EcoSpawn

Many mods add creatures but never set up natural spawning, so you only see them from spawn eggs. EcoSpawn fixes that from plain JSON files you edit yourself.

Habitats are matched by biome tag, not biome name, so swapping Terralith for Biomes O' Plenty won't break them. Tags combine with AND and NOT, so "cold grassland" or "forest but not jungle" actually work.

Includes a full Fossils & Archeology: Revival preset — all 62 creatures placed by ecology. Mammoths on cold steppe, Spinosaurus on warm rivers, marine reptiles in open ocean.

Tune spawn weight, group size, height, light, time of day, water proximity, rarity and crowding without rebuilding anything.

/ecospawn why <mob> tells you exactly which check failed where you're standing.

Works with any mod's creatures — type an entity ID into the config and give it a habitat. Mobs with no rule are never touched

Commissioned for Mesozoa (my modpack) by Saurophilius_rex