M-DEUS is an optional secret boss from Tokyo Mirage Sessions ♯FE that can only be fought in a New Game+. He is the true form of King, the Mirage that trades Incenses to Itsuki in exchange for Detritus in the Urahara Arena. King says that he is a Mage Dragon and an ally of Medeus. He can fought by being spoken to at the Arena and selecting the option, "I want to challenge you to a battle." King then takes on his true form of M-DEUS, and the battle begins.