Lycanthropy

Under the "boon" of an ancient entity, people cursed with lycanthrope have their forms contorted into wolf-like monsters under the cover of the full moon.
Lycanthropy is a rare condition that has existed since ancient times. No one truly knows when or where the first case of Lycanthropy appeared, but should one travel deep into the wilderness, one may hear stories told and passed down through generations. Stories and tales that serve as warnings to beware of the night for those who walk under the light of the full moon. They can appear as man or elf, dwarf or dragonkin, then suddenly take the form of a wild beast at the apex of slaughter. Perhaps they could be mistaken for beastkin gone mad, but you would soon learn they are anything but regular beings, driven by a thirst for blood and carnage. Despite the threat they pose, they live on the edge of folklore; this kind of tale is likely the most one would hear of these creatures, with little to no evidence supporting how such a being even comes to be. Few people have even heard of such a thing, as the cases are so rare and scattered.

Long and forgotten legends of a secretive and vindictive spirit, one of immense power and a deep-seated need for power and control. A hunter whose ambition was greater than any other. A spirit known only as the Hunstman, whose true name of Sarith Galo was lost to time millennia ago. For reasons not well understood, this powerful spirit was fond of allowing those who sought their guidance to unleash their "true inner power." Their inner instinctual selves. Galo believed the most truthful and incarnate form of the apex mortal soul was that of the beast of predators. It is this philosophy that is believed to have inspired Galo to forge the curse of lycanthrope, molding unfortunate souls who relinquish themselves to his will into facsimiles of pure primal rage.