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. 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, using her biwa she can manipulate the position of any demons inside.