Tetra-Heaven is the world of myths, ruled by the omnipotent god Zeus. Before the events of the anime, there was a war in Tetra-Heaven between the gods and the demon gods, instigated by Lucifer who wanted to rule Tetra-Heaven. It lasted for a hundred years, and recently ended in the gods' favor. Lucifer and his demon gods (among them Quetzalcoatl) were imprisoned in the Land of Fallen Heaven, but by chance, they found a Gate Card, allowing them to escape into Septpia. They began attacking Septpia and its inhabitants under Lucifer's direction, ending a period of peace that lasted since the war with Monolium. Athena, Venus, Valkyrie, Artemis, and Nemesis all volunteered to travel to Septpia to assist ALCA in fending off the demon gods.