Tieflings

Tieflings are humanoids that have been transmogrified on the Convergence Day of the Typhen, in a terrifying, torturous experience akin to taking the mind, soul, and body and flagellating them all simultaneously. They awaken in the gutters of their old home, their old skin shriveled besides them. Usually, horns are scratching at their head for the week leading up to it, until the scratching and tearing removes the skin in a bloody horrible mess and they peel off their old self, revealing the demon within.
This process has been reported to happen to humans, so named Tieflings. It also has happened to elves, so named Fey'ri. Dwarves turn into Maeluth. Halflings turn into Wisplings. Wood Orcs turn into Tanarukk. Visually, they are all affected nearly the same.