In the medieval era, Jason o' the Blood, a knight of King Arthur's Camelot, is near-fatally wounded by Morgaine Le Fay. In order to save him, the wizard Merlin binds the souls of Jason and Etrigan, a demon from the Underworld, succeeding in reviving Jason, but also giving him many powers, including immortality. Centuries later, Jason Blood is now a demonologist in Gotham City where he and Etrigan are called upon by an old friend to battle their old enemy, Morgaine Le Fay, who has returned and is on a quest to rule the world.
