diff --git a/src/data/biomes.ts b/src/data/biomes.ts
index 61da0410d..9014a77e1 100644
--- a/src/data/biomes.ts
+++ b/src/data/biomes.ts
@@ -34,6 +34,15 @@ interface BiomeDepths {
   [key: integer]: [integer, integer]
 }
 
+interface BiomeConditions {
+  [key: integer]: (p: any) => boolean;
+}
+
+export const biomeConditions: BiomeConditions = {
+  [Biome.TOWN]: (p) => !!p.scene.getParty().find(p => p.species.speciesId === Species.MEWTWO),
+  [Biome.PLAINS]: () => {return false},
+}
+
 export const biomeLinks: BiomeLinks = {
   [Biome.TOWN]: Biome.PLAINS,
   [Biome.PLAINS]: [ Biome.GRASS, Biome.METROPOLIS, Biome.LAKE ],
@@ -82,7 +91,8 @@ export enum BiomePoolTier {
   BOSS,
   BOSS_RARE,
   BOSS_SUPER_RARE,
-  BOSS_ULTRA_RARE
+  BOSS_ULTRA_RARE,
+  BOSS_CONDITIONAL_ULTRA_RARE
 };
 
 export const uncatchableSpecies: Species[] = [];
@@ -157,7 +167,8 @@ export const biomePokemonPools: BiomePokemonPools = {
     [BiomePoolTier.BOSS]: { [TimeOfDay.DAWN]: [], [TimeOfDay.DAY]: [], [TimeOfDay.DUSK]: [], [TimeOfDay.NIGHT]: [], [TimeOfDay.ALL]: [] },
     [BiomePoolTier.BOSS_RARE]: { [TimeOfDay.DAWN]: [], [TimeOfDay.DAY]: [], [TimeOfDay.DUSK]: [], [TimeOfDay.NIGHT]: [], [TimeOfDay.ALL]: [] },
     [BiomePoolTier.BOSS_SUPER_RARE]: { [TimeOfDay.DAWN]: [], [TimeOfDay.DAY]: [], [TimeOfDay.DUSK]: [], [TimeOfDay.NIGHT]: [], [TimeOfDay.ALL]: [] },
-    [BiomePoolTier.BOSS_ULTRA_RARE]: { [TimeOfDay.DAWN]: [], [TimeOfDay.DAY]: [], [TimeOfDay.DUSK]: [], [TimeOfDay.NIGHT]: [], [TimeOfDay.ALL]: [] }
+    [BiomePoolTier.BOSS_ULTRA_RARE]: { [TimeOfDay.DAWN]: [], [TimeOfDay.DAY]: [], [TimeOfDay.DUSK]: [], [TimeOfDay.NIGHT]: [], [TimeOfDay.ALL]: [Species.ZEKROM] },
+    [BiomePoolTier.BOSS_CONDITIONAL_ULTRA_RARE]: { [TimeOfDay.DAWN]: [], [TimeOfDay.DAY]: [], [TimeOfDay.DUSK]: [], [TimeOfDay.NIGHT]: [], [TimeOfDay.ALL]: [Species.RESHIRAM]},
   },
   [Biome.PLAINS]: {
     [BiomePoolTier.COMMON]: {
@@ -5126,11 +5137,13 @@ export const biomeTrainerPools: BiomeTrainerPools = {
       ]
     ],
     [ Species.RESHIRAM, Type.DRAGON, Type.FIRE, [
-        [ Biome.VOLCANO, BiomePoolTier.BOSS_ULTRA_RARE ]
+        [ Biome.VOLCANO, BiomePoolTier.BOSS_ULTRA_RARE ],
+        [ Biome.TOWN, BiomePoolTier.BOSS_CONDITIONAL_ULTRA_RARE ]
       ]
     ],
     [ Species.ZEKROM, Type.DRAGON, Type.ELECTRIC, [
-        [ Biome.POWER_PLANT, BiomePoolTier.BOSS_ULTRA_RARE ]
+        [ Biome.POWER_PLANT, BiomePoolTier.BOSS_ULTRA_RARE ],
+        [ Biome.TOWN, BiomePoolTier.BOSS_ULTRA_RARE ]
       ]
     ],
     [ Species.LANDORUS, Type.GROUND, Type.FLYING, [
diff --git a/src/field/arena.ts b/src/field/arena.ts
index e8cc98c0a..87fbb8c37 100644
--- a/src/field/arena.ts
+++ b/src/field/arena.ts
@@ -1,5 +1,5 @@
 import BattleScene from "../battle-scene";
-import { BiomePoolTier, PokemonPools, BiomeTierTrainerPools, biomePokemonPools, biomeTrainerPools } from "../data/biomes";
+import { BiomePoolTier, PokemonPools, BiomeTierTrainerPools, biomePokemonPools, biomeTrainerPools, biomeConditions } from "../data/biomes";
 import { Biome } from "../data/enums/biome";
 import * as Utils from "../utils";
 import PokemonSpecies, { getPokemonSpecies } from "../data/pokemon-species";
@@ -68,13 +68,24 @@ export class Arena {
     const overrideSpecies = this.scene.gameMode.getOverrideSpecies(waveIndex);
     if (overrideSpecies)
       return overrideSpecies;
-    const isBoss = !!this.scene.getEncounterBossSegments(waveIndex, level) && !!this.pokemonPool[BiomePoolTier.BOSS].length
-      && (this.biomeType !== Biome.END || this.scene.gameMode.isClassic || this.scene.gameMode.isWaveFinal(waveIndex));
-    const tierValue = Utils.randSeedInt(!isBoss ? 512 : 64);
+    // const isBoss = !!this.scene.getEncounterBossSegments(waveIndex, level) && !!this.pokemonPool[BiomePoolTier.BOSS].length
+    //   && (this.biomeType !== Biome.END || this.scene.gameMode.isClassic || this.scene.gameMode.isWaveFinal(waveIndex));
+    const isBoss = true; // OVERIDE
+    // const tierValue = Utils.randSeedInt(!isBoss ? 512 : 64);
+    // let tier = !isBoss
+    //   ? tierValue >= 156 ? BiomePoolTier.COMMON : tierValue >= 32 ? BiomePoolTier.UNCOMMON : tierValue >= 6 ? BiomePoolTier.RARE : tierValue >= 1 ? BiomePoolTier.SUPER_RARE : BiomePoolTier.ULTRA_RARE
+    //   : tierValue >= 20 ? BiomePoolTier.BOSS : tierValue >= 6 ? BiomePoolTier.BOSS_RARE : tierValue >= 1 ? BiomePoolTier.BOSS_SUPER_RARE : BiomePoolTier.BOSS_ULTRA_RARE;
+    const tierValue = 0; // Utils.randSeedInt(!isBoss ? 512 : 128); OVERRIDE
     let tier = !isBoss
       ? tierValue >= 156 ? BiomePoolTier.COMMON : tierValue >= 32 ? BiomePoolTier.UNCOMMON : tierValue >= 6 ? BiomePoolTier.RARE : tierValue >= 1 ? BiomePoolTier.SUPER_RARE : BiomePoolTier.ULTRA_RARE
-      : tierValue >= 20 ? BiomePoolTier.BOSS : tierValue >= 6 ? BiomePoolTier.BOSS_RARE : tierValue >= 1 ? BiomePoolTier.BOSS_SUPER_RARE : BiomePoolTier.BOSS_ULTRA_RARE;
+      : tierValue >= 40 ? BiomePoolTier.BOSS : tierValue >= 12 ? BiomePoolTier.BOSS_RARE : tierValue >= 2 ? BiomePoolTier.BOSS_SUPER_RARE : tierValue >= 1 ? BiomePoolTier.BOSS_ULTRA_RARE : 
+        biomeConditions[this.biomeType](this) ? BiomePoolTier.BOSS_CONDITIONAL_ULTRA_RARE : BiomePoolTier.BOSS_ULTRA_RARE;
+    console.log("this.scene: " + this.scene);
+    console.log("this.scene get party " + this.scene.getParty());
+    console.log("biome condition: " + biomeConditions[this.biomeType](this));
     console.log(BiomePoolTier[tier]);
+    console.log(this.pokemonPool);
+    console.log(this.pokemonPool[tier]);
     while (!this.pokemonPool[tier].length) {
       console.log(`Downgraded rarity tier from ${BiomePoolTier[tier]} to ${BiomePoolTier[tier - 1]}`);
       tier--;