Catalyn Akumoka

Daughter of a Arch Demon and a Sucubus. Catalyn was a power demon in who made an infamous reputation for herself.
So much so that a group of holy priests and knights fought and sealed her away into the dream world where she became Nightmare Spirit. She plotted for many years to find a way to escape her prison, seeking out a powerful enough host for her to leach power off of to break her seal.