Nether Fungus

Spawning data tags simply contain a list of Biomes. If you're referring to this list for a Pokemon, please double-check if it has an Anti Condition or Anti Biome. Anti Conditions and Anti Biomes are a way to essentially state: not in this biome/condition, so you'll need to cross-reference them. For instance, if a Pokemon is set to spawn in is_ocean, but has an anti condition of is_cold, it will not spawn in cold oceans.

Our Pokemon spawns are generally based on default Cobblemon configurations with additions to allow the entire dex to spawn in all Minecraft biomes and supported biome mods. Most biome mods are supported such as Terralith, Oh Biomes You'll Go, Incendium, Better Nether, Gardens of the Dead, and The Bumblezone. Other biome mods may also be compatible, provided they label their biomes with data tags.

Nether Fungus Biomes
minecraft:crimson_forest	minecraft:warped_forest	betternether:crimson_glowing_woods
betternether:crimson_pinewood	betternether:mushroom_forest	betternether:mushroom_forest_edge
betternether:old_fungiwoods	betternether:old_warped_woods	byg:crimson_gardens
byg:embur_bog	byg:glowstone_garden	byg:wailing_garth
cinderscapes:luminous_grove	gardens_of_the_dead:whistling_woods	gardens_of_the_dead:soulblight_forest
incendium:inverted_forest