Estaphis, the strongest among all sages, holds his title as the "Sage of War".
In the Kenjin Doa world, it is thought that no one could go in to large raging battles without permission. At which point, most asked the centaur for his consent and assistance. In repayment of their victory, anyone who played a part in the war of the winning side would offer their souls after they died, to serve the Sage of War rather than hold a place in the waiting room of Heaven or Hell (which most dead are sent to before judgment day)
Along with his great power on the battlefield Estaphis maintains a smithy under a rare structured volcano to the far north-east of nana's meadow. Estaphis forges all the sage's weapons and presents weapons of almost as great of value to those whom he deems especially worthy.
At a young age, an angel who had fallen was to be wed by a valiant man of a great native tribe, but was captured by the enemy whose elder wanted her for his own son, greed in mind. She tactfully escaped desperately trying to find her way back to her love but ended up finding the Sage of War who fought for her freedom. In awe of his handsome features, great strength, nobility and his feelings for her returned, they were betrothed.
Because of her holy blood line and his hands, which were stained with blood of many deaths, the angel had a very hard pregnancy as the two types did not mix. In her womb lay two beautiful twin boys of equal value; but as the pregnancy went on one was said to devour all the holy essence of their angel mother, not leaving a drop left for the other. This caused the selfish one to be born completely angelic (Yang Guardian to the Gates of Heaven) and the other spitefully sinful (Ying Guardian to the Gates of Hell).
Giving birth to a baby as pure evil such as Ying, caused the mother to die shortly after the two were brought into the world. Estaphis, grieved deeply for the death of his love. And though he treasured both his sons and attempted to be a great father to them both, his eyes forever carried a sense of sorrow which he often hides with a mask.