A Duel Priest or Diak Um (
In the thirtieth century B.C., the Festival of Duality was conduced annually. At that time, the power of the Ultimate God was feared by people. After the Duel Priestess Ish Kiq Goodwin's death in a ritual, Rex and Roman became Duel Priests and took part in the ritual, but the ritual failed.
In the twenty-first century, Roman chose Sect Ijuin as the next Duel Priest, who then took part in a Ritual against Akiza Izinski, a Duel Priestess. Later, Yusei Fudo and Jack Atlas also become Duel Priests, taking part in the ritual Duels inside the Aerial Fortress Seibal.