diff --git a/src/@types/turn-move.ts b/src/@types/turn-move.ts
index f26e3b9e640..a5a69eb3749 100644
--- a/src/@types/turn-move.ts
+++ b/src/@types/turn-move.ts
@@ -10,4 +10,4 @@ export interface TurnMove {
   useMode: MoveUseMode;
   result?: MoveResult;
   turn?: number;
-}
\ No newline at end of file
+}
diff --git a/src/system/schema-migrators/custom-pokemon-data.ts b/src/system/schema-migrators/custom-pokemon-data.ts
index b979e3d1b8e..fc009d3c34b 100644
--- a/src/system/schema-migrators/custom-pokemon-data.ts
+++ b/src/system/schema-migrators/custom-pokemon-data.ts
@@ -1,5 +1,5 @@
-import type { Z$PokemonData } from "#system/schemas/v1.10/pokemon-data";
-import { NatureSchema } from "#system/schemas/v1.10/pokemon-nature";
+import type { Z$PokemonData } from "#system/schemas/pokemon/pokemon-data";
+import { NatureSchema } from "#system/schemas/pokemon/pokemon-nature";
 import type z from "zod";
 
 /**
diff --git a/src/system/schema-migrators/summon-data.ts b/src/system/schema-migrators/summon-data.ts
index 6268185a8a3..d836619fcec 100644
--- a/src/system/schema-migrators/summon-data.ts
+++ b/src/system/schema-migrators/summon-data.ts
@@ -1,5 +1,6 @@
 import { Z$PositiveInt } from "#system/schemas/common";
-import type { Z$IllusionData } from "#system/schemas/v1.10/illusion-data";
+import type { Z$IllusionData } from "#system/schemas/pokemon/illusion-data";
+import { isNullOrUndefined } from "#utils/common";
 import { getPokemonSpecies } from "#utils/pokemon-utils";
 import { z } from "zod";
 
@@ -29,6 +30,7 @@ import { z } from "zod";
  * ```
  *
  * As this version of the data is compatible with version 1.10, we only need to specify the new properties.
+ * In addition, the value type of `fusionSpecies` changed from `PokemonSpecies` to simply the species ID.
  */
 export const Z$V1_9_IllusionData = z.looseObject({
   species: Z$PositiveInt,
@@ -45,25 +47,27 @@ type V1_9_IllusionData = z.input<typeof Z$V1_9_IllusionData>;
  * Migrate illusion data from version 1.9 to 1.10
  *
  * @remarks
- * Extract `speciesId` from `fusionSpecies`, and use defaults for all fields from the illusioned pokemon.
+ * Extracts `speciesId` from `fusionSpecies`, and use defaults for all fields from the illusioned pokemon.
  *
+ * In version 1.9, the illusion's name and shiny state were not serialized.
+ * The name is recoverable from the species ID, but shiny state is not recoverable.
  */
 export function V1_10_IllusionDataMigrator(arg: V1_9_IllusionData): Partial<z.input<typeof Z$IllusionData>> {
   return Z$V1_9_IllusionData.transform(data => {
     // Needed to fetch a default name.
     const pokemon = getPokemonSpecies(data.species);
-    return {
+    const result = {
       ...(data as Omit<V1_9_IllusionData, "fusionSpecies">),
-      // unwrap fusion species
-      fusionSpecies: data.fusionSpecies?.speciesId,
-      // and use defaults for all fields from the illusioned pokemon
       name: pokemon.name,
-      nickname: pokemon.name,
       shiny: false,
-      fusionShiny: false,
-      variant: 0,
-      fusionVariant: 0,
-      fusionFormIndex: 0,
-    };
+    } as Partial<z.input<typeof Z$IllusionData>>;
+
+    // With no fusion species, these fields should be left undefined.
+    if (!isNullOrUndefined(data.fusionSpecies)) {
+      result.fusionSpecies = data.fusionSpecies.speciesId;
+      result.fusionShiny = false; // default shiny state
+      result.fusionVariant = 0; // default variant
+    }
+    return result;
   }).parse(arg);
 }
diff --git a/src/system/schemas/arena/arena-data.ts b/src/system/schemas/arena/arena-data.ts
new file mode 100644
index 00000000000..cd503ff04e2
--- /dev/null
+++ b/src/system/schemas/arena/arena-data.ts
@@ -0,0 +1,22 @@
+// biome-ignore-start lint/correctness/noUnusedImports: used in a tsdoc comment
+import type { SerializedArenaData } from "#system/arena-data";
+import { Z$Terrain } from "#system/schemas/arena/terrain";
+import { Z$Weather } from "#system/schemas/arena/weather";
+// biome-ignore-end lint/correctness/noUnusedImports: end
+import { Z$BiomeID } from "#system/schemas/biome-id";
+import { Z$NonNegativeInt } from "#system/schemas/common";
+import { z } from "zod";
+
+/**
+ * Zod schema for {@linkcode SerializedArenaData} as of version 1.10
+ */
+export const Z$ArenaData = z.object({
+  biome: Z$BiomeID,
+  weather: Z$Weather.optional().catch(undefined),
+  terrain: Z$Terrain.optional().catch(undefined),
+  tags: z
+    .array(0 as unknown as any)
+    .optional()
+    .catch(undefined),
+  playerTerasUsed: Z$NonNegativeInt.optional().catch(undefined),
+});
diff --git a/src/system/schemas/v1.10/session-save-data.ts b/src/system/schemas/arena/arena-tag.ts
similarity index 100%
rename from src/system/schemas/v1.10/session-save-data.ts
rename to src/system/schemas/arena/arena-tag.ts
diff --git a/src/system/schemas/arena/terrain.ts b/src/system/schemas/arena/terrain.ts
new file mode 100644
index 00000000000..8b574393934
--- /dev/null
+++ b/src/system/schemas/arena/terrain.ts
@@ -0,0 +1,24 @@
+// biome-ignore-start lint/correctness/noUnusedImports: used in a tsdoc commentD
+import type { SerializedTerrain, TerrainType } from "#data/terrain";
+// biome-ignore-end lint/correctness/noUnusedImports: end
+import { z } from "zod";
+
+/**
+ * Zod schema for {@linkcode TerrainType} as of version 1.10.
+ *
+ * @remarks
+ * - `0`: NONE,
+ * - `1`: MISTY,
+ * - `2`: ELECTRIC,
+ * - `3`: GRASSY,
+ * - `4`: PSYCHIC
+ */
+export const Z$TerrainType = z.literal([0, 1, 2, 3, 4]);
+
+/**
+ * Zod schema for {@linkcode SerializedTerrain} as of version 1.10.
+ */
+export const Z$Terrain = z.object({
+  terrainType: Z$TerrainType,
+  turnsLeft: z.int(),
+});
diff --git a/src/system/schemas/arena/weather.ts b/src/system/schemas/arena/weather.ts
new file mode 100644
index 00000000000..84eaeb1ba18
--- /dev/null
+++ b/src/system/schemas/arena/weather.ts
@@ -0,0 +1,30 @@
+// biome-ignore-start lint/correctness/noUnusedImports: used in a tsdoc comment
+import type { Weather } from "#data/weather";
+import type { WeatherType } from "#enums/weather-type";
+// biome-ignore-end lint/correctness/noUnusedImports: used in a tsdoc comment
+import { z } from "zod";
+
+/**
+ * Zod schema for {@linkcode WeatherType} as of version 1.10.
+ *
+ * @remarks
+ * - `0`: NONE,
+ * - `1`: SUNNY,
+ * - `2`: RAIN,
+ * - `3`: SANDSTORM,
+ * - `4`: HAIL,
+ * - `5`: SNOW,
+ * - `6`: FOG,
+ * - `7`: HEAVY_RAIN,
+ * - `8`: HARSH_SUN,
+ * - `9`: STRONG_WINDS
+ */
+export const Z$WeatherType = z.literal([0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
+
+/**
+ * Zod schema for {@linkcode SerializedWeather} as of version 1.10.
+ */
+export const Z$Weather = z.object({
+  type: Z$WeatherType,
+  turnsLeft: z.int(),
+});
diff --git a/src/system/schemas/v1.10/berry-type.ts b/src/system/schemas/berry-type.ts
similarity index 100%
rename from src/system/schemas/v1.10/berry-type.ts
rename to src/system/schemas/berry-type.ts
diff --git a/src/system/schemas/v1.10/biome-id.ts b/src/system/schemas/biome-id.ts
similarity index 100%
rename from src/system/schemas/v1.10/biome-id.ts
rename to src/system/schemas/biome-id.ts
diff --git a/src/system/schemas/v1.10/move-result.ts b/src/system/schemas/moves/move-result.ts
similarity index 100%
rename from src/system/schemas/v1.10/move-result.ts
rename to src/system/schemas/moves/move-result.ts
diff --git a/src/system/schemas/v1.10/pokemon-move.ts b/src/system/schemas/moves/pokemon-move.ts
similarity index 99%
rename from src/system/schemas/v1.10/pokemon-move.ts
rename to src/system/schemas/moves/pokemon-move.ts
index 9eabecfa152..817ef35f8c9 100644
--- a/src/system/schemas/v1.10/pokemon-move.ts
+++ b/src/system/schemas/moves/pokemon-move.ts
@@ -1,6 +1,5 @@
 import { z } from "zod";
 
-
 /**
  * Zod schema for a Pokémon move, as of version 1.10.
  */
@@ -14,4 +13,3 @@ export const Z$PokemonMove = z.object({
 // If necessary, we can define `transforms` which implicitly create an instance of the class.
 
 export type ParsedPokemonMove = z.output<typeof Z$PokemonMove>;
-
diff --git a/src/system/schemas/v1.10/turn-move.ts b/src/system/schemas/moves/turn-move.ts
similarity index 70%
rename from src/system/schemas/v1.10/turn-move.ts
rename to src/system/schemas/moves/turn-move.ts
index da64c695936..2f08f63fb75 100644
--- a/src/system/schemas/v1.10/turn-move.ts
+++ b/src/system/schemas/moves/turn-move.ts
@@ -4,7 +4,7 @@ import type { TurnMove } from "#types/turn-move";
 // biome-ignore-end lint/correctness/noUnusedImports: used in tsdoc comment
 
 import { Z$NonNegativeInt, Z$PositiveInt } from "#system/schemas/common";
-import { Z$BattlerIndex } from "#system/schemas/v1.10/battler-index";
+import { Z$BattlerIndex } from "#system/schemas/pokemon/battler-index";
 import { Z$MoveResult } from "#system/schemas/v1.10/move-result";
 import { z } from "zod";
 
@@ -17,9 +17,9 @@ export const Z$MoveUseMode = z.literal([1, 2, 3, 4, 5]);
  * Zod schema for `{@linkcode TurnMove} as of version 1.10.
  */
 export const Z$TurnMove = z.object({
-    move: Z$PositiveInt,
-    targets: z.array(Z$BattlerIndex),
-    useMode: Z$MoveUseMode,
-    result: Z$MoveResult.optional().catch(undefined),
-    turn: Z$NonNegativeInt.optional().catch(undefined)
+  move: Z$PositiveInt,
+  targets: z.array(Z$BattlerIndex),
+  useMode: Z$MoveUseMode,
+  result: Z$MoveResult.optional().catch(undefined),
+  turn: Z$NonNegativeInt.optional().catch(undefined),
 });
diff --git a/src/system/schemas/v1.10/pokeball-type.ts b/src/system/schemas/pokeball-type.ts
similarity index 100%
rename from src/system/schemas/v1.10/pokeball-type.ts
rename to src/system/schemas/pokeball-type.ts
diff --git a/src/system/schemas/v1.10/battler-index.ts b/src/system/schemas/pokemon/battler-index.ts
similarity index 100%
rename from src/system/schemas/v1.10/battler-index.ts
rename to src/system/schemas/pokemon/battler-index.ts
diff --git a/src/system/schemas/v1.10/battler-tag.ts b/src/system/schemas/pokemon/battler-tag.ts
similarity index 83%
rename from src/system/schemas/v1.10/battler-tag.ts
rename to src/system/schemas/pokemon/battler-tag.ts
index 915ba29e6e1..4a43f0038ee 100644
--- a/src/system/schemas/v1.10/battler-tag.ts
+++ b/src/system/schemas/pokemon/battler-tag.ts
@@ -1,5 +1,5 @@
 import { Z$NonNegativeInt, Z$PositiveInt } from "#system/schemas/common";
-import { Z$BattlerIndex } from "#system/schemas/v1.10/battler-index";
+import { Z$BattlerIndex } from "#system/schemas/pokemon/battler-index";
 import { z } from "zod";
 
 /*
@@ -126,17 +126,17 @@ const Z$BattlerTagLapseType = z.literal([0, 1, 2, 3, 4, 5, 6, 7, 8]);
 
 // DamagingTrapTag may have a `commonAnim` field, though it's always instantiated.
 const Z$BattlerTag = z.object({
-    tagType: Z$BattlerTagType,
-    lapseTypes: z.array(Z$BattlerTagLapseType),
-    turnCount: Z$PositiveInt,
-    // Source move can be `none` for tags not applied by move, so allow `0` here.
-    sourceMove: Z$NonNegativeInt,
-    sourceId: z.int().optional().catch(undefined),
-    isBatonPassable: z.boolean(),
+  tagType: Z$BattlerTagType,
+  lapseTypes: z.array(Z$BattlerTagLapseType),
+  turnCount: Z$PositiveInt,
+  // Source move can be `none` for tags not applied by move, so allow `0` here.
+  sourceMove: Z$NonNegativeInt,
+  sourceId: z.int().optional().catch(undefined),
+  isBatonPassable: z.boolean(),
 });
 
 export const Z$SeedTag = z.object({
-    ...Z$BattlerTag.shape,
-    seedType: z.literal("SEEDED"),
-    sourceIndex: Z$BattlerIndex,
-})
+  ...Z$BattlerTag.shape,
+  seedType: z.literal("SEEDED"),
+  sourceIndex: Z$BattlerIndex,
+});
diff --git a/src/system/schemas/v1.10/custom-pokemon-data.ts b/src/system/schemas/pokemon/custom-pokemon-data.ts
similarity index 92%
rename from src/system/schemas/v1.10/custom-pokemon-data.ts
rename to src/system/schemas/pokemon/custom-pokemon-data.ts
index 3fb65753c94..eb1143f6f80 100644
--- a/src/system/schemas/v1.10/custom-pokemon-data.ts
+++ b/src/system/schemas/pokemon/custom-pokemon-data.ts
@@ -1,5 +1,5 @@
 import { Z$OptionalNonNegativeIntCatchToUndef, Z$PositiveInt } from "#schemas/common";
-import { Z$PokemonType } from "#system/schemas/v1.10/pokemon-type";
+import { Z$PokemonType } from "#system/schemas/pokemon/pokemon-type";
 import { z } from "zod";
 
 /**
diff --git a/src/system/schemas/v1.10/illusion-data.ts b/src/system/schemas/pokemon/illusion-data.ts
similarity index 87%
rename from src/system/schemas/v1.10/illusion-data.ts
rename to src/system/schemas/pokemon/illusion-data.ts
index 073db626dd9..abb955d2e3f 100644
--- a/src/system/schemas/v1.10/illusion-data.ts
+++ b/src/system/schemas/pokemon/illusion-data.ts
@@ -1,15 +1,14 @@
 import { Z$NonNegativeInt, Z$PositiveInt } from "#system/schemas/common";
+import { Z$Gender } from "#system/schemas/pokemon/pokemon-gender";
 import { Z$PokeballType } from "#system/schemas/v1.10/pokeball-type";
-import { Z$Gender } from "#system/schemas/v1.10/pokemon-gender";
 import { z } from "zod";
 
-
 // TODO: Write migrator for illusion data's fusionSpecies field
 // that transforms incoming fusion species
 
 export const Z$IllusionData = z.object({
   name: z.string(),
-  nickname: z.string(),
+  nickname: z.string().optional().catch(undefined),
   shiny: z.boolean(),
   variant: z.literal([0, 1, 2]).catch(0),
   species: Z$PositiveInt,
diff --git a/src/system/schemas/v1.10/pokemon-battle-data.ts b/src/system/schemas/pokemon/pokemon-battle-data.ts
similarity index 100%
rename from src/system/schemas/v1.10/pokemon-battle-data.ts
rename to src/system/schemas/pokemon/pokemon-battle-data.ts
diff --git a/src/system/schemas/v1.10/pokemon-data.ts b/src/system/schemas/pokemon/pokemon-data.ts
similarity index 89%
rename from src/system/schemas/v1.10/pokemon-data.ts
rename to src/system/schemas/pokemon/pokemon-data.ts
index b9476711c13..697add7ca8d 100644
--- a/src/system/schemas/v1.10/pokemon-data.ts
+++ b/src/system/schemas/pokemon/pokemon-data.ts
@@ -1,13 +1,13 @@
 import { Z$BoolCatchToFalse, Z$NonNegativeInt, Z$PositiveInt } from "#schemas/common";
 import { Z$PokeballType } from "#schemas/pokeball-type";
-import { Z$PokemonMove } from "#schemas/pokemon-move";
-import { Z$PokemonBattleData } from "#system/schemas/v1.10/pokemon-battle-data";
-import { Z$Gender } from "#system/schemas/v1.10/pokemon-gender";
+import { NatureSchema } from "#schemas/pokemon/pokemon-nature";
+import { Z$IVSet, Z$StatSet } from "#schemas/pokemon/pokemon-stats";
+import { StatusSchema } from "#schemas/status-effect";
+import { Z$PokemonMove } from "#system/schemas/moves/pokemon-move";
+import { Z$PokemonBattleData } from "#system/schemas/pokemon/pokemon-battle-data";
+import { Z$Gender } from "#system/schemas/pokemon/pokemon-gender";
 import z from "zod";
-import { NatureSchema } from "./pokemon-nature";
-import { Z$IVSet, Z$StatSet } from "./pokemon-stats";
 import { Z$PokemonType } from "./pokemon-type";
-import { StatusSchema } from "./status-effect";
 
 /**
  *  Not meant to actually be used itself.
diff --git a/src/system/schemas/v1.10/pokemon-gender.ts b/src/system/schemas/pokemon/pokemon-gender.ts
similarity index 100%
rename from src/system/schemas/v1.10/pokemon-gender.ts
rename to src/system/schemas/pokemon/pokemon-gender.ts
diff --git a/src/system/schemas/v1.10/pokemon-nature.ts b/src/system/schemas/pokemon/pokemon-nature.ts
similarity index 100%
rename from src/system/schemas/v1.10/pokemon-nature.ts
rename to src/system/schemas/pokemon/pokemon-nature.ts
diff --git a/src/system/schemas/v1.10/pokemon-species-form.ts b/src/system/schemas/pokemon/pokemon-species-form.ts
similarity index 92%
rename from src/system/schemas/v1.10/pokemon-species-form.ts
rename to src/system/schemas/pokemon/pokemon-species-form.ts
index aed8bbea42e..40b84af9e21 100644
--- a/src/system/schemas/v1.10/pokemon-species-form.ts
+++ b/src/system/schemas/pokemon/pokemon-species-form.ts
@@ -1,5 +1,5 @@
 import { Z$NonNegativeInt, Z$PositiveInt, Z$PositiveNumber } from "#system/schemas/common";
-import { Z$PokemonType } from "#system/schemas/v1.10/pokemon-type";
+import { Z$PokemonType } from "#system/schemas/pokemon/pokemon-type";
 import { z } from "zod";
 
 export const Z$PokemonSpeciesForm = z.object({
diff --git a/src/system/schemas/v1.10/pokemon-stats.ts b/src/system/schemas/pokemon/pokemon-stats.ts
similarity index 100%
rename from src/system/schemas/v1.10/pokemon-stats.ts
rename to src/system/schemas/pokemon/pokemon-stats.ts
diff --git a/src/system/schemas/v1.10/pokemon-summon-data.ts b/src/system/schemas/pokemon/pokemon-summon-data.ts
similarity index 77%
rename from src/system/schemas/v1.10/pokemon-summon-data.ts
rename to src/system/schemas/pokemon/pokemon-summon-data.ts
index b03a93ae2a2..161d5cd3229 100644
--- a/src/system/schemas/v1.10/pokemon-summon-data.ts
+++ b/src/system/schemas/pokemon/pokemon-summon-data.ts
@@ -1,9 +1,9 @@
 import { Z$NonNegativeInt } from "#system/schemas/common";
-import { Z$Gender } from "#system/schemas/v1.10/pokemon-gender";
-import { Z$PokemonMove } from "#system/schemas/v1.10/pokemon-move";
-import { Z$StatSet } from "#system/schemas/v1.10/pokemon-stats";
-import { Z$PokemonType } from "#system/schemas/v1.10/pokemon-type";
-import { Z$TurnMove } from "#system/schemas/v1.10/turn-move";
+import { Z$PokemonMove } from "#system/schemas/moves/pokemon-move";
+import { Z$TurnMove } from "#system/schemas/moves/turn-move";
+import { Z$Gender } from "#system/schemas/pokemon/pokemon-gender";
+import { Z$StatSet } from "#system/schemas/pokemon/pokemon-stats";
+import { Z$PokemonType } from "#system/schemas/pokemon/pokemon-type";
 import { z } from "zod";
 
 export const Z$SerializedSpeciesForm = z.object({
@@ -17,7 +17,7 @@ export const Z$SerializedSpeciesForm = z.object({
  * @remarks
  * All fields other than `stats` are optional, and catch to `undefined` on parse error,
  * allowing {@linkcode PokemonSummonData} to fill in defaults.
- * 
+ *
  */
 export const Z$PokemonSummonData = z.object({
   statSages: z.array(z.int().min(-6).max(6).catch(0)).optional().catch(undefined),
@@ -32,5 +32,5 @@ export const Z$PokemonSummonData = z.object({
   moveset: z.array(Z$PokemonMove).optional().catch(undefined),
   types: z.array(Z$PokemonType).optional().catch(undefined),
   addedType: Z$PokemonType.optional().catch(undefined),
-  illusion
+  illusion,
 });
diff --git a/src/system/schemas/v1.10/pokemon-type.ts b/src/system/schemas/pokemon/pokemon-type.ts
similarity index 100%
rename from src/system/schemas/v1.10/pokemon-type.ts
rename to src/system/schemas/pokemon/pokemon-type.ts
diff --git a/src/system/schemas/session-save-data.ts b/src/system/schemas/session-save-data.ts
new file mode 100644
index 00000000000..e69de29bb2d
diff --git a/src/system/schemas/v1.10/status-effect.ts b/src/system/schemas/status-effect.ts
similarity index 100%
rename from src/system/schemas/v1.10/status-effect.ts
rename to src/system/schemas/status-effect.ts
diff --git a/tsconfig.json b/tsconfig.json
index 780f33598c8..9c943473884 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -48,7 +48,12 @@
         "./system/version-migration/*.ts",
         "./system/*.ts"
       ],
-      "#schemas/*": ["./system/schemas/*.ts", "./system/schemas/v1.10/*.ts"],
+      "#schemas/*": [
+        "./system/schemas/*.ts",
+        "./system/schemas/arena/*.ts",
+        "./system/schemas/moves/*.ts",
+        "./system/schemas/pokemon/*.ts"
+      ],
       "#trainers/*": ["./data/trainers/*.ts"],
       "#types/*": ["./@types/helpers/*.ts", "./@types/*.ts", "./typings/phaser/*.ts"],
       "#ui/*": ["./ui/battle-info/*.ts", "./ui/settings/*.ts", "./ui/*.ts"],