Lycanthropy

A condition in which someone will transform into a somewhat monstrous, fully feral version of their species under the light of the full moon. This transformation, while brief, is massively dangerous to those afflicted with it and all people around them, as the afflicted will largely lose their sense of self and be overtaken by an insatiable bloodlust.

In Arathan folklore, it is believed that Lycanthropy (and similarly, Vampirism) originated from great fanged canine beasts known as Lurimin, which are often called Pale Stalkers.