Deathmask (Mephisto, in the American dubbing) was the cancer saint, during the late twentieth century. He was one of the few who knew Saga Gemini, I was disguised as a pope. But Deathmask had a relative ethical position, and not to follow Athena forever (because did not believe that there was an absolute good, set in a God), did not care about the fact, continuing to live by its principles; now, Saga is good and Athena is bad.
Deathmask by having no ethics, did not care about the deaths that he gave the thousands of people murdered during wars in which it was sent. And besides, he imprisoned the souls of those who took his life in Yomotsu, and they were there without falling into the hole that leads to Hell; their heads were on the walls, floor and ceiling of the temple guarding.
Cancer saint was sent to kill Shiryu, but he was saved by Mu of his titled blow: Sekishiki Meikai ha. In Cancer Temple, Mu Shiryu without help, it is hit by Sekishiki Meikai ha, leading to the Yomotsu. After a long struggle, Shiryu plays Deathmask Yomotsu in the hole.
In the fight against Abel Deathmask is revived and decides not to follow the Athena, as always, following the strongest (Abel).
In the fight against Hades, Deathmask repented of his crimes and to help revive Shion to awaken Athena's Cloth