Though grieving the loss of one of their own at the hands of King Arthur's assassin, the Four Knights and their companions must press onward. Io, who claims to know where the entrance to Camelot can be found, guides them into the demon realm, a noxious place of danger, hostility…and long-lost friends?! Percival's past still holds some secrets, it seems… But under the demon king's protection, the Four Knights of the Apocalypse find themselves faced with new adventures-and new challenges!