Douma

The Infinity Castle is an alternate dimension consisting of endless wooden rooms, halls, and moving corridors. It possesses a warped direction of gravity, allowing demons to stand upright, upside down, or perpendicularly on the walls, or move in physically impossible directions. Its unusual structure and layout as Nakime's Blood Demon Art allows any structure within to shift at her will, though the castle additionally also seems to move on its own. During the final assault against demons by humanity, the castle held many notable battles. These included Doma's clashes with Shinobu, Kanao, and Inosuke, Tanjiro and Giyu battling Akaza, Muichiro, Genya, Sanemi, and Gyomei facing Kokushibo, Zenitsu's duel with Kaigaku, and Mitsuri's and Obanai's skirmish with Nakime. Throughout the castle, numerous lesser demons, all having comparable strength to the Lower Ranks, were also present. These demons were sent to attack anyone, including the rest of the trapped non-Hashira Demon Slayers, as part of Muzan's plan to exhaust them for him to kill more easily. Douma: Doma is a major supporting antagonist of Demon Slayer: Kimetsu no Yaiba. He is a demon affiliated with the Twelve Kizuki, holding the second highest position, Upper Rank Two. Doma is outwardly friendly and cheery, possessing an approachable and charismatic air. Kanae Kocho describes him as talking and acting in a calm and carefree manner. However, in truth, he has psychopathic tendencies and adopts sick beliefs and habits, such as devouring his cult's followers with the belief he is saving them from their suffering and pain by letting them live inside his body.Because of his carefree and waggish persona, he was prone to facetious and inappropriate behavior. Even amongst his fellow demons, he was disliked by Muzan Kibutsuji and Akaza for his casual and childish behavior, and indifference to the strict hierarchy that showed complete and total obedience towards the Demon King.