Riastrad

A curse laid upon people who tamper with their physical forms through magical mutation. Also simply called an abomination.

Causes the inflicted to transform into a grotesque monster, degrees vary from hulking brute to something beast-like, losing control of themselves and usually going berserk and attacking everything around it. Though some cases this other form has shown signs of intelligence, will and agenda of it's own independent of original form's (jekyll and hyde.)