Douman Ashiya is a prominent antagonist in Fate/Grand Order, particularly featured in the 'Heian-kyo' Lostbelt chapter. Inspired by a real historical figure, he is a powerful onmyouji (sorcerer) in Japanese folklore and serves as a cunning rival to Abe no Seimei. In the game, Douman is a manipulative and enigmatic figure, often orchestrating chaos behind the scenes. His malevolent ambitions and mastery of dark arts make him a formidable foe for the protagonists throughout the story.