Tet (テト, Teto) is the One True God and resides in a king chess piece. He assumed the title after the eternal war which he won after he obtained the Star Cup before any of the other gods and surpassed their strength despite not participating in the war at all. Tet does not belong to any of the 16 races although the closest affiliation to him would be Imanity. After both Shiro and Sora defeated him in a game of Internet chess, he summoned the siblings to Disboard, under the guise of saving Imanity. To challenge Tet for the title of the One True God, one must collect all pieces of different chess from 16 races. This means that, under the tenth rule of the Ten Oaths, one must defeat or unite all 16 races before being able to play against him.