Chameleon

Chameleons imitate an endless variety of monsters. Eating the corpse of a chameleon causes polymorph.

SLASH'EM

If a chameleon polymorphs into a domestic animal, then you can tame it with a treat. In vanilla, it is likely that your pet chameleon will polymorph into something weak and die. In SLASH'EM, because polymorphed monsters return to their natural form upon death, pet chameleons are much more useful! When your pet chameleon would die or self-destruct, it only becomes a chameleon; then can it later polymorph again. A pet chameleon can still die in its chameleon form, but in SLASH'EM you can keep a pet chameleon for much time.

A pet chameleon will from time to time take a form that is strong or useful, so follow every opportunity to tame a chameleon with food.