Fort Revolve (Japanese: 白魔遊幻城, Kanji translation: White Devil Phantom Castle, Romaji: fōto riborubu)[1] is thought to be a water shamanistic spell. It is an original spell of Naga the Serpent.
The caster can control a piece of packed snow and make it fly at will. This can be used for defense, maneuvering the snow to intercept spells, or even to be worn by the caster to act as a piece of armor.