To make a hellcat, any kind of cat (normal/kitten/lazy/wily) must be taken into Evil Dave's Basement. After killing a sufficient number of hellrats it will become a hellcat. When overly fed it becomes an overgrown hellcat. It can no longer catch rats when it becomes an overgrown hellcat.
Your hellish pet cat!!
This Data was submitted by: Eragon4life, Jakesterwars, Radmite, and Alfawarlord.