I have tried for a long time now, but can't seem to figure out how to spawn a custom entity in a custom biome.
I tried json, in the modbiomes folder and the modentitygeneration folder. Has anyone done this before and tell me how they've done it?
Or maybe see if there's a fix for my code, have been stuck on this for a long while now.
See code below.

Note that any other mob is spawning fine in the biome, my other mobs (bandit here) spawn fine in other biomes.
The entity I want to spawn in the custom biome (volcano monster), I've also tried to spawn in it in other vanilla biomes and it worked fine.

public class ModEntityGeneration
{
    //entities that spawn in specific biomes
    public static void onEntitySpawn(final BiomeLoadingEvent event)
    {
        RegistryKey key = RegistryKey.create(Registry.BIOME_REGISTRY, event.getName());
        Set types = BiomeDictionary.getTypes(key);

        if (types.contains(BiomeDictionary.Type.PLAINS) || types.contains(BiomeDictionary.Type.HOT) || types.contains(BiomeDictionary.Type.COLD)) // Only spawns in plains
        {
            //Weight of spawn: 100, minimum: 4, max: 6
            event.getSpawns().addSpawn(EntityClassification.CREATURE, new MobSpawnInfo.Spawners(EntityInit.BANDIT.get(), 400, 3, 4)).build();

        }
        if (event.getName().equals(ModBiomes.GRAND_MAGIC_ZONE_VOLCANO.get().getRegistryName()))
        {
            event.getSpawns().addSpawn(EntityClassification.CREATURE, new MobSpawnInfo.Spawners(EntityInit.VOLCANO_MONSTER.get(), 600, 1, 2)).build();
        }
    }

    //entities that spawn in specific structures
    public static void onEntitySpawnInStructure(final StructureSpawnListGatherEvent event)
    {
        if (event.getEntitySpawns().containsKey(EntityClassification.CREATURE))
        {
            boolean isCamp = event.getStructure().equals(StructuresInit.BANDIT_CAMP.get());

            if (isCamp)
            {
                event.addEntitySpawn(EntityClassification.CREATURE, new MobSpawnInfo.Spawners(EntityInit.BANDIT.get(), 200, 5, 5));
            }
        }
    }
}

public class ModBiomes
{
    public static final DeferredRegister<Biome> BIOMES = DeferredRegister.create(ForgeRegistries.BIOMES, Main.MODID);

    public static final RegistryObject<Biome> GRAND_MAGIC_ZONE_VOLCANO = BIOMES.register("volcano_zone", () -> makeVolcanoBiome(() -> ModConfiguredSurfaceBuilders.GRAND_MAGIC_ZONE_VOLCANO, 0.18f, 0.15f));



    private static Biome makeVolcanoBiome(final Supplier<ConfiguredSurfaceBuilder<?>> surfaceBuilder, float depth, float scale) {
        MobSpawnInfo.Builder mobspawninfo$builder = new MobSpawnInfo.Builder();
        DefaultBiomeFeatures.farmAnimals(mobspawninfo$builder);
        DefaultBiomeFeatures.commonSpawns(mobspawninfo$builder);
        mobspawninfo$builder.addSpawn(EntityClassification.MONSTER,
                new MobSpawnInfo.Spawners(EntityType.BLAZE, 45, 7, 10));

        //TODO make it generate
        mobspawninfo$builder.addSpawn(EntityClassification.CREATURE,
                new MobSpawnInfo.Spawners(EntityInit.VOLCANO_MONSTER.get(), 200, 1, 2));


        mobspawninfo$builder.addSpawn(EntityClassification.CREATURE,
                new MobSpawnInfo.Spawners(EntityInit.VOLCANO_MONSTER.get(), 40, 1, 2)).build();


        BiomeGenerationSettings.Builder biomegenerationsettings$builder =
                (new BiomeGenerationSettings.Builder()).surfaceBuilder(surfaceBuilder);

        biomegenerationsettings$builder.addStructureStart(StructureFeatures.RUINED_PORTAL_SWAMP);

        DefaultBiomeFeatures.addDefaultCarvers(biomegenerationsettings$builder);

        DefaultBiomeFeatures.addDefaultMonsterRoom(biomegenerationsettings$builder);
        DefaultBiomeFeatures.addDefaultUndergroundVariety(biomegenerationsettings$builder);
        DefaultBiomeFeatures.addDefaultOres(biomegenerationsettings$builder);
        DefaultBiomeFeatures.addSwampClayDisk(biomegenerationsettings$builder);
        DefaultBiomeFeatures.addDefaultMushrooms(biomegenerationsettings$builder);
        DefaultBiomeFeatures.addDesertExtraVegetation(biomegenerationsettings$builder);

        biomegenerationsettings$builder.addFeature(GenerationStage.Decoration.LAKES, Features.LAKE_LAVA);
        DefaultBiomeFeatures.addSurfaceFreezing(biomegenerationsettings$builder);

        return (new Biome.Builder()).precipitation(Biome.RainType.NONE).biomeCategory(Biome.Category.DESERT).depth(depth).scale(scale)
                .temperature(1.5F).downfall(0.9F).specialEffects((new BiomeAmbience.Builder()).waterColor(-3407872).waterFogColor(-16777216)
                        .fogColor(-65536).skyColor(getSkyColorWithTemperatureModifier(0.8F)).foliageColorOverride(-3407872).grassColorOverride(-3407872)
                        .ambientParticle(new ParticleEffectAmbience(ParticleTypes.LAVA, 0.003f)).skyColor(-65536)
                        .ambientLoopSound(SoundEvents.AMBIENT_CRIMSON_FOREST_LOOP)
                        .ambientMoodSound(new MoodSoundAmbience(SoundEvents.AMBIENT_WARPED_FOREST_MOOD, 6000, 8, 2.0D))
                        .ambientAdditionsSound(new SoundAdditionsAmbience(SoundEvents.AMBIENT_NETHER_WASTES_ADDITIONS, 0.0111D))
                        .backgroundMusic(BackgroundMusicTracks.createGameMusic(SoundEvents.AMBIENT_NETHER_WASTES_LOOP))
                        .build())
                .mobSpawnSettings(mobspawninfo$builder.build()).generationSettings(biomegenerationsettings$builder.build()).build();
    }

    private static int getSkyColorWithTemperatureModifier(float temperature) {
        float lvt_1_1_ = temperature / 3.0F;
        lvt_1_1_ = MathHelper.clamp(lvt_1_1_, -1.0F, 1.0F);
        return MathHelper.hsvToRgb(0.2460909F - lvt_1_1_ * 0.05F, 0.5F + lvt_1_1_ * 0.1F, 1.0F);
    }

    public static void register(IEventBus eventBus)
    {
        BIOMES.register(eventBus);
    }
}

{
  "spawners":
  {
    "creature":
    [
      {
        "type": "blackclover:volcano_monster",
        "weight": 40,
        "minCount": 2,
        "maxCount": 4
      }
    ]
  }
}

First time on the forum, but I think I'm on the right place?

Forgot to mention: Using 1.16