A Buddhist Onmyouji in the Heian period known as the rival of Abe-no-Seimei. He was called Douma Houshi (道摩法師) or Sangha Douman (僧道満), and given the title of Beautiful Carnivore, the All-Ridiculing (美しき肉食獣). As a Buddhist priest, he was essentially an enemy of the government, and while initially having a cooperative relationship with Seimei from the Bureau of Onmyou, Douman later came to view them as enemies to frequently oppose. He was known for plots such as cursing Fujiwara no Michinaga with the help of Fujiwara no Akimitsu. As it was a time of great mystery, the clashes between the two considered the greatest masters of spells was said to be astounding. Legends even speak of Douman having died several times, but he had mastered pseudo-immortality through learning the secret arts of Hakudou Jounin.

Ascending to the Throne of Heroes, he was known as a Anti-Hero who unscrupulously harmed people and whose death lead society to peace and tranquillity. Alter Ego Douman, or Alter Ego Limbo, summoned by the Alien God was no longer exactly the same existence as the living Ashiya Douman, so he was described as a "caricaturized aspect of the existing Ashiya Douman." While he was not a complete representation of the living Ashiya Douman, the accounts of Murasaki Shikibu implied they shared much of the same inhuman nature and untrustworthiness. He modified himself into a High-Servant by incorporating three component spirits into his Saint Graph. After being defeated and summoned to Chaldea Security Organization, he feigned ignorance, behaving as if he remembered nothing of his prior activities and acting confused over his Alter Ego Saint Graph. As he was in reality summoned with the records of having antagonized Chaldea, it was unknown if it was a karmic bond tying his fate to Chaldea, the Greater History of Man summoning him without taking history into account, or even the wish of Douman himself despite there being no confirmation of summonings being influenced by the wills of Heroic Spirits.

(Source: TYPE-MOON Wiki)