Many years ago The Citadel Homeworld was attacked by their mortal enemies, the Psions. During that war the homeworld moons was shattered and turned into a ring of free-floating boulders. Boulders that the Citadel hollowed out, built upon and finally armed. Now the Citadel Homeworld is ringed by an impenetrable fortress that no one, not even the Psions, have been able to breach.