Of unknown origin and meaning, the Fourth Wall dominates the northern horizon, looking rather conspicuously like a gigantic construction of brick and mortar. Wide cracks riddle the surface of the Fourth Wall, revealing glimpses at another world that is at once both alien and entirely uninteresting. Though the best astrologers have attempted to dissect individual pieces of the Fourth Wall with powerful Perception magic, they always appear to be just another brick in the wall.
Note: The enigma of the Fourth Wall is never taught to Moon Mages. Additionally, the Fourth Wall is visible only on April Fool's day. It is a joke and is not considered a canonical celestial object within the game's lore.