Making Mobs Spawn Only in Certain Biomes or Dimensions

In Control lets you restrict a mob to a biome or dimension so it never appears anywhere else. This is useful for themed worlds, modpack balance, or keeping a dangerous mob out of your starting area.

Build a biome-locked rule

Write a rule with the mob you want to control, a biome filter listing the allowed biomes, and a result of allow. Then add a second rule with the same mob and a result of deny as a catch-all. Order matters: In Control checks rules top to bottom, so the allow rule must come before the deny. If you want the mob in every biome of one dimension, use a dimension filter on the allow rule instead of listing biomes.

Avoid common mistakes

Biome names must match the internal registry names, not the display names — check the log if a rule silently does nothing. If a mob disappears entirely, your deny rule is probably catching it before the allow rule. If it appears everywhere, the allow rule is too broad or the deny rule is missing. Always keep a catch-all deny at the bottom of your file so unexpected spawns do not slip through.