Custom Mob Spawner is a helper utility for mod animals Mo' Creatures. It allows you to set the spawn location of the mobs. Without Mo' Creatures this mod is useless and there's nothing you can do

Mod Mo' Creatures adds more than 60 new mobs and animals you can tame and even ride them on horseback. In addition to the usual beasts mod adds and mystical creatures and monsters. To work this mod you will need to install Forge and CustomMobSpawner for your version of Minecraft