Outwardly, the Perplexahedron is a cube. Inside, the planet is a large amount of identical rooms with various death traps developed by the Spaciosapiens. These include shifting rooms, changing gravity, wind tunnels, guards, and the like. Somewhere in there, there’s a secret way into the large world of the Spaciosapiens.
One of the pieces of Map of Inifity was put in it by Professor Paradox. Unlike in Earth-10, the planet was not destroyed.