Enmu

Enmu (魘夢) is a major antagonist in Demon Slayer: Kimetsu no Yaiba, serving as the main antagonist of the Mugen Train Arc. He was a demon serving directly under Muzan Kibutsuji, as the Lower Rank One of the Twelve Kizuki. He was the last of the Lower Ranks to be left alive and then attacked a train with two hundred passengers, with Demon Slayers among them, whom he got tasked to kill the Hashira by Muzan Kibutsuji. Enmu uses his hypnotic powers to put those who confront him to sleep, and gives them sweet dreams while he very quietly tries to kill them without making them suffer.