diff --git a/gradle.properties b/gradle.properties
index a1b2daa..8c8bc40 100644
--- a/gradle.properties
+++ b/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=1.0.0.2
+mod_version=1.0.1.1
 immersive_portals_version=6.0.7
 terrablender_version=4.1.0.8
 serene_seasons_version_id=pHEgQQUE
diff --git a/src/main/java/net/dnorberg/rivencraft/book/AgeBiomeSelection.java b/src/main/java/net/dnorberg/rivencraft/book/AgeBiomeSelection.java
index 0ed8b6c..ad053c2 100644
--- a/src/main/java/net/dnorberg/rivencraft/book/AgeBiomeSelection.java
+++ b/src/main/java/net/dnorberg/rivencraft/book/AgeBiomeSelection.java
@@ -8,6 +8,7 @@ import java.util.Random;
 import java.util.Set;
 import net.dnorberg.rivencraft.Rivencraft;
 import net.dnorberg.rivencraft.compat.TerraBlenderBiomes;
+import net.dnorberg.rivencraft.writing.BiomeSymbolPages;
 import net.dnorberg.rivencraft.writing.SymbolSemantics;
 import net.dnorberg.rivencraft.writing.WritingGrammar;
 import net.minecraft.core.Holder;
@@ -34,6 +35,12 @@ public record AgeBiomeSelection(AgeTraits.BiomeDistribution distribution, List<R
 
     public static AgeBiomeSelection compile(WritingGrammar.Result writing, AgeTraits traits,
                                              AgeRuntimeProfile profile, long seed, RegistryAccess registries) {
+        return compile(writing, traits, profile, seed, registries, RandomPagePolicy.UNRESTRICTED);
+    }
+
+    public static AgeBiomeSelection compile(WritingGrammar.Result writing, AgeTraits traits,
+                                             AgeRuntimeProfile profile, long seed, RegistryAccess registries,
+                                             RandomPagePolicy policy) {
         List<ResourceLocation> authored = writing.symbols().stream()
                 .filter(symbol -> symbol.semantics().role() == SymbolSemantics.Role.BIOME)
                 .map(symbol -> ((SymbolSemantics.ResourceValue) symbol.semantics().value()).id()).toList();
@@ -67,10 +74,26 @@ public record AgeBiomeSelection(AgeTraits.BiomeDistribution distribution, List<R
                         + " or a TerraBlender Nether region");
             }
         }
-        List<ResourceLocation> availableBiomes = eligible(registries, profile);
-        if (availableBiomes.isEmpty()) throw new IllegalArgumentException("No eligible biomes for terrain " + profile.noiseSettings());
+        List<ResourceLocation> terrainBiomes = eligible(registries, profile);
+        if (terrainBiomes.isEmpty()) throw new IllegalArgumentException("No eligible biomes for terrain " + profile.noiseSettings());
+        List<ResourceLocation> availableBiomes = distribution == AgeTraits.BiomeDistribution.NATIVE
+                ? terrainBiomes : new ArrayList<>(policy.eligible(terrainBiomes, BiomeSymbolPages::symbolId));
+        if (distribution != AgeTraits.BiomeDistribution.NATIVE
+                && new LinkedHashSet<>(availableBiomes).size() < minimum(distribution)) {
+            ResourceLocation preferred = profile.terrain() == AgeRuntimeProfile.Terrain.VOID
+                    ? ResourceLocation.withDefaultNamespace("the_void")
+                    : cave ? ResourceLocation.withDefaultNamespace("deep_dark")
+                    : ResourceLocation.withDefaultNamespace("plains");
+            if (terrainBiomes.contains(preferred) && !availableBiomes.contains(preferred))
+                availableBiomes.add(preferred);
+            for (ResourceLocation fallback : terrainBiomes) {
+                if (new LinkedHashSet<>(availableBiomes).size() >= minimum(distribution)) break;
+                if (!availableBiomes.contains(fallback)) availableBiomes.add(fallback);
+            }
+        }
         if (distribution == AgeTraits.BiomeDistribution.NATIVE) {
             if (!authored.isEmpty()) throw new IllegalArgumentException("Native biome distribution cannot use biome pages");
+            // Native noise biomes are supplied by Minecraft's preset, not chosen as Pages.
             return new AgeBiomeSelection(distribution, profile.terrain() == AgeRuntimeProfile.Terrain.FLAT
                     ? List.of(ResourceLocation.withDefaultNamespace("plains"))
                     : isCave(profile) ? availableBiomes : presetBiomes(registries, profile));
diff --git a/src/main/java/net/dnorberg/rivencraft/book/AgeDefinition.java b/src/main/java/net/dnorberg/rivencraft/book/AgeDefinition.java
index 7f279f4..ef030b0 100644
--- a/src/main/java/net/dnorberg/rivencraft/book/AgeDefinition.java
+++ b/src/main/java/net/dnorberg/rivencraft/book/AgeDefinition.java
@@ -23,7 +23,8 @@ public record AgeDefinition(
         @Nullable AgeSeasonMode seasonMode,
         List<AgeFeatureSelection.Choice> randomFeatures,
         AgeInstability instability,
-        AgeInstabilityPlan instabilityPlan
+        AgeInstabilityPlan instabilityPlan,
+        RandomPagePolicy randomPagePolicy
 ) {
     public static final ResourceLocation RANDOM_VANILLA_PROFILE = ResourceLocation.fromNamespaceAndPath(
             Rivencraft.MOD_ID, "random_vanilla"
@@ -39,6 +40,7 @@ public record AgeDefinition(
         Objects.requireNonNull(traits, "traits");
         Objects.requireNonNull(instability, "instability");
         Objects.requireNonNull(instabilityPlan, "instabilityPlan");
+        Objects.requireNonNull(randomPagePolicy, "randomPagePolicy");
         randomFeatures = List.copyOf(randomFeatures);
         if (plan != null && !randomFeatures.isEmpty()) {
             throw new IllegalArgumentException("Authored Ages cannot also have random features");
@@ -88,6 +90,16 @@ public record AgeDefinition(
                 AgeInstabilityPlan.empty());
     }
 
+    public AgeDefinition(UUID id, String name, long seed, ResourceLocation generationProfile,
+                         int generationVersion, long createdGameTime, ResourceLocation dimensionId,
+                         BlockPos spawn, AgeTraits traits, AgeGenerationPlan plan,
+                         @Nullable AgeSeasonMode seasonMode, List<AgeFeatureSelection.Choice> randomFeatures,
+                         AgeInstability instability, AgeInstabilityPlan instabilityPlan) {
+        this(id, name, seed, generationProfile, generationVersion, createdGameTime,
+                dimensionId, spawn, traits, plan, seasonMode, randomFeatures, instability,
+                instabilityPlan, RandomPagePolicy.UNRESTRICTED);
+    }
+
     public static ResourceLocation dimensionId(UUID ageId) {
         return ResourceLocation.fromNamespaceAndPath(Rivencraft.MOD_ID, "age/" + ageId);
     }
@@ -117,7 +129,7 @@ public record AgeDefinition(
     public AgeDefinition withSpawn(BlockPos spawn) {
         return new AgeDefinition(id, name, seed, generationProfile, generationVersion,
                 createdGameTime, dimensionId, spawn.immutable(), traits, plan, seasonMode,
-                randomFeatures, instability, instabilityPlan);
+                randomFeatures, instability, instabilityPlan, randomPagePolicy);
     }
 
     /** A frozen authored profile takes precedence over the profile ID on old books. */
diff --git a/src/main/java/net/dnorberg/rivencraft/book/AgeDimensionService.java b/src/main/java/net/dnorberg/rivencraft/book/AgeDimensionService.java
index 77ddc66..1029813 100644
--- a/src/main/java/net/dnorberg/rivencraft/book/AgeDimensionService.java
+++ b/src/main/java/net/dnorberg/rivencraft/book/AgeDimensionService.java
@@ -465,7 +465,7 @@ public final class AgeDimensionService {
         AgeBiomeSelection selection = age.plan() != null && age.plan().biomeSelection() != null
                 ? age.plan().biomeSelection()
                 : AgeBiomeSelection.compile(net.dnorberg.rivencraft.writing.WritingGrammar.parse(OrderedWriting.EMPTY),
-                        age.traits(), profile, age.seed(), server.registryAccess());
+                        age.traits(), profile, age.seed(), server.registryAccess(), age.randomPagePolicy());
         var registry = server.registryAccess().lookupOrThrow(Registries.BIOME);
         List<Holder<Biome>> biomes = new ArrayList<>();
         List<ResourceLocation> fallbacks = AgeBiomeSelection.eligible(server.registryAccess(), profile);
diff --git a/src/main/java/net/dnorberg/rivencraft/book/AgeFeatureSelection.java b/src/main/java/net/dnorberg/rivencraft/book/AgeFeatureSelection.java
index 3cf892b..d773c1d 100644
--- a/src/main/java/net/dnorberg/rivencraft/book/AgeFeatureSelection.java
+++ b/src/main/java/net/dnorberg/rivencraft/book/AgeFeatureSelection.java
@@ -158,12 +158,19 @@ public final class AgeFeatureSelection {
 
     /** Page-free Ages roll up to two material features, plus rare Skylands, once at creation. */
     public static List<Choice> randomChoices(long ageSeed, AgeRuntimeProfile profile, RegistryAccess registries) {
+        return randomChoices(ageSeed, profile, registries, RandomPagePolicy.UNRESTRICTED);
+    }
+
+    public static List<Choice> randomChoices(long ageSeed, AgeRuntimeProfile profile, RegistryAccess registries,
+                                             RandomPagePolicy policy) {
         Random random = new Random(ageSeed ^ 0x4D4154455249414CL);
         int count = random.nextInt(3);
         List<LegacyRankChoice.Option<ResourceLocation>> features = new ArrayList<>();
-        for (ResourceLocation id : BLOCK_FEATURES) if (error(id, profile, registries) == null)
+        for (ResourceLocation id : BLOCK_FEATURES) if (error(id, profile, registries) == null
+                && policy.allows(featurePage(id)))
             features.add(new LegacyRankChoice.Option<>(id, randomMaterialRank(id)));
-        for (ResourceLocation id : FLUID_FEATURES) if (error(id, profile, registries) == null)
+        for (ResourceLocation id : FLUID_FEATURES) if (error(id, profile, registries) == null
+                && policy.allows(featurePage(id)))
             features.add(new LegacyRankChoice.Option<>(id, randomMaterialRank(id)));
         List<Choice> choices = new ArrayList<>();
         while (choices.size() < count && !features.isEmpty()) {
@@ -172,23 +179,30 @@ public final class AgeFeatureSelection {
             var category = solidFeature(feature)
                     ? BlockSymbolPages.CATEGORY : BlockSymbolPages.FLUID_CATEGORY;
             List<ResourceLocation> materials = BlockSymbolPages.availableBlocks(category).stream()
+                    .filter(id -> policy.allows(BlockSymbolPages.symbolId(id)))
                     .filter(id -> materialError(new Choice(feature, Optional.of(id))) == null).toList();
             if (!materials.isEmpty()) choices.add(new Choice(feature,
                     Optional.of(materials.get(random.nextInt(materials.size())))));
         }
         if (profile.terrain() == AgeRuntimeProfile.Terrain.NOISE
+                && policy.allows(featurePage(id("skylands")))
                 && Math.floorMod(mix(ageSeed ^ RANDOM_SKYLANDS_SALT), 8) == 0)
             choices.add(new Choice(id("skylands"), Optional.empty()));
-        if (error(CRYSTAL_FORMATIONS, profile, registries) == null && random.nextInt(10) == 0)
+        if (error(CRYSTAL_FORMATIONS, profile, registries) == null
+                && policy.allows(featurePage(CRYSTAL_FORMATIONS)) && random.nextInt(10) == 0)
             choices.add(new Choice(CRYSTAL_FORMATIONS, Optional.empty()));
-        if (randomStarFissure(ageSeed))
+        if (policy.allows(featurePage(STAR_FISSURES)) && randomStarFissure(ageSeed))
             choices.add(new Choice(STAR_FISSURES, Optional.empty()));
         AgeBiomeSelection biomes = AgeBiomeSelection.compile(WritingGrammar.parse(OrderedWriting.EMPTY),
-                AgeTraits.select(ageSeed), profile, ageSeed, registries);
-        choices.addAll(AgeStructureSelection.randomChoices(ageSeed, profile, biomes, registries));
+                AgeTraits.select(ageSeed, policy), profile, ageSeed, registries, policy);
+        choices.addAll(AgeStructureSelection.randomChoices(ageSeed, profile, biomes, registries, policy));
         return List.copyOf(choices);
     }
 
+    private static ResourceLocation featurePage(ResourceLocation id) {
+        return ResourceLocation.fromNamespaceAndPath("rivencraft", "feature/" + id.getPath());
+    }
+
     static int randomMaterialRank(ResourceLocation feature) {
         if (feature.equals(id("surface_lakes")) || feature.equals(id("deep_lakes"))) return 1;
         if (feature.equals(id("lava_lakes"))) return 2; // New separate fluid choice.
diff --git a/src/main/java/net/dnorberg/rivencraft/book/AgeInstability.java b/src/main/java/net/dnorberg/rivencraft/book/AgeInstability.java
index c4874f4..09b88d9 100644
--- a/src/main/java/net/dnorberg/rivencraft/book/AgeInstability.java
+++ b/src/main/java/net/dnorberg/rivencraft/book/AgeInstability.java
@@ -56,6 +56,11 @@ public record AgeInstability(int version, int score, List<Contribution> breakdow
     }
 
     static AgeInstability compute(AgeGenerationPlan plan, AgeTraits traits, RegistryAccess registries, long ageSeed) {
+        return compute(plan, traits, registries, ageSeed, RandomPagePolicy.UNRESTRICTED);
+    }
+
+    static AgeInstability compute(AgeGenerationPlan plan, AgeTraits traits, RegistryAccess registries,
+                                  long ageSeed, RandomPagePolicy policy) {
         Objects.requireNonNull(traits, "traits");
         List<Contribution> contributions = new ArrayList<>();
         if (plan == null) {
@@ -87,7 +92,7 @@ public record AgeInstability(int version, int score, List<Contribution> breakdow
             contributions.add(new Contribution("bright_lighting", -1, BRIGHT_LIGHTING_COST,
                     "Seeded bright lighting"));
         }
-        AgeSkyProfile sky = plan == null && ageSeed != Long.MIN_VALUE ? AgeSkyProfile.random(ageSeed, traits)
+        AgeSkyProfile sky = plan == null && ageSeed != Long.MIN_VALUE ? AgeSkyProfile.random(ageSeed, traits, policy)
                 : plan == null ? new AgeSkyProfile(AgeSkyProfile.Style.INHERITED, -1, List.of())
                 : AgeSkyProfile.compile(plan, traits);
         int seenSuns = 0;
diff --git a/src/main/java/net/dnorberg/rivencraft/book/AgeRegistrySavedData.java b/src/main/java/net/dnorberg/rivencraft/book/AgeRegistrySavedData.java
index 1c99910..310f16a 100644
--- a/src/main/java/net/dnorberg/rivencraft/book/AgeRegistrySavedData.java
+++ b/src/main/java/net/dnorberg/rivencraft/book/AgeRegistrySavedData.java
@@ -39,6 +39,7 @@ public final class AgeRegistrySavedData extends SavedData {
     private static final String TRAITS_TAG = "Traits";
     private static final String PLAN_TAG = "GenerationPlan";
     private static final String RANDOM_FEATURES_TAG = "RandomFeatures";
+    private static final String RANDOM_PAGE_POLICY_TAG = "RandomPagePolicy";
     private static final String SEASON_MODE_TAG = "SeasonMode";
     private static final String INSTABILITY_TAG = "Instability";
     private static final String INSTABILITY_PLAN_TAG = "InstabilityPlan";
@@ -77,9 +78,19 @@ public final class AgeRegistrySavedData extends SavedData {
         ServerLevel overworld = level.getServer().overworld();
         AgeRegistrySavedData data = get(overworld);
         long seed = ageSeed(overworld.getSeed(), data.availableDimensionId(normalizedName(name)));
-        AgeGenerationPlan.compile(writing, seed,
+        AgeGenerationPlan plan = AgeGenerationPlan.compile(writing, seed,
                 AgeRuntimeProfiles.selectForWriting(seed, writing, overworld.registryAccess()), AgeTraits.select(seed),
                 overworld.registryAccess());
+        if (plan == null) {
+            RandomPagePolicy policy = RandomPagePolicy.configured();
+            ResourceLocation profileId = AgeRuntimeProfiles.select(seed, policy);
+            AgeRuntimeProfile profile = AgeRuntimeProfiles.resolve(profileId);
+            AgeTraits traits = AgeTraits.select(seed, policy);
+            AgeBiomeSelection.compile(net.dnorberg.rivencraft.writing.WritingGrammar.parse(OrderedWriting.EMPTY),
+                    traits, profile, seed, overworld.registryAccess(), policy);
+            AgeSkyProfile.random(seed, traits, policy);
+            AgeSeasonMode.select(null, seed, ModList.get().isLoaded("sereneseasons"), profile, policy);
+        }
     }
 
     public static ResourceLocation previewGenerationProfile(ServerLevel level, String name) {
@@ -155,7 +166,8 @@ public final class AgeRegistrySavedData extends SavedData {
         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());
+                previous.randomFeatures(), previous.instability(), previous.instabilityPlan(),
+                previous.randomPagePolicy());
         if (AgeDimensionService.unload(server, previous) == AgeDimensionService.UnloadResult.FAILED)
             return false;
         ages.put(ageId, changed);
@@ -173,13 +185,19 @@ public final class AgeRegistrySavedData extends SavedData {
         String name = normalizedName(reference.name());
         ResourceLocation dimensionId = availableDimensionId(name);
         long seed = ageSeed(worldSeed, dimensionId);
+        RandomPagePolicy policy = RandomPagePolicy.configured();
         ResourceLocation seedProfile = AgeRuntimeProfiles.selectForWriting(seed, writing, registries);
         AgeTraits traits = AgeTraits.select(seed);
         AgeGenerationPlan plan = AgeGenerationPlan.compile(writing, seed, seedProfile, traits, registries);
+        if (plan == null) {
+            seedProfile = AgeRuntimeProfiles.select(seed, policy);
+            traits = AgeTraits.select(seed, policy);
+        }
         AgeTraits effectiveTraits = plan == null
                 ? AgeEnvironmentCompiler.forTerrain(traits, AgeRuntimeProfiles.resolve(seedProfile))
                 : AgeEnvironmentCompiler.apply(plan, traits);
-        AgeInstability instability = AgeInstability.compute(plan, effectiveTraits, registries, seed);
+        AgeInstability instability = AgeInstability.compute(plan, effectiveTraits, registries, seed,
+                plan == null ? policy : RandomPagePolicy.UNRESTRICTED);
         AgeInstabilityPlan instabilityPlan = AgeInstabilityPlan.select(instability, seed);
         AgeDefinition created = new AgeDefinition(
                 reference.id(),
@@ -193,11 +211,13 @@ public final class AgeRegistrySavedData extends SavedData {
                 effectiveTraits,
                 plan,
                 AgeSeasonMode.select(plan, seed, ModList.get().isLoaded("sereneseasons"),
-                        plan == null ? AgeRuntimeProfiles.resolve(seedProfile) : plan.runtimeProfile()),
+                        plan == null ? AgeRuntimeProfiles.resolve(seedProfile) : plan.runtimeProfile(),
+                        plan == null ? policy : RandomPagePolicy.UNRESTRICTED),
                 plan == null ? AgeFeatureSelection.randomChoices(seed,
-                        AgeRuntimeProfiles.resolve(seedProfile), registries) : List.of(),
+                        AgeRuntimeProfiles.resolve(seedProfile), registries, policy) : List.of(),
                 instability,
-                instabilityPlan
+                instabilityPlan,
+                plan == null ? policy : RandomPagePolicy.UNRESTRICTED
         );
         ages.put(created.id(), created);
         setDirty();
@@ -264,7 +284,10 @@ public final class AgeRegistrySavedData extends SavedData {
                             ? AgeSeasonMode.parseOrNull(entry.getString(SEASON_MODE_TAG)) : null,
                     readRandomFeatures(entry),
                     instability,
-                    instabilityPlan
+                    instabilityPlan,
+                    entry.contains(RANDOM_PAGE_POLICY_TAG, CompoundTag.TAG_COMPOUND)
+                            ? RandomPagePolicy.load(entry.getCompound(RANDOM_PAGE_POLICY_TAG))
+                            : RandomPagePolicy.UNRESTRICTED
             ));
         }
         return data;
@@ -309,6 +332,7 @@ public final class AgeRegistrySavedData extends SavedData {
                         entry.put(RANDOM_FEATURES_TAG, featureTags);
                     }
                     if (age.seasonMode() != null) entry.putString(SEASON_MODE_TAG, age.seasonMode().name());
+                    if (age.plan() == null) entry.put(RANDOM_PAGE_POLICY_TAG, age.randomPagePolicy().save());
                     entry.put(INSTABILITY_TAG, age.instability().save());
                     entry.put(INSTABILITY_PLAN_TAG, age.instabilityPlan().save());
                     serializedAges.add(entry);
diff --git a/src/main/java/net/dnorberg/rivencraft/book/AgeRuntimeProfiles.java b/src/main/java/net/dnorberg/rivencraft/book/AgeRuntimeProfiles.java
index decf341..ac98875 100644
--- a/src/main/java/net/dnorberg/rivencraft/book/AgeRuntimeProfiles.java
+++ b/src/main/java/net/dnorberg/rivencraft/book/AgeRuntimeProfiles.java
@@ -57,20 +57,39 @@ public final class AgeRuntimeProfiles {
 
     /** Selects from all valid loaded profiles in stable resource-ID order. */
     public static ResourceLocation select(long seed) {
+        return select(seed, RandomPagePolicy.UNRESTRICTED);
+    }
+
+    public static ResourceLocation select(long seed, RandomPagePolicy policy) {
         if (PROFILES.isEmpty()) {
-            return AgeGenerationProfiles.select(seed);
+            List<LegacyRankChoice.Option<ResourceLocation>> profiles = policy.required(
+                    AgeGenerationProfiles.all().stream().sorted()
+                            .map(id -> new LegacyRankChoice.Option<>(id, AgeGenerationProfiles.randomRank(id)))
+                            .toList(), option -> terrainPage(option.value()),
+                    new LegacyRankChoice.Option<>(AgeGenerationProfiles.STANDARD, 1));
+            return LegacyRankChoice.choose(new Random(seed ^ 0x5445525241494E4CL), profiles);
         }
-        List<LegacyRankChoice.Option<ResourceLocation>> profiles = PROFILES.keySet().stream().sorted()
+        List<LegacyRankChoice.Option<ResourceLocation>> available = PROFILES.keySet().stream().sorted()
                 .map(id -> new LegacyRankChoice.Option<>(id, AgeGenerationProfiles.randomRank(id))).toList();
+        LegacyRankChoice.Option<ResourceLocation> fallback = available.stream()
+                .filter(option -> option.value().equals(AgeGenerationProfiles.STANDARD))
+                .findFirst().orElse(available.getFirst());
+        List<LegacyRankChoice.Option<ResourceLocation>> profiles = policy.required(available,
+                option -> terrainPage(option.value()), fallback);
         return LegacyRankChoice.choose(new Random(seed ^ 0x5445525241494E4CL), profiles);
     }
 
+    private static ResourceLocation terrainPage(ResourceLocation profile) {
+        return ResourceLocation.fromNamespaceAndPath("rivencraft", "terrain/" + profile.getPath());
+    }
+
     /** Keep seed-selected terrain random, but only among profiles able to host authored features. */
     public static ResourceLocation selectForWriting(long seed, OrderedWriting writing, RegistryAccess registries) {
-        ResourceLocation selected = select(seed);
         WritingGrammar.Result parsed = WritingGrammar.parse(writing);
-        if (parsed.activeSymbols().stream().anyMatch(symbol ->
-                symbol.semantics().role() == SymbolSemantics.Role.TERRAIN)) return selected;
+        boolean authoredTerrain = parsed.activeSymbols().stream().anyMatch(symbol ->
+                symbol.semantics().role() == SymbolSemantics.Role.TERRAIN);
+        ResourceLocation selected = select(seed);
+        if (authoredTerrain) return selected;
         List<ResourceLocation> features = parsed.activeSymbols().stream()
                 .filter(symbol -> symbol.semantics().role() == SymbolSemantics.Role.FEATURE)
                 .map(symbol -> ((SymbolSemantics.ResourceValue) symbol.semantics().value()).id()).toList();
diff --git a/src/main/java/net/dnorberg/rivencraft/book/AgeSeasonMode.java b/src/main/java/net/dnorberg/rivencraft/book/AgeSeasonMode.java
index 5fee177..9e2683d 100644
--- a/src/main/java/net/dnorberg/rivencraft/book/AgeSeasonMode.java
+++ b/src/main/java/net/dnorberg/rivencraft/book/AgeSeasonMode.java
@@ -24,15 +24,23 @@ public enum AgeSeasonMode {
 
     public static AgeSeasonMode select(AgeGenerationPlan plan, long ageSeed, boolean sereneInstalled,
                                        AgeRuntimeProfile profile) {
+        return select(plan, ageSeed, sereneInstalled, profile, RandomPagePolicy.UNRESTRICTED);
+    }
+
+    public static AgeSeasonMode select(AgeGenerationPlan plan, long ageSeed, boolean sereneInstalled,
+                                       AgeRuntimeProfile profile, RandomPagePolicy policy) {
         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(
+        return sereneInstalled ? LegacyRankChoice.choose(new Random(ageSeed ^ RANDOM_SALT), policy.required(List.of(
                 new LegacyRankChoice.Option<>(SEASONS, 1),
                 new LegacyRankChoice.Option<>(NO_SEASONS, 2),
                 new LegacyRankChoice.Option<>(ETERNAL_WINTER, 3),
                 new LegacyRankChoice.Option<>(ETERNAL_SUMMER, 3),
                 new LegacyRankChoice.Option<>(ETERNAL_FALL, 3),
-                new LegacyRankChoice.Option<>(ETERNAL_SPRING, 3))) : null;
+                new LegacyRankChoice.Option<>(ETERNAL_SPRING, 3)),
+                option -> net.minecraft.resources.ResourceLocation.fromNamespaceAndPath("rivencraft",
+                        "season/" + option.value().name().toLowerCase(Locale.ROOT)),
+                new LegacyRankChoice.Option<>(NO_SEASONS, 2))) : null;
     }
 
     /** Existing Ages without a stored choice retain their old cycling behavior. */
diff --git a/src/main/java/net/dnorberg/rivencraft/book/AgeSkyProfile.java b/src/main/java/net/dnorberg/rivencraft/book/AgeSkyProfile.java
index a82132a..f5202ba 100644
--- a/src/main/java/net/dnorberg/rivencraft/book/AgeSkyProfile.java
+++ b/src/main/java/net/dnorberg/rivencraft/book/AgeSkyProfile.java
@@ -6,6 +6,7 @@ import java.util.List;
 import java.util.Random;
 import java.util.Set;
 import net.dnorberg.rivencraft.writing.SymbolSemantics;
+import net.minecraft.resources.ResourceLocation;
 
 /** The ordered, deterministic sky specification for an Age. No client data is trusted here. */
 public record AgeSkyProfile(Style style, int color, List<Body> bodies) {
@@ -23,16 +24,25 @@ public record AgeSkyProfile(Style style, int color, List<Body> bodies) {
     public static AgeSkyProfile forAge(AgeDefinition age) {
         if (age.plan() != null) return compile(age.plan(), age.traits());
         if (age.generationVersion() >= RANDOM_SKY_GENERATION_VERSION)
-            return random(age.seed(), age.traits());
+            return random(age.seed(), age.traits(), age.randomPagePolicy());
         return new AgeSkyProfile(Style.INHERITED, -1, List.of());
     }
 
     public static AgeSkyProfile random(long seed, AgeTraits traits) {
+        return random(seed, traits, RandomPagePolicy.UNRESTRICTED);
+    }
+
+    public static AgeSkyProfile random(long seed, AgeTraits traits, RandomPagePolicy policy) {
         Random random = new Random(seed ^ 0x534B5950524F464CL);
-        Style style = Style.values()[random.nextInt(Style.values().length)];
+        List<Style> styles = policy.required(java.util.Arrays.stream(Style.values())
+                .filter(style -> style != Style.INHERITED || !policy.restricts("sky")).toList(),
+                AgeSkyProfile::skyPage, Style.INHERITED);
+        Style style = styles.get(random.nextInt(styles.size()));
         int color = randomColor(random);
-        int suns = random.nextInt(4);
-        int moons = random.nextInt(4);
+        int suns = policy.allows(ResourceLocation.fromNamespaceAndPath("rivencraft", "celestial/sun"))
+                ? random.nextInt(4) : 0;
+        int moons = policy.allows(ResourceLocation.fromNamespaceAndPath("rivencraft", "celestial/moon"))
+                ? random.nextInt(4) : 0;
         List<Body> bodies = new ArrayList<>();
         for (int i = 0; i < suns; i++)
             bodies.add(new Body(Kind.SUN, randomColor(random),
@@ -45,6 +55,11 @@ public record AgeSkyProfile(Style style, int color, List<Body> bodies) {
         return new AgeSkyProfile(style, color, bodies);
     }
 
+    private static ResourceLocation skyPage(Style style) {
+        return ResourceLocation.fromNamespaceAndPath("rivencraft",
+                "sky/" + (style == Style.INHERITED ? "inherited" : style.name().toLowerCase(java.util.Locale.ROOT)));
+    }
+
     public static AgeSkyProfile compile(AgeGenerationPlan plan, AgeTraits traits) {
         if (plan == null) return new AgeSkyProfile(Style.INHERITED, -1, List.of());
         Style style = Style.INHERITED;
diff --git a/src/main/java/net/dnorberg/rivencraft/book/AgeStructureSelection.java b/src/main/java/net/dnorberg/rivencraft/book/AgeStructureSelection.java
index 738cdf8..8bb6d36 100644
--- a/src/main/java/net/dnorberg/rivencraft/book/AgeStructureSelection.java
+++ b/src/main/java/net/dnorberg/rivencraft/book/AgeStructureSelection.java
@@ -157,7 +157,14 @@ public final class AgeStructureSelection {
 
     public static List<AgeFeatureSelection.Choice> randomChoices(long ageSeed, AgeRuntimeProfile profile,
                                                                    AgeBiomeSelection biomes, RegistryAccess registries) {
+        return randomChoices(ageSeed, profile, biomes, registries, RandomPagePolicy.UNRESTRICTED);
+    }
+
+    public static List<AgeFeatureSelection.Choice> randomChoices(long ageSeed, AgeRuntimeProfile profile,
+                                                                   AgeBiomeSelection biomes, RegistryAccess registries,
+                                                                   RandomPagePolicy policy) {
         List<LegacyRankChoice.Option<ResourceLocation>> eligible = new ArrayList<>(FEATURES.stream()
+                .filter(id -> policy.allows(ResourceLocation.fromNamespaceAndPath("rivencraft", "feature/" + id.getPath())))
                 .filter(id -> error(id, profile, biomes, registries) == null)
                 .filter(id -> dungeons(id) || biomeCompatible(id, biomes, registries))
                 .map(id -> new LegacyRankChoice.Option<>(id, randomRank(id))).toList());
diff --git a/src/main/java/net/dnorberg/rivencraft/book/AgeTraits.java b/src/main/java/net/dnorberg/rivencraft/book/AgeTraits.java
index 503b45a..70f5fb3 100644
--- a/src/main/java/net/dnorberg/rivencraft/book/AgeTraits.java
+++ b/src/main/java/net/dnorberg/rivencraft/book/AgeTraits.java
@@ -2,6 +2,8 @@ package net.dnorberg.rivencraft.book;
 
 import java.util.Random;
 import java.util.List;
+import java.util.Locale;
+import net.minecraft.resources.ResourceLocation;
 
 /** Immutable random-Age traits selected once from the Age seed. */
 public record AgeTraits(
@@ -42,8 +44,12 @@ public record AgeTraits(
     }
 
     public static AgeTraits select(long seed) {
+        return select(seed, RandomPagePolicy.UNRESTRICTED);
+    }
+
+    public static AgeTraits select(long seed, RandomPagePolicy policy) {
         Random random = new Random(seed ^ 0x524956454E435241L);
-        BiomeDistribution biomeDistribution = LegacyRankChoice.choose(random, List.of(
+        BiomeDistribution biomeDistribution = LegacyRankChoice.choose(random, policy.required(List.of(
                 new LegacyRankChoice.Option<>(BiomeDistribution.NATIVE, 1),
                 new LegacyRankChoice.Option<>(BiomeDistribution.SINGLE, 1),
                 new LegacyRankChoice.Option<>(BiomeDistribution.MEDIUM, 1),
@@ -52,12 +58,16 @@ public record AgeTraits(
                 new LegacyRankChoice.Option<>(BiomeDistribution.TINY, 2),
                 new LegacyRankChoice.Option<>(BiomeDistribution.SMALL, 2),
                 new LegacyRankChoice.Option<>(BiomeDistribution.LARGE, 2),
-                new LegacyRankChoice.Option<>(BiomeDistribution.HUGE, 2)));
-        Lighting lighting = LegacyRankChoice.choose(random, List.of(
+                new LegacyRankChoice.Option<>(BiomeDistribution.HUGE, 2)),
+                option -> page("biome", option.value()),
+                new LegacyRankChoice.Option<>(BiomeDistribution.NATIVE, 1)));
+        Lighting lighting = LegacyRankChoice.choose(random, policy.required(List.of(
                 new LegacyRankChoice.Option<>(Lighting.NORMAL, 1),
                 new LegacyRankChoice.Option<>(Lighting.DARK, 2),
-                new LegacyRankChoice.Option<>(Lighting.BRIGHT, 2)));
-        Weather weather = LegacyRankChoice.choose(random, List.of(
+                new LegacyRankChoice.Option<>(Lighting.BRIGHT, 2)),
+                option -> page("lighting", option.value()),
+                new LegacyRankChoice.Option<>(Lighting.NORMAL, 1)));
+        Weather weather = LegacyRankChoice.choose(random, policy.required(List.of(
                 new LegacyRankChoice.Option<>(Weather.NORMAL, 1),
                 new LegacyRankChoice.Option<>(Weather.FAST, 2),
                 new LegacyRankChoice.Option<>(Weather.SLOW, 2),
@@ -66,7 +76,9 @@ public record AgeTraits(
                 new LegacyRankChoice.Option<>(Weather.CLOUDY, 2),
                 new LegacyRankChoice.Option<>(Weather.RAIN, 2),
                 new LegacyRankChoice.Option<>(Weather.SNOW, 2),
-                new LegacyRankChoice.Option<>(Weather.STORM, 2)));
+                new LegacyRankChoice.Option<>(Weather.STORM, 2)),
+                option -> page("weather", option.value()),
+                new LegacyRankChoice.Option<>(Weather.NORMAL, 1)));
         // Legacy's PERIOD_BASIC grammar gives ModZero rank 2 and its other
         // three length modifiers rank 1, producing an effective 1-in-7 weight.
         boolean stopped = random.nextInt(7) == 0;
@@ -81,6 +93,11 @@ public record AgeTraits(
         );
     }
 
+    private static ResourceLocation page(String category, Enum<?> value) {
+        return ResourceLocation.fromNamespaceAndPath("rivencraft",
+                category + "/" + value.name().toLowerCase(Locale.ROOT));
+    }
+
     public boolean hasStoppedCelestialCycle() {
         return celestialPeriod == STOPPED_CELESTIAL_PERIOD;
     }
diff --git a/src/main/java/net/dnorberg/rivencraft/book/RandomPagePolicy.java b/src/main/java/net/dnorberg/rivencraft/book/RandomPagePolicy.java
new file mode 100644
index 0000000..a137d2c
--- /dev/null
+++ b/src/main/java/net/dnorberg/rivencraft/book/RandomPagePolicy.java
@@ -0,0 +1,91 @@
+package net.dnorberg.rivencraft.book;
+
+import java.util.List;
+import java.util.Set;
+import java.util.stream.Collectors;
+import net.dnorberg.rivencraft.config.RivencraftConfig;
+import net.minecraft.nbt.CompoundTag;
+import net.minecraft.nbt.ListTag;
+import net.minecraft.nbt.StringTag;
+import net.minecraft.resources.ResourceLocation;
+
+/** A snapshot of Page eligibility, frozen with each random Age at binding time. */
+public record RandomPagePolicy(Set<ResourceLocation> allowlist, Set<ResourceLocation> blocklist) {
+    public static final RandomPagePolicy UNRESTRICTED = new RandomPagePolicy(Set.of(), Set.of());
+
+    public RandomPagePolicy {
+        allowlist = Set.copyOf(allowlist);
+        blocklist = Set.copyOf(blocklist);
+    }
+
+    public static RandomPagePolicy configured() {
+        return new RandomPagePolicy(parse(RivencraftConfig.randomPageAllowlist()),
+                parse(RivencraftConfig.randomPageBlocklist()));
+    }
+
+    private static Set<ResourceLocation> parse(List<? extends String> ids) {
+        return ids.stream().map(RandomPagePolicy::parsePageId).collect(Collectors.toUnmodifiableSet());
+    }
+
+    /** Server config IDs may omit the built-in Rivencraft namespace. */
+    public static ResourceLocation parsePageId(String value) {
+        ResourceLocation id = ResourceLocation.tryParse(value.contains(":") ? value : "rivencraft:" + value);
+        if (id == null) throw new IllegalArgumentException("Invalid Page ID " + value);
+        return id;
+    }
+
+    public boolean allows(ResourceLocation id) {
+        if (blocklist.contains(id)) return false;
+        String category = category(id);
+        return !restricts(category) || allowlist.contains(id);
+    }
+
+    public boolean restricts(String category) {
+        return allowlist.stream().anyMatch(entry -> category(entry).equals(category));
+    }
+
+    public <T> List<T> eligible(List<T> candidates, java.util.function.Function<T, ResourceLocation> pageId) {
+        return candidates.stream().filter(candidate -> allows(pageId.apply(candidate))).toList();
+    }
+
+    public <T> List<T> required(List<T> candidates, java.util.function.Function<T, ResourceLocation> pageId,
+                                T fallback) {
+        List<T> eligible = eligible(candidates, pageId);
+        return eligible.isEmpty() ? List.of(fallback) : eligible;
+    }
+
+    private static String category(ResourceLocation id) {
+        String path = id.getPath();
+        if (path.startsWith("biome/") && java.util.Set.of("native", "single", "tiled", "grid",
+                "tiny", "small", "medium", "large", "huge").contains(path.substring("biome/".length())))
+            return "biome_distribution";
+        return path.substring(0, path.indexOf('/') < 0 ? path.length() : path.indexOf('/'));
+    }
+
+    public CompoundTag save() {
+        CompoundTag tag = new CompoundTag();
+        tag.put("Allowlist", strings(allowlist));
+        tag.put("Blocklist", strings(blocklist));
+        return tag;
+    }
+
+    public static RandomPagePolicy load(CompoundTag tag) {
+        return new RandomPagePolicy(read(tag.getList("Allowlist", StringTag.TAG_STRING)),
+                read(tag.getList("Blocklist", StringTag.TAG_STRING)));
+    }
+
+    private static ListTag strings(Set<ResourceLocation> ids) {
+        ListTag tags = new ListTag();
+        ids.stream().sorted().forEach(id -> tags.add(StringTag.valueOf(id.toString())));
+        return tags;
+    }
+
+    private static Set<ResourceLocation> read(ListTag tags) {
+        java.util.Set<ResourceLocation> ids = new java.util.HashSet<>();
+        for (int index = 0; index < tags.size(); index++) {
+            ResourceLocation id = ResourceLocation.tryParse(tags.getString(index));
+            if (id != null) ids.add(id);
+        }
+        return Set.copyOf(ids);
+    }
+}
diff --git a/src/main/java/net/dnorberg/rivencraft/config/RivencraftConfig.java b/src/main/java/net/dnorberg/rivencraft/config/RivencraftConfig.java
index bd643b1..6268d81 100644
--- a/src/main/java/net/dnorberg/rivencraft/config/RivencraftConfig.java
+++ b/src/main/java/net/dnorberg/rivencraft/config/RivencraftConfig.java
@@ -23,6 +23,8 @@ public final class RivencraftConfig {
     private static final ModConfigSpec.EnumValue<LibraryLootMode> LIBRARY_LOOT_MODE;
     private static final ModConfigSpec.IntValue SYMBOL_INK_COST;
     private static final ModConfigSpec.IntValue LINK_PANEL_INK_COST;
+    private static final ModConfigSpec.ConfigValue<List<? extends String>> RANDOM_PAGE_ALLOWLIST;
+    private static final ModConfigSpec.ConfigValue<List<? extends String>> RANDOM_PAGE_BLOCKLIST;
     private static final ModConfigSpec.BooleanValue AUTO_WHITELIST_SERENE_AGES;
     private static final ModConfigSpec.BooleanValue INSTABILITY_ENABLED;
     private static final ModConfigSpec.IntValue INSTABILITY_DIFFICULTY;
@@ -89,6 +91,21 @@ public final class RivencraftConfig {
         LINK_PANEL_INK_COST = builder.comment("Ink units consumed when preparing one baseline link-panel page.")
                 .defineInRange("link_panel_ink_cost", 2, 1, 16);
         builder.pop();
+        builder.push("random_pages");
+        RANDOM_PAGE_ALLOWLIST = builder.comment(
+                "Optional Page paths allowed in new random Ages and newly generated library loot.",
+                "The allowlist restricts only categories it mentions; unmentioned categories remain unrestricted.",
+                "Example: [\"sky/static\"] restricts random sky styles to Static Sky.",
+                "Full namespaced IDs are also accepted for compatibility.")
+                .defineList("allowlist", List.<String>of(), () -> "sky/static",
+                        RivencraftConfig::validPageId);
+        RANDOM_PAGE_BLOCKLIST = builder.comment(
+                "Page paths excluded from new random Ages and newly generated library loot.",
+                "The blocklist wins over the allowlist. Example: [\"sky/static\"].",
+                "Existing Ages and Pages deliberately remain usable in hand-authored books.")
+                .defineList("blocklist", List.<String>of(), () -> "sky/static",
+                        RivencraftConfig::validPageId);
+        builder.pop();
         builder.push("serene_seasons");
         AUTO_WHITELIST_SERENE_AGES = builder.comment(
                 "Automatically add Rivencraft Ages to Serene Seasons' dimension whitelist when loaded.",
@@ -233,6 +250,14 @@ public final class RivencraftConfig {
         return LINK_PANEL_INK_COST.get();
     }
 
+    public static List<? extends String> randomPageAllowlist() { return RANDOM_PAGE_ALLOWLIST.get(); }
+    public static List<? extends String> randomPageBlocklist() { return RANDOM_PAGE_BLOCKLIST.get(); }
+
+    private static boolean validPageId(Object value) {
+        return value instanceof String id && !id.isBlank()
+                && ResourceLocation.tryParse(id.contains(":") ? id : "rivencraft:" + id) != null;
+    }
+
     public static boolean autoWhitelistSereneAges() {
         return AUTO_WHITELIST_SERENE_AGES.get();
     }
diff --git a/src/main/java/net/dnorberg/rivencraft/gametest/LinkingGameTests.java b/src/main/java/net/dnorberg/rivencraft/gametest/LinkingGameTests.java
index 7d92e1a..e34595f 100644
--- a/src/main/java/net/dnorberg/rivencraft/gametest/LinkingGameTests.java
+++ b/src/main/java/net/dnorberg/rivencraft/gametest/LinkingGameTests.java
@@ -212,8 +212,10 @@ public final class LinkingGameTests {
                 "A page-free book must select a supported legacy-inspired terrain profile");
         helper.assertValueEqual(first.generationVersion(), AgeDefinition.CURRENT_GENERATION_VERSION,
                 "New Ages must record the current generation algorithm version");
-        helper.assertValueEqual(first.traits(), AgeTraits.select(first.seed()),
-                "A page-free book must persist the deterministic traits selected from its seed");
+        helper.assertValueEqual(first.traits(), net.dnorberg.rivencraft.book.AgeEnvironmentCompiler.forTerrain(
+                        AgeTraits.select(first.seed()),
+                        net.dnorberg.rivencraft.book.AgeRuntimeProfiles.resolve(first.generationProfile())),
+                "A page-free book must persist deterministic traits, with Cave sky/weather normalization");
         helper.assertTrue(first.traits().hasStoppedCelestialCycle()
                         || first.traits().celestialPeriod() >= AgeTraits.MIN_CELESTIAL_PERIOD
                         && first.traits().celestialPeriod() <= AgeTraits.MAX_CELESTIAL_PERIOD,
diff --git a/src/main/java/net/dnorberg/rivencraft/world/MystcraftLibraryFeature.java b/src/main/java/net/dnorberg/rivencraft/world/MystcraftLibraryFeature.java
index 3363684..06481d3 100644
--- a/src/main/java/net/dnorberg/rivencraft/world/MystcraftLibraryFeature.java
+++ b/src/main/java/net/dnorberg/rivencraft/world/MystcraftLibraryFeature.java
@@ -4,6 +4,7 @@ import java.util.List;
 import java.util.Optional;
 import java.util.concurrent.ConcurrentHashMap;
 import net.dnorberg.rivencraft.config.RivencraftConfig;
+import net.dnorberg.rivencraft.book.RandomPagePolicy;
 import net.dnorberg.rivencraft.block.BookStandBlock;
 import net.dnorberg.rivencraft.block.entity.BookStandBlockEntity;
 import net.dnorberg.rivencraft.item.PageItem;
@@ -336,9 +337,17 @@ public final class MystcraftLibraryFeature {
 
     static List<ResourceLocation> symbolsForLoot(List<ResourceLocation> ageSymbols,
                                                  RivencraftConfig.LibraryLootMode mode) {
+        return symbolsForLoot(ageSymbols, mode, RandomPagePolicy.configured());
+    }
+
+    static List<ResourceLocation> symbolsForLoot(List<ResourceLocation> ageSymbols,
+                                                 RivencraftConfig.LibraryLootMode mode,
+                                                 RandomPagePolicy policy) {
         return mode == RivencraftConfig.LibraryLootMode.AGE_ONLY ? ageSymbols.stream()
+                .filter(policy::allows)
                 .filter(id -> SymbolCatalog.isKnown(new SymbolReference(id))).distinct().toList()
                 : SymbolCatalog.symbols().entrySet().stream()
+                .filter(entry -> policy.allows(entry.getKey()))
                 .filter(entry -> entry.getKey().getNamespace().equals("rivencraft")
                         && entry.getValue().semantics().isPresent()
                         && !entry.getKey().getPath().startsWith("block/")
diff --git a/src/main/java/net/dnorberg/rivencraft/world/MystcraftLibraryGameTests.java b/src/main/java/net/dnorberg/rivencraft/world/MystcraftLibraryGameTests.java
index dd25455..f06e2fa 100644
--- a/src/main/java/net/dnorberg/rivencraft/world/MystcraftLibraryGameTests.java
+++ b/src/main/java/net/dnorberg/rivencraft/world/MystcraftLibraryGameTests.java
@@ -2,6 +2,7 @@ package net.dnorberg.rivencraft.world;
 
 import java.util.List;
 import net.dnorberg.rivencraft.config.RivencraftConfig;
+import net.dnorberg.rivencraft.book.RandomPagePolicy;
 import net.dnorberg.rivencraft.block.BookStandBlock;
 import net.dnorberg.rivencraft.block.entity.BookStandBlockEntity;
 import net.dnorberg.rivencraft.item.PageItem;
@@ -107,6 +108,85 @@ public final class MystcraftLibraryGameTests {
         helper.succeed();
     }
 
+    @GameTest(template = "empty")
+    public static void pageListsFilterRandomChoicesAndLibraryLoot(GameTestHelper helper) {
+        ResourceLocation staticSky = ResourceLocation.parse("rivencraft:sky/static");
+        ResourceLocation netherSky = ResourceLocation.parse("rivencraft:sky/nether");
+        ResourceLocation rocks = ResourceLocation.parse("rivencraft:feature/rocks");
+        helper.assertValueEqual(RandomPagePolicy.parsePageId("sky/static"), staticSky,
+                "A shorthand Page path must resolve to Rivencraft's namespace");
+        helper.assertValueEqual(RandomPagePolicy.parsePageId("rivencraft:sky/static"), staticSky,
+                "An existing fully qualified Page ID must still work");
+        RandomPagePolicy policy = new RandomPagePolicy(java.util.Set.of(staticSky, netherSky),
+                java.util.Set.of(netherSky, rocks));
+        helper.assertTrue(policy.allows(staticSky), "Allowlisted sky Page must remain available");
+        helper.assertTrue(!policy.allows(netherSky), "Blocklist must override allowlist");
+        helper.assertTrue(!policy.allows(rocks), "Blocked feature Page must be excluded");
+        helper.assertTrue(policy.allows(ResourceLocation.parse("rivencraft:terrain/standard")),
+                "Unmentioned categories must remain unrestricted");
+        RandomPagePolicy biomeController = new RandomPagePolicy(
+                java.util.Set.of(ResourceLocation.parse("rivencraft:biome/tiny")), java.util.Set.of());
+        helper.assertTrue(biomeController.allows(ResourceLocation.parse("rivencraft:biome/plains")),
+                "A biome-controller allowlist must not exclude actual biome Pages");
+        helper.assertTrue(!biomeController.allows(ResourceLocation.parse("rivencraft:biome/huge")),
+                "A biome-controller allowlist must constrain other distributions");
+        helper.assertValueEqual(RandomPagePolicy.load(policy.save()), policy,
+                "Random Age Page policy must survive save and reload");
+        helper.assertValueEqual(MystcraftLibraryFeature.symbolsForLoot(
+                        List.of(staticSky, netherSky, rocks), RivencraftConfig.LibraryLootMode.AGE_ONLY, policy),
+                List.of(staticSky), "Age-only library loot must exclude blocked Pages");
+        for (long seed = 0; seed < 100; seed++) {
+            helper.assertValueEqual(net.dnorberg.rivencraft.book.AgeSkyProfile.random(seed,
+                            net.dnorberg.rivencraft.book.AgeTraits.select(seed), policy).style(),
+                    net.dnorberg.rivencraft.book.AgeSkyProfile.Style.STATIC,
+                    "Sky allowlist must constrain new random Ages");
+        }
+        RandomPagePolicy singleTerrain = new RandomPagePolicy(
+                java.util.Set.of(ResourceLocation.parse("rivencraft:terrain/standard"),
+                        ResourceLocation.parse("rivencraft:lighting/normal")), java.util.Set.of());
+        for (long seed = 0; seed < 100; seed++) {
+            helper.assertValueEqual(net.dnorberg.rivencraft.book.AgeRuntimeProfiles.select(seed, singleTerrain),
+                    ResourceLocation.parse("rivencraft:standard"),
+                    "Random terrain must honor a category allowlist");
+            helper.assertValueEqual(net.dnorberg.rivencraft.book.AgeTraits.select(seed, singleTerrain).lighting(),
+                    net.dnorberg.rivencraft.book.AgeTraits.Lighting.NORMAL,
+                    "Random lighting must honor a category allowlist");
+        }
+        RandomPagePolicy noRequiredPages = new RandomPagePolicy(java.util.Set.of(
+                ResourceLocation.parse("rivencraft:terrain/not_present"),
+                ResourceLocation.parse("rivencraft:lighting/not_present"),
+                ResourceLocation.parse("rivencraft:weather/not_present"),
+                ResourceLocation.parse("rivencraft:sky/not_present"),
+                ResourceLocation.parse("rivencraft:season/not_present")), java.util.Set.of());
+        helper.assertValueEqual(net.dnorberg.rivencraft.book.AgeRuntimeProfiles.select(42L, noRequiredPages),
+                ResourceLocation.parse("rivencraft:standard"), "Empty terrain family must use Standard");
+        var fallbackTraits = net.dnorberg.rivencraft.book.AgeTraits.select(42L, noRequiredPages);
+        helper.assertValueEqual(fallbackTraits.lighting(),
+                net.dnorberg.rivencraft.book.AgeTraits.Lighting.NORMAL,
+                "Empty lighting family must use Normal");
+        helper.assertValueEqual(fallbackTraits.weather(),
+                net.dnorberg.rivencraft.book.AgeTraits.Weather.NORMAL,
+                "Empty weather family must use Normal");
+        helper.assertValueEqual(net.dnorberg.rivencraft.book.AgeSkyProfile.random(42L,
+                        fallbackTraits, noRequiredPages).style(),
+                net.dnorberg.rivencraft.book.AgeSkyProfile.Style.INHERITED,
+                "Empty sky family must use inherited sky");
+        helper.assertValueEqual(net.dnorberg.rivencraft.book.AgeSeasonMode.select(null, 42L,
+                        true, null, noRequiredPages),
+                net.dnorberg.rivencraft.book.AgeSeasonMode.NO_SEASONS,
+                "Empty season family must use No Seasons");
+        var blockedControllers = java.util.Arrays.stream(
+                        net.dnorberg.rivencraft.book.AgeTraits.BiomeDistribution.values())
+                .map(value -> ResourceLocation.parse("rivencraft:biome/"
+                        + value.name().toLowerCase(java.util.Locale.ROOT)))
+                .collect(java.util.stream.Collectors.toUnmodifiableSet());
+        helper.assertValueEqual(net.dnorberg.rivencraft.book.AgeTraits.select(42L,
+                        new RandomPagePolicy(java.util.Set.of(), blockedControllers)).biomeDistribution(),
+                net.dnorberg.rivencraft.book.AgeTraits.BiomeDistribution.NATIVE,
+                "Empty biome-distribution family must use Native");
+        helper.succeed();
+    }
+
     @GameTest(template = "empty")
     public static void testSpacingIsSessionOnlyAndKeepsLegacySites(GameTestHelper helper) {
         long seed = 881L;