Karen was the priest in the party which set out to kill the Monster Lord Alice XV. Along with Marcellus, Lazarus, and Merlin, she realized too late Alice XV’s wishes of coexistence, although she had been prepared to spread the Monster Lord’s dreams.
However, a young Alice XVI appeared and killed Karen and Merlin out of blind rage. Seeing the woman they both loved being killed, Marcellus and Lazarus founded Ilias Kreuz out of vengeance.