Tundra

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.

Tundra Biomes
minecraft:ice_spikes	minecraft:snowy_plains	terralith:cold_shrubland
terralith:gravel_desert	terralith:rocky_shrubland	terralith:snowy_badlands
terralith:yellowstone	byg:cardinal_tundra	wythers:crimson_tundra
wythers:frigid_island	wythers:ice_cap	wythers:icy_crags
wythers:snowy_tundra	wythers:tundra