The Rakatan Infinite Empire
The Rakata conquer other worlds using slave labor and technology tied to the dark side of the Force. Their state collapses around 25,200 BBY. That decline explains why later civilizations keep finding powerful artifacts whose purpose nobody remembers anymore.
The best-known Rakatan creation is the Star Forge - a huge automated shipyard near Lehon that draws matter and energy from the local star and can turn out ships and weapons without pause. Its workings are rooted in the dark side, so the Forge also affects those who control it. This is where the Rakatan Star Maps sought by the heroes of KOTOR ultimately lead.