The Retribution is an almighty force sealed away within the land of Riviera that had the power to completely annihilate it. During the events of Riviera: The Promised Land, Ein and Ledah were sent on a mission to actuate the Retribution, as the Magi feared the resurgence of demons in Riviera as a catalyst for another Ragnarok. Ursula, Riviera's protector, took measures to avoid its activation, which resulted in Ein's abduction, thus turning the tides in her favor.
Initiating the Retribution involved the unbinding of Seth, which required countless sacrifices. It could be that Seth herself is the destructive power that would destroy the land of Riviera.