Formed thousands of years before the Clone Wars, the Sith were the ancient enemies of the Jedi Order. Established by a rogue Jedi during the Hundred-Year Darkness, the Sith sought further knowledge and power through learning the dark side of the Force. Eventually, this Jedi was able to amass a sizable following, all of whom adhered to this new philosophy that embraced the dark side. This schism in the Jedi Order led to a civil war where the Jedi and the newly-founded Sith Order, once brothers and sisters in the Force, fought against one another for power. The war ended in the defeat of the Sith, who fled from known space. Unbeknownst to the Jedi, however, the Sith settled on Moraband, a world of red sands, where they rebuilt in secret and waited for another chance to strike.
