Manifolds  
Eons ago, the ancient Progenitors constructed six Planetary Manifolds, which they intended as massive experiments into sentience on a gigantic scale. One of the Manifolds, in the Tau Ceti system, achieved an early sentience, gaining the ability to project undreamt-of power across the galaxy. The "Flowering", as this event was called, engulfed numerous star systems and plunged Progenitor culture into a dark age from which it has not fully recovered. In the ensuing millenia of chaos and fragmentation, the locations of the Six Manifolds were lost.