The Polyhedron Fortress is a fortress in space, used to store objects of great value.
The fortress is spherical in design, with various towers sticking out on all sides. On the outside, it is equiped with missile launchers that fire homing missiles. On the inside, various traps are in place to keep out thieves. These include hallway with walls that can close and squeeze anyone inside. The vaults themselves are guarded by Zargon Slugs.
In "The Notorious Mrs. Goodspeed", Sheryl Goodspeed tricks the Team Squad into helping her break into the fortress, to steal a red diamond. Supposedly because it's an heirloom that was stolen from the real owner, and which they were going to take back, but in reality because it containd one of the Dimensional Keys.
