What is demon slayer infinity castle?

The Infinity Castle is a key location in the Demon Slayer: Kimetsu no Yaiba manga and anime series. It is the dimensional fortress and headquarters of Muzan Kibutsuji and many of the Twelve Kizuki, specifically the Upper Ranks.

• Structure: The Infinity Castle is an enormous, seemingly endless, and ever-shifting structure. Its architecture is labyrinthine, with rotating rooms, hallways, and pathways that defy logic. The rooms are typically decorated with traditional Japanese aesthetics, such as sliding doors and paper lanterns.
• Function: Its primary function is to serve as a secure base of operations for Muzan and his demon subordinates. It allows Muzan to protect himself and his strongest followers from the Demon Slayer Corps. The castle can be summoned and dismissed at Muzan's will and also by Nakime's Biwa.
• Defense: The castle itself acts as a formidable defense. Its constantly changing layout makes it incredibly difficult for intruders to navigate or escape. Demons guarding the castle use this to their advantage, ambushing and disorienting their enemies.
• Battleground: During the final arc of the series, the Demon Slayer Corps invades the Infinity Castle in an all-out assault against Muzan and the Upper Rank demons. Many important battles take place within its walls, resulting in significant casualties on both sides.
• Weakness: The Infinity Castle's structure and layout are controlled by the Biwa Demon, Nakime.