Sigma Creatures

This is a small mod with very minimal impact on gameplay that very rarely spawns a sigma variant of mobs like the cow, pig, and creeper, that have the face texture replaced with patrick bateman. When these mobs are killed, it plays this (https://www.youtube.com/watch?v=zGf_0dqoaxk) scream sound effect, and spawns a hostile but not too strong patrick bateman mob that chases and tries to kill the player. Thats it.