_fossils"))) {
+            if (!AgeBiomeSelection.isCave(profile))
+                return "Feature " + feature + " requires Cave terrain with a Nether biome";
+        } else if (feature.equals(id("villages")) || feature.equals(id("strongholds"))
+                || feature.equals(id("buried_treasure")) || feature.equals(id("shipwrecks"))
+                || feature.equals(id("ocean_ruins")) || feature.equals(id("pillager_outposts"))
+                || feature.equals(id("trail_ruins"))) {
+            if (AgeBiomeSelection.isCave(profile))
+                return "Feature " + feature + " requires surface terrain, not Cave";
+        }
+        ResourceLocation setId = setId(feature);
+        var set = registries.lookupOrThrow(Registries.STRUCTURE_SET)
+                .get(ResourceKey.create(Registries.STRUCTURE_SET, setId));
+        if (set.isEmpty()) return "Feature " + feature + " requires missing structure set " + setId;
+        if (biomes == null) return null;
+        Set<ResourceLocation> selected = Set.copyOf(biomes.biomes());
+        boolean compatible = set.orElseThrow().value().structures().stream()
+                .flatMap(entry -> entry.structure().value().biomes().stream())
+                .map(holder -> holder.unwrapKey().map(ResourceKey::location).orElse(null))
+                .anyMatch(selected::contains);
+        return compatible ? null : "Feature " + feature
+                + " needs at least one biome allowed by structure set " + setId;
+    }
+
+    private static boolean placedExists(RegistryAccess registries, ResourceLocation id) {
+        return registries.lookupOrThrow(Registries.PLACED_FEATURE)
+                .get(ResourceKey.create(Registries.PLACED_FEATURE, id)).isPresent();
+    }
+
+    public static List<AgeFeatureSelection.Choice> randomChoices(long ageSeed, AgeRuntimeProfile profile,
+                                                                   AgeBiomeSelection biomes, RegistryAccess registries) {
+        List<ResourceLocation> eligible = new ArrayList<>(FEATURES.stream()
+                .filter(id -> error(id, profile, biomes, registries) == null).toList());
+        Random random = new Random(ageSeed ^ 0x5354525543545552L);
+        Collections.shuffle(eligible, random);
+        int count = random.nextInt(3);
+        return eligible.stream().limit(count)
+                .map(id -> new AgeFeatureSelection.Choice(id, Optional.empty())).toList();
+    }
+
+    private static Set<ResourceLocation> enabledSets(List<AgeFeatureSelection.Choice> choices) {
+        return choices.stream().filter(choice -> feature(choice.id()) && !dungeons(choice.id()))
+                .map(choice -> setId(choice.id())).collect(java.util.stream.Collectors.toUnmodifiableSet());
+    }
+
+    public static Stream<Holder<StructureSet>> allowedSets(Stream<Holder<StructureSet>> sets,
+                                                            List<AgeFeatureSelection.Choice> choices) {
+        Set<ResourceLocation> enabled = enabledSets(choices);
+        return sets.filter(holder -> holder.unwrapKey()
+                .map(key -> allowed(key.location(), enabled)).orElse(false));
+    }
+
+    public static HolderLookup<StructureSet> filteredLookup(HolderLookup<StructureSet> lookup,
+                                                             List<AgeFeatureSelection.Choice> choices) {
+        Set<ResourceLocation> enabled = enabledSets(choices);
+        return new HolderLookup<>() {
+            @Override
+            public Optional<Holder.Reference<StructureSet>> get(ResourceKey<StructureSet> key) {
+                return allowed(key.location(), enabled) ? lookup.get(key) : Optional.empty();
+            }
+
+            @Override
+            public Optional<HolderSet.Named<StructureSet>> get(TagKey<StructureSet> key) {
+                return lookup.get(key);
+            }
+
+            @Override
+            public Stream<Holder.Reference<StructureSet>> listElements() {
+                return lookup.listElements().filter(holder -> allowed(holder.key().location(), enabled));
+            }
+
+            @Override
+            public Stream<HolderSet.Named<StructureSet>> listTags() {
+                return lookup.listTags();
+            }
+        };
+    }
+
+    private static boolean allowed(ResourceLocation set, Set<ResourceLocation> enabled) {
+        return !CONTROLLED_SETS.contains(set) || enabled.contains(set);
+    }
+}

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

@@ -7,6 +7,7 @@ import java.util.UUID;
 import net.dnorberg.rivencraft.Rivencraft;
 import net.dnorberg.rivencraft.item.PageItem;
 import net.dnorberg.rivencraft.world.AgeFeatureChunkGenerator;
+import net.dnorberg.rivencraft.world.AgeDenseOres;
 import net.dnorberg.rivencraft.writing.OrderedWriting;
 import net.dnorberg.rivencraft.writing.BlockSymbolPages;
 import net.dnorberg.rivencraft.writing.SymbolCatalog;
@@ -33,7 +34,13 @@ public final class FeatureWritingGameTests {
                 "feature/huge_trees", "feature/rocks", "feature/lava_lakes",
                 "feature/surface_lakes", "feature/deep_lakes", "feature/ravines",
                 "feature/floating_islands", "feature/tendrils", "feature/skylands",
-                "feature/spheres", "feature/spikes");
+                "feature/spheres", "feature/spikes", "feature/dungeons",
+                "feature/mineshafts", "feature/nether_fortresses",
+                "feature/strongholds", "feature/villages", "feature/trial_chambers",
+                "feature/bastions", "feature/buried_treasure", "feature/shipwrecks",
+                "feature/ocean_ruins", "feature/pillager_outposts", "feature/ruined_portals",
+                "feature/nether_fossils", "feature/ancient_cities", "feature/trail_ruins",
+                "feature/dense_ores");
         helper.assertTrue(PageItem.bundledCreativeSymbols().containsAll(pages),
                 "Supported feature pages must appear in the creative and JEI symbol feed");
         for (String path : pages) {
@@ -64,7 +71,8 @@ public final class FeatureWritingGameTests {
                     || AgeFeatureSelection.tendrils(choice.id())
                     || AgeFeatureSelection.skylands(choice.id())
                     || AgeFeatureSelection.spheres(choice.id())
-                    || AgeFeatureSelection.spikes(choice.id())) continue;
+                    || AgeFeatureSelection.spikes(choice.id())
+                    || choice.id().equals(AgeDenseOres.ID)) continue;
             var placement = AgeFeatureSelection.placedFeature(choice.id());
             helper.assertTrue(registries.lookupOrThrow(Registries.PLACED_FEATURE)
                             .get(ResourceKey.create(Registries.PLACED_FEATURE, placement)).isPresent(),
@@ -176,7 +184,8 @@ public final class FeatureWritingGameTests {
             List<AgeFeatureSelection.Choice> random = AgeFeatureSelection.randomChoices(seed, caveProfile, registries);
             helper.assertTrue(random.stream().allMatch(choice -> AgeFeatureSelection.tendrils(choice.id())
                             || AgeFeatureSelection.spheres(choice.id())
-                            || AgeFeatureSelection.skylands(choice.id())),
+                            || AgeFeatureSelection.skylands(choice.id())
+                            || AgeStructureSelection.feature(choice.id())),
                     "Cave random Ages must not choose incompatible surface features");
             if (random.stream().anyMatch(choice -> AgeFeatureSelection.tendrils(choice.id()))) found = true;
         }

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

@@ -0,0 +1,30 @@
+package net.dnorberg.rivencraft.mixin;
+
+import net.dnorberg.rivencraft.world.AgeFeatureChunkGenerator;
+import net.dnorberg.rivencraft.world.AgeFlatChunkGenerator;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.resources.ResourceLocation;
+import net.minecraft.util.RandomSource;
+import net.minecraft.world.level.WorldGenLevel;
+import net.minecraft.world.level.chunk.ChunkGenerator;
+import net.minecraft.world.level.levelgen.placement.PlacedFeature;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Redirect;
+
+/** Suppresses biome-default monster rooms only in new Rivencraft Ages. */
+@Mixin(ChunkGenerator.class)
+public abstract class AgeDungeonPlacementMixin {
+    @Redirect(method = "applyBiomeDecoration", at = @At(value = "INVOKE",
+            target = "Lnet/minecraft/world/level/levelgen/placement/PlacedFeature;placeWithBiomeCheck(Lnet/minecraft/world/level/WorldGenLevel;Lnet/minecraft/world/level/chunk/ChunkGenerator;Lnet/minecraft/util/RandomSource;Lnet/minecraft/core/BlockPos;)Z"))
+    private boolean rivencraft$gateAmbientDungeons(PlacedFeature feature, WorldGenLevel level,
+                                                     ChunkGenerator generator, RandomSource random, BlockPos pos) {
+        if ((Object) this instanceof AgeFeatureChunkGenerator || (Object) this instanceof AgeFlatChunkGenerator) {
+            ResourceLocation id = level.registryAccess().registryOrThrow(Registries.PLACED_FEATURE).getKey(feature);
+            if (ResourceLocation.withDefaultNamespace("monster_room").equals(id)
+                    || ResourceLocation.withDefaultNamespace("monster_room_deep").equals(id)) return false;
+        }
+        return feature.placeWithBiomeCheck(level, generator, random, pos);
+    }
+}

src/main/java/net/dnorberg/rivencraft/world/AgeDenseOreGameTests.java

@@ -0,0 +1,99 @@
+package net.dnorberg.rivencraft.world;
+
+import java.util.List;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.book.AgeBiomeSelection;
+import net.dnorberg.rivencraft.book.AgeFeatureSelection;
+import net.dnorberg.rivencraft.book.AgeGenerationPlan;
+import net.dnorberg.rivencraft.book.AgeGenerationProfiles;
+import net.dnorberg.rivencraft.book.AgeRuntimeProfiles;
+import net.dnorberg.rivencraft.book.AgeTraits;
+import net.dnorberg.rivencraft.item.PageItem;
+import net.dnorberg.rivencraft.writing.OrderedWriting;
+import net.dnorberg.rivencraft.writing.SymbolReference;
+import net.dnorberg.rivencraft.writing.WritingEntry;
+import net.minecraft.core.Holder;
+import net.minecraft.gametest.framework.GameTest;
+import net.minecraft.gametest.framework.GameTestHelper;
+import net.minecraft.resources.ResourceLocation;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.levelgen.feature.ConfiguredFeature;
+import net.minecraft.world.level.levelgen.feature.Feature;
+import net.minecraft.world.level.levelgen.feature.configurations.OreConfiguration;
+import net.minecraft.world.level.levelgen.placement.PlacedFeature;
+import net.minecraft.world.level.levelgen.structure.templatesystem.BlockMatchTest;
+import net.neoforged.neoforge.gametest.GameTestHolder;
+import net.neoforged.neoforge.gametest.PrefixGameTestTemplate;
+
+/** Dense Ores remains authored-only and discovers ore configurations without a namespace allow-list. */
+@GameTestHolder(Rivencraft.MOD_ID)
+@PrefixGameTestTemplate(false)
+public final class AgeDenseOreGameTests {
+    private AgeDenseOreGameTests() {}
+
+    @GameTest(template = "empty")
+    public static void denseOresPageCompilesAndPersists(GameTestHelper helper) {
+        var registries = helper.getLevel().registryAccess();
+        helper.assertTrue(PageItem.bundledCreativeSymbols().contains("feature/dense_ores"),
+                "Dense Ores must appear in the Creative and JEI page feed");
+        OrderedWriting writing = new OrderedWriting(List.of(WritingEntry.linkPanel(),
+                page("terrain/standard"), page("biome/plains"), page("biome/single"),
+                page("feature/dense_ores")));
+        AgeGenerationPlan plan = AgeGenerationPlan.compile(writing, 55L, AgeGenerationProfiles.STANDARD,
+                AgeTraits.select(55L), registries);
+        helper.assertValueEqual(AgeFeatureSelection.resolved(plan).stream()
+                        .map(AgeFeatureSelection.Choice::id).toList(), List.of(AgeDenseOres.ID),
+                "Dense Ores must be saved as an authored feature");
+        helper.assertValueEqual(AgeFeatureSelection.resolved(AgeGenerationPlan.load(plan.save())),
+                AgeFeatureSelection.resolved(plan), "Dense Ores must survive Age-plan reload");
+        for (long seed = 0; seed < 32; seed++) {
+            helper.assertTrue(AgeFeatureSelection.randomChoices(seed,
+                            AgeRuntimeProfiles.resolve(id("standard")), registries).stream()
+                            .noneMatch(choice -> choice.id().equals(AgeDenseOres.ID)),
+                    "Random Ages must not roll an authored-only Dense Ores page");
+        }
+        helper.succeed();
+    }
+
+    @GameTest(template = "empty")
+    public static void denseOresRejectsUnsuitableTerrainAndBiome(GameTestHelper helper) {
+        var registries = helper.getLevel().registryAccess();
+        helper.assertTrue(AgeDenseOres.error(AgeRuntimeProfiles.resolve(id("flat")), null, registries)
+                        .contains("noise terrain"), "Flat terrain must reject Dense Ores");
+        helper.assertTrue(AgeDenseOres.error(AgeRuntimeProfiles.resolve(id("void")), null, registries)
+                        .contains("noise terrain"), "Void terrain must reject Dense Ores");
+        helper.assertTrue(AgeDenseOres.error(AgeRuntimeProfiles.resolve(id("standard")),
+                        new AgeBiomeSelection(AgeTraits.BiomeDistribution.SINGLE,
+                                List.of(ResourceLocation.withDefaultNamespace("the_end"))), registries)
+                        .contains("biome with registered ore"),
+                "A biome without ore placements must not accept a no-op Dense Ores page");
+        helper.assertTrue(AgeDenseOres.error(AgeRuntimeProfiles.resolve(id("cave")),
+                new AgeBiomeSelection(AgeTraits.BiomeDistribution.SINGLE,
+                        List.of(ResourceLocation.withDefaultNamespace("nether_wastes"))), registries) == null,
+                "Nether ore placements must qualify for a Cave Age");
+        helper.succeed();
+    }
+
+    @GameTest(template = "empty")
+    public static void recognizesOreTargetsButNotStoneBlobs(GameTestHelper helper) {
+        helper.assertTrue(AgeDenseOres.isOre(ore(Blocks.IRON_ORE.defaultBlockState())),
+                "Any namespace's OreConfiguration yielding an ore block must qualify");
+        helper.assertTrue(!AgeDenseOres.isOre(ore(Blocks.STONE.defaultBlockState())),
+                "Ordinary stone replacement must not be doubled as an ore");
+        helper.succeed();
+    }
+
+    private static Holder<PlacedFeature> ore(net.minecraft.world.level.block.state.BlockState output) {
+        var config = new OreConfiguration(new BlockMatchTest(Blocks.STONE), output, 8);
+        var feature = new ConfiguredFeature<>(Feature.ORE, config);
+        return Holder.direct(new PlacedFeature(Holder.direct(feature), List.of()));
+    }
+
+    private static ResourceLocation id(String path) {
+        return ResourceLocation.fromNamespaceAndPath(Rivencraft.MOD_ID, path);
+    }
+
+    private static WritingEntry page(String path) {
+        return WritingEntry.symbol(new SymbolReference(id(path)));
+    }
+}

src/main/java/net/dnorberg/rivencraft/world/AgeDenseOres.java

@@ -0,0 +1,101 @@
+package net.dnorberg.rivencraft.world;
+
+import java.util.HashSet;
+import java.util.Map;
+import java.util.Set;
+import java.util.TreeMap;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.book.AgeBiomeSelection;
+import net.dnorberg.rivencraft.book.AgeRuntimeProfile;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Holder;
+import net.minecraft.core.RegistryAccess;
+import net.minecraft.core.registries.BuiltInRegistries;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.resources.ResourceLocation;
+import net.minecraft.tags.TagKey;
+import net.minecraft.util.RandomSource;
+import net.minecraft.world.level.WorldGenLevel;
+import net.minecraft.world.level.biome.Biome;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.chunk.ChunkAccess;
+import net.minecraft.world.level.chunk.ChunkGenerator;
+import net.minecraft.world.level.levelgen.feature.configurations.OreConfiguration;
+import net.minecraft.world.level.levelgen.placement.PlacedFeature;
+import net.minecraft.world.level.ChunkPos;
+import net.neoforged.neoforge.common.Tags;
+
+/** Replays eligible biome ore placements once per authored Dense Ores page. */
+public final class AgeDenseOres {
+    public static final ResourceLocation ID = ResourceLocation.fromNamespaceAndPath(Rivencraft.MOD_ID, "dense_ores");
+    public static final TagKey<PlacedFeature> EXTRA_ORES = TagKey.create(Registries.PLACED_FEATURE, ID);
+
+    private AgeDenseOres() {}
+
+    public static String error(AgeRuntimeProfile profile, AgeBiomeSelection biomes, RegistryAccess registries) {
+        if (profile.terrain() != AgeRuntimeProfile.Terrain.NOISE)
+            return "Dense Ores needs noise terrain with replaceable underground stone or netherrack";
+        if (biomes == null) return null;
+        var registry = registries.lookupOrThrow(Registries.BIOME);
+        boolean eligible = biomes.biomes().stream()
+                .map(id -> registry.get(ResourceKey.create(Registries.BIOME, id)))
+                .flatMap(java.util.Optional::stream)
+                .anyMatch(holder -> oreFeatures(holder).stream().anyMatch(AgeDenseOres::isOre));
+        return eligible ? null : "Dense Ores needs at least one biome with registered ore placements";
+    }
+
+    /** Vanilla-style and modded OreConfiguration targets, or an explicit opt-in tag. */
+    public static boolean isOre(Holder<PlacedFeature> holder) {
+        if (holder.is(EXTRA_ORES)) return true;
+        if (!(holder.value().feature().value().config() instanceof OreConfiguration ore)) return false;
+        return ore.targetStates.stream().anyMatch(target -> isOreBlock(target.state));
+    }
+
+    private static boolean isOreBlock(BlockState state) {
+        if (state.is(Tags.Blocks.ORES)) return true;
+        // Some third-party ores omit the common tag; require an ore configuration
+        // as well so similarly named decorative features cannot be selected.
+        String path = BuiltInRegistries.BLOCK.getKey(state.getBlock()).getPath();
+        return path.endsWith("_ore") || path.contains("_ore_");
+    }
+
+    private static java.util.List<Holder<PlacedFeature>> oreFeatures(Holder<Biome> biome) {
+        // A mod may register its ore in a non-vanilla decoration step. Its
+        // configuration and output, not its stage or namespace, decide eligibility.
+        return biome.value().getGenerationSettings().features().stream()
+                .flatMap(net.minecraft.core.HolderSet::stream).toList();
+    }
+
+    public static void place(WorldGenLevel level, ChunkAccess chunk, ChunkGenerator generator,
+                             long ageSeed, int occurrence) {
+        Set<Holder<Biome>> biomes = new HashSet<>();
+        ChunkPos.rangeClosed(chunk.getPos(), 1).forEach(pos -> {
+            for (var section : level.getChunk(pos.x, pos.z).getSections())
+                section.getBiomes().getAll(biomes::add);
+        });
+        biomes.retainAll(generator.getBiomeSource().possibleBiomes());
+        Map<ResourceLocation, PlacedFeature> ores = new TreeMap<>();
+        for (Holder<Biome> biome : biomes) {
+            for (Holder<PlacedFeature> feature : oreFeatures(biome)) {
+                if (!isOre(feature)) continue;
+                feature.unwrapKey().ifPresent(key -> ores.putIfAbsent(key.location(), feature.value()));
+            }
+        }
+        BlockPos origin = new BlockPos(chunk.getPos().getMinBlockX(), level.getMinBuildHeight(),
+                chunk.getPos().getMinBlockZ());
+        for (var entry : ores.entrySet()) {
+            long seed = mix(ageSeed ^ (long) origin.getX() * 341873128712L
+                    ^ (long) origin.getZ() * 132897987541L
+                    ^ (long) entry.getKey().hashCode() * 0x9E3779B97F4A7C15L
+                    ^ (long) occurrence * 0xD1B54A32D192ED03L);
+            entry.getValue().placeWithBiomeCheck(level, generator, RandomSource.create(seed), origin);
+        }
+    }
+
+    private static long mix(long value) {
+        value = (value ^ value >>> 30) * 0xBF58476D1CE4E5B9L;
+        value = (value ^ value >>> 27) * 0x94D049BB133111EBL;
+        return value ^ value >>> 31;
+    }
+}

src/main/java/net/dnorberg/rivencraft/world/AgeFeatureChunkGenerator.java

@@ -8,6 +8,8 @@ import java.util.List;
 import java.util.Map;
 import java.util.concurrent.CompletableFuture;
 import net.dnorberg.rivencraft.book.AgeFeatureSelection;
+import net.dnorberg.rivencraft.book.AgeStructureSelection;
+import net.minecraft.core.HolderLookup;
 import net.minecraft.world.level.levelgen.Heightmap;
 import net.minecraft.core.BlockPos;
 import net.minecraft.core.Holder;
@@ -25,6 +27,7 @@ import net.minecraft.world.level.biome.BiomeManager;
 import net.minecraft.world.level.biome.BiomeSource;
 import net.minecraft.world.level.chunk.ChunkAccess;
 import net.minecraft.world.level.chunk.ChunkGenerator;
+import net.minecraft.world.level.chunk.ChunkGeneratorStructureState;
 import net.minecraft.world.level.chunk.ProtoChunk;
 import net.minecraft.world.level.levelgen.GenerationStep;
 import net.minecraft.world.level.levelgen.LegacyRandomSource;
@@ -37,6 +40,7 @@ import net.minecraft.world.level.levelgen.carver.CarvingContext;
 import net.minecraft.world.level.levelgen.carver.ConfiguredWorldCarver;
 import net.minecraft.world.level.levelgen.placement.BiomeFilter;
 import net.minecraft.world.level.levelgen.placement.PlacedFeature;
+import net.minecraft.world.level.levelgen.structure.StructureSet;
 import net.minecraft.world.level.levelgen.placement.RarityFilter;
 import net.minecraft.world.level.levelgen.feature.ConfiguredFeature;
 import net.minecraft.world.level.levelgen.feature.Feature;
@@ -71,6 +75,12 @@ public final class AgeFeatureChunkGenerator extends NoiseBasedChunkGenerator {
     @Override
     protected MapCodec<? extends ChunkGenerator> codec() { return CODEC; }
 
+    @Override
+    public ChunkGeneratorStructureState createState(HolderLookup<StructureSet> sets, RandomState random, long seed) {
+        return ChunkGeneratorStructureState.createForNormal(random, seed, getBiomeSource(),
+                AgeStructureSelection.filteredLookup(sets, features));
+    }
+
     @Override
     public CompletableFuture<ChunkAccess> fillFromNoise(Blender blender, RandomState random,
                                                          StructureManager structures, ChunkAccess chunk) {
@@ -160,6 +170,10 @@ public final class AgeFeatureChunkGenerator extends NoiseBasedChunkGenerator {
                         spikeOccurrences.merge(choice.id(), 1, Integer::sum) - 1);
                 continue;
             }
+            if (choice.id().equals(AgeDenseOres.ID)) {
+                AgeDenseOres.place(level, chunk, this, ageSeed, occurrence);
+                continue;
+            }
             if (AgeFeatureSelection.surfaceVegetation(choice.id())) {
                 int surface = chunk.getHeight(Heightmap.Types.WORLD_SURFACE_WG, 8, 8);
                 if (!AgeFeatureSelection.supportsSurfaceVegetation(

src/main/java/net/dnorberg/rivencraft/world/AgeFlatChunkGenerator.java

@@ -9,6 +9,7 @@ import java.util.Map;
 import java.util.concurrent.CompletableFuture;
 import java.util.stream.Stream;
 import net.dnorberg.rivencraft.book.AgeFeatureSelection;
+import net.dnorberg.rivencraft.book.AgeStructureSelection;
 import net.minecraft.Util;
 import net.minecraft.core.BlockPos;
 import net.minecraft.core.Holder;
@@ -71,7 +72,8 @@ public final class AgeFlatChunkGenerator extends ChunkGenerator {
         Stream<Holder<StructureSet>> entries = settings.structureOverrides()
                 .map(HolderSet::stream)
                 .orElseGet(() -> structures.listElements().map(holder -> (Holder<StructureSet>) holder));
-        return ChunkGeneratorStructureState.createForFlat(random, seed, biomeSource, entries);
+        return ChunkGeneratorStructureState.createForFlat(random, seed, biomeSource,
+                AgeStructureSelection.allowedSets(entries, features));
     }
 
     @Override

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

@@ -253,6 +253,38 @@
   "symbol.rivencraft.feature.spheres.description": "Add wandering chains of solid spheres through the Age, with a random or selected block material.",
   "symbol.rivencraft.feature.spikes": "Spikes",
   "symbol.rivencraft.feature.spikes.description": "Add rare rising spikes on exposed solid ground, with a random or selected block material.",
+  "symbol.rivencraft.feature.dungeons": "Dungeons",
+  "symbol.rivencraft.feature.dungeons.description": "Add monster-room dungeons below ground in this Age.",
+  "symbol.rivencraft.feature.mineshafts": "Mineshafts",
+  "symbol.rivencraft.feature.mineshafts.description": "Allow abandoned mineshafts in compatible terrain and biomes.",
+  "symbol.rivencraft.feature.nether_fortresses": "Nether Fortresses",
+  "symbol.rivencraft.feature.nether_fortresses.description": "Allow Nether fortresses in a Cave Age with a compatible Nether biome.",
+  "symbol.rivencraft.feature.strongholds": "Strongholds",
+  "symbol.rivencraft.feature.strongholds.description": "Allow strongholds with End portal rooms in a compatible Age.",
+  "symbol.rivencraft.feature.villages": "Villages",
+  "symbol.rivencraft.feature.villages.description": "Allow biome-appropriate villages on surface terrain.",
+  "symbol.rivencraft.feature.trial_chambers": "Trial Chambers",
+  "symbol.rivencraft.feature.trial_chambers.description": "Allow underground Trial Chambers in compatible Minecraft 1.21.1 biomes.",
+  "symbol.rivencraft.feature.bastions": "Bastion Remnants",
+  "symbol.rivencraft.feature.bastions.description": "Allow Bastion Remnants in a Cave Age with a compatible Nether biome.",
+  "symbol.rivencraft.feature.buried_treasure": "Buried Treasure",
+  "symbol.rivencraft.feature.buried_treasure.description": "Allow buried treasure beneath compatible beaches.",
+  "symbol.rivencraft.feature.shipwrecks": "Shipwrecks",
+  "symbol.rivencraft.feature.shipwrecks.description": "Allow shipwrecks in compatible ocean and beach biomes.",
+  "symbol.rivencraft.feature.ocean_ruins": "Ocean Ruins",
+  "symbol.rivencraft.feature.ocean_ruins.description": "Allow warm and cold ocean ruins in compatible biomes.",
+  "symbol.rivencraft.feature.pillager_outposts": "Pillager Outposts",
+  "symbol.rivencraft.feature.pillager_outposts.description": "Allow pillager outposts in compatible surface biomes.",
+  "symbol.rivencraft.feature.ruined_portals": "Ruined Portals",
+  "symbol.rivencraft.feature.ruined_portals.description": "Allow ruined portals in compatible surface or Nether biomes.",
+  "symbol.rivencraft.feature.nether_fossils": "Nether Fossils",
+  "symbol.rivencraft.feature.nether_fossils.description": "Allow Nether fossils in a Cave Age with a compatible Nether biome.",
+  "symbol.rivencraft.feature.ancient_cities": "Ancient Cities",
+  "symbol.rivencraft.feature.ancient_cities.description": "Allow ancient cities in compatible Deep Dark biomes.",
+  "symbol.rivencraft.feature.trail_ruins": "Trail Ruins",
+  "symbol.rivencraft.feature.trail_ruins.description": "Allow buried trail ruins in compatible surface biomes.",
+  "symbol.rivencraft.feature.dense_ores": "Dense Ores",
+  "symbol.rivencraft.feature.dense_ores.description": "Repeat compatible vanilla and modded ore placements once per page in this Age.",
   "symbol.rivencraft.feature.lava_lakes": "Small Lakes",
   "symbol.rivencraft.feature.lava_lakes.description": "Add small surface lakes using a random fluid, or specify one with a fluid page.",
   "generator.rivencraft.standard": "Standard",

src/main/resources/data/rivencraft/rivencraft/symbols/feature/ancient_cities.json

@@ -0,0 +1,8 @@
+{
+  "schema_version": 2,
+  "name": "symbol.rivencraft.feature.ancient_cities",
+  "description": "symbol.rivencraft.feature.ancient_cities.description",
+  "category": "rivencraft:feature",
+  "semantics": { "role": "feature", "value": "rivencraft:ancient_cities" },
+  "poem": "Civilization Darkness Silence Ancient"
+}

src/main/resources/data/rivencraft/rivencraft/symbols/feature/bastions.json

@@ -0,0 +1,8 @@
+{
+  "schema_version": 2,
+  "name": "symbol.rivencraft.feature.bastions",
+  "description": "symbol.rivencraft.feature.bastions.description",
+  "category": "rivencraft:feature",
+  "semantics": { "role": "feature", "value": "rivencraft:bastions" },
+  "poem": "Civilization Ruin Greed Nether"
+}

src/main/resources/data/rivencraft/rivencraft/symbols/feature/buried_treasure.json

@@ -0,0 +1,8 @@
+{
+  "schema_version": 2,
+  "name": "symbol.rivencraft.feature.buried_treasure",
+  "description": "symbol.rivencraft.feature.buried_treasure.description",
+  "category": "rivencraft:feature",
+  "semantics": { "role": "feature", "value": "rivencraft:buried_treasure" },
+  "poem": "Treasure Sand Ocean Memory"
+}

src/main/resources/data/rivencraft/rivencraft/symbols/feature/dense_ores.json

@@ -0,0 +1,8 @@
+{
+  "schema_version": 2,
+  "name": "symbol.rivencraft.feature.dense_ores",
+  "description": "symbol.rivencraft.feature.dense_ores.description",
+  "category": "rivencraft:feature",
+  "semantics": { "role": "feature", "value": "rivencraft:dense_ores" },
+  "poem": "Nature Material Treasure Abundance"
+}

src/main/resources/data/rivencraft/rivencraft/symbols/feature/dungeons.json

@@ -0,0 +1,8 @@
+{
+  "schema_version": 2,
+  "name": "symbol.rivencraft.feature.dungeons",
+  "description": "symbol.rivencraft.feature.dungeons.description",
+  "category": "rivencraft:feature",
+  "semantics": { "role": "feature", "value": "rivencraft:dungeons" },
+  "poem": "Civilization Constraint Chain Resurrect"
+}

src/main/resources/data/rivencraft/rivencraft/symbols/feature/mineshafts.json

@@ -0,0 +1,8 @@
+{
+  "schema_version": 2,
+  "name": "symbol.rivencraft.feature.mineshafts",
+  "description": "symbol.rivencraft.feature.mineshafts.description",
+  "category": "rivencraft:feature",
+  "semantics": { "role": "feature", "value": "rivencraft:mineshafts" },
+  "poem": "Civilization Machine Motion Tradition"
+}

src/main/resources/data/rivencraft/rivencraft/symbols/feature/nether_fortresses.json

@@ -0,0 +1,8 @@
+{
+  "schema_version": 2,
+  "name": "symbol.rivencraft.feature.nether_fortresses",
+  "description": "symbol.rivencraft.feature.nether_fortresses.description",
+  "category": "rivencraft:feature",
+  "semantics": { "role": "feature", "value": "rivencraft:nether_fortresses" },
+  "poem": "Civilization Machine Power Entropy"
+}

src/main/resources/data/rivencraft/rivencraft/symbols/feature/nether_fossils.json

@@ -0,0 +1,8 @@
+{
+  "schema_version": 2,
+  "name": "symbol.rivencraft.feature.nether_fossils",
+  "description": "symbol.rivencraft.feature.nether_fossils.description",
+  "category": "rivencraft:feature",
+  "semantics": { "role": "feature", "value": "rivencraft:nether_fossils" },
+  "poem": "Bone Death Nether Time"
+}

src/main/resources/data/rivencraft/rivencraft/symbols/feature/ocean_ruins.json

@@ -0,0 +1,8 @@
+{
+  "schema_version": 2,
+  "name": "symbol.rivencraft.feature.ocean_ruins",
+  "description": "symbol.rivencraft.feature.ocean_ruins.description",
+  "category": "rivencraft:feature",
+  "semantics": { "role": "feature", "value": "rivencraft:ocean_ruins" },
+  "poem": "Ocean Stone Ruin Time"
+}

src/main/resources/data/rivencraft/rivencraft/symbols/feature/pillager_outposts.json

@@ -0,0 +1,8 @@
+{
+  "schema_version": 2,
+  "name": "symbol.rivencraft.feature.pillager_outposts",
+  "description": "symbol.rivencraft.feature.pillager_outposts.description",
+  "category": "rivencraft:feature",
+  "semantics": { "role": "feature", "value": "rivencraft:pillager_outposts" },
+  "poem": "Civilization Conflict Watchtower Danger"
+}

src/main/resources/data/rivencraft/rivencraft/symbols/feature/ruined_portals.json

@@ -0,0 +1,8 @@
+{
+  "schema_version": 2,
+  "name": "symbol.rivencraft.feature.ruined_portals",
+  "description": "symbol.rivencraft.feature.ruined_portals.description",
+  "category": "rivencraft:feature",
+  "semantics": { "role": "feature", "value": "rivencraft:ruined_portals" },
+  "poem": "Portal Ruin Flame Memory"
+}

src/main/resources/data/rivencraft/rivencraft/symbols/feature/shipwrecks.json

@@ -0,0 +1,8 @@
+{
+  "schema_version": 2,
+  "name": "symbol.rivencraft.feature.shipwrecks",
+  "description": "symbol.rivencraft.feature.shipwrecks.description",
+  "category": "rivencraft:feature",
+  "semantics": { "role": "feature", "value": "rivencraft:shipwrecks" },
+  "poem": "Ocean Journey Ruin Timber"
+}

src/main/resources/data/rivencraft/rivencraft/symbols/feature/strongholds.json

@@ -0,0 +1,8 @@
+{
+  "schema_version": 2,
+  "name": "symbol.rivencraft.feature.strongholds",
+  "description": "symbol.rivencraft.feature.strongholds.description",
+  "category": "rivencraft:feature",
+  "semantics": { "role": "feature", "value": "rivencraft:strongholds" },
+  "poem": "Civilization Wisdom Future Honor"
+}

src/main/resources/data/rivencraft/rivencraft/symbols/feature/trail_ruins.json

@@ -0,0 +1,8 @@
+{
+  "schema_version": 2,
+  "name": "symbol.rivencraft.feature.trail_ruins",
+  "description": "symbol.rivencraft.feature.trail_ruins.description",
+  "category": "rivencraft:feature",
+  "semantics": { "role": "feature", "value": "rivencraft:trail_ruins" },
+  "poem": "Civilization Buried Path Memory"
+}

src/main/resources/data/rivencraft/rivencraft/symbols/feature/trial_chambers.json

@@ -0,0 +1,8 @@
+{
+  "schema_version": 2,
+  "name": "symbol.rivencraft.feature.trial_chambers",
+  "description": "symbol.rivencraft.feature.trial_chambers.description",
+  "category": "rivencraft:feature",
+  "semantics": { "role": "feature", "value": "rivencraft:trial_chambers" },
+  "poem": "Civilization Trial Structure Challenge"
+}

src/main/resources/data/rivencraft/rivencraft/symbols/feature/villages.json

@@ -0,0 +1,8 @@
+{
+  "schema_version": 2,
+  "name": "symbol.rivencraft.feature.villages",
+  "description": "symbol.rivencraft.feature.villages.description",
+  "category": "rivencraft:feature",
+  "semantics": { "role": "feature", "value": "rivencraft:villages" },
+  "poem": "Civilization Society Harmony Nurture"
+}

src/main/resources/data/rivencraft/tags/worldgen/placed_feature/dense_ores.json

@@ -0,0 +1,4 @@
+{
+  "replace": false,
+  "values": []
+}

src/main/resources/data/rivencraft/worldgen/placed_feature/dungeons.json

@@ -0,0 +1,15 @@
+{
+  "feature": "minecraft:monster_room",
+  "placement": [
+    { "type": "minecraft:count", "count": 8 },
+    { "type": "minecraft:in_square" },
+    {
+      "type": "minecraft:height_range",
+      "height": {
+        "type": "minecraft:uniform",
+        "min_inclusive": { "above_bottom": 1 },
+        "max_inclusive": { "below_top": 1 }
+      }
+    }
+  ]
+}

src/main/resources/data/rivencraft/worldgen/structure_set/bastions.json

@@ -0,0 +1,11 @@
+{
+  "structures": [
+    { "structure": "minecraft:bastion_remnant", "weight": 1 }
+  ],
+  "placement": {
+    "type": "minecraft:random_spread",
+    "spacing": 27,
+    "separation": 4,
+    "salt": 30084233
+  }
+}

src/main/resources/data/rivencraft/worldgen/structure_set/fortresses.json

@@ -0,0 +1,11 @@
+{
+  "structures": [
+    { "structure": "minecraft:fortress", "weight": 1 }
+  ],
+  "placement": {
+    "type": "minecraft:random_spread",
+    "spacing": 27,
+    "separation": 4,
+    "salt": 30084232
+  }
+}

src/main/resources/rivencraft.mixins.json

@@ -3,6 +3,9 @@
   "minVersion": "0.8",
   "package": "net.dnorberg.rivencraft.mixin",
   "compatibilityLevel": "JAVA_21",
+  "mixins": [
+    "AgeDungeonPlacementMixin"
+  ],
   "client": [
     "client.ClientLevelSoundMixin",
     "client.ImmersivePortalsGuiRenderingMixin",