A hellcat is a special variant of a normal cat that can be accessed after starting the Freeing Evil Dave sub-quest of Recipe for Disaster. During the quest, players must visit Evil Dave in his mother's basement. There they must use their cat to kill Hell-Rats, which have stolen his mother's special coloured spices which are needed to make the spicy stew to free him. After your cat catches seven rats, it will become corrupt by the demonic nature of the rats and will suddenly transform into a hellcat. Also, killing the Hell-Rat Behemoth results in turning your cat into a hellcat immediately. Note that any existing hellcats may need to be placed in a menagerie, or transformed back in to an ordinary cat, in order for subsequent cats to be transformed. A hellcat can be turned back into a normal cat of the same colour it was before the conversion at any time by feeding it a bucket of milk.
A cat at any stage of growth can be a hellcat, and a cat that has become a hellcat will continue to age as normal. While it is impossible to convert an overgrown cat into an overgrown hellcat, since overgrown cats cannot catch rats, players can get an overgrown hellcat by allowing a hell-kitten or adult hellcat to age into an overgrown hellcat. Players who have completed Ratcatchers can also get wily and lazy hellcats, either by using their wily or lazy cats to catch Hell-Rats, or by taking an overgrown hellcat to Felkrash and having her train it.