Around 30,000 BBY, a military invasion was initiated by the Killik species against the Outer Rim Territories world of Korriban. The Killiks were originally from the Core Worlds planet Alderaan, and had been moved offworld by the Celestials. At this time, the Sith species resided on Korriban. They had evolved a pre-industrial civilization and had learned to control potent abilities through the Force, notably its dark side, which they were granted with. The Sith repelled the Killiks' invasion of their planet. Both the Celestials and Killiks then vanished from the known galaxy near that year.
Daniel Wallace and Jason Fry introduced the Korriban invasion in The Essential Atlas, a reference book published in 2009.