Curse of the Medusa

A person cursed in this fashion will slowly transform into a medusa. This curse usually comes from bargains made with devils and demons: a mortal might have been asking for beauty or eternal life, but instead was granted the terrifying form of a medusa. Sometimes, ancient fey creatures such as hags will transform a victim into a medusa, often simply for amusement.
The transformation can be stopped with divine magic, but without intervention the victim will transform within a few weeks.