Quasit

Unlike other demons, quasits are formed when a mortal spellcaster sheds a portion of their own sinful soul to create a familiar or companion. When these quasits outlive their creators, they become free willed and seek methods of returning to the Abyss, a task that requires pledging servitude to more powerful demons, so many quasits instead opt to remain on the Material Plane to promote evil and hope for chance and luck to someday provide them with a method of reaching the Abyss on their own.