The Sith, collectively known as the Sith Order, were an order of Force users who utilized the dark side of the Force in an effort to gain power over the galaxy. The Sith were the ancient enemies of the Jedi Order and fought numerous wars with them for thousands of years.
Formed thousands of years prior to the Clone Wars, the Sith were the ancient enemies of the Jedi Order. Established by a rogue Jedi, 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 an event known as the Hundred-Year Darkness, in which the Jedi and the newly-founded Sith Order, once brothers and sisters in the Force, fought against one another for power. The civil 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 to wait for another chance to strike.
As the Sith Order grew, they constructed massive temples and tombs on Moraband in a location known as the Valley of the Dark Lords. The Sith built empires on the backs of their slaves and fought wars against the Jedi for control of the galaxy. During these wars, they built massive superweapons powered by giant kyber crystals. During one such conflict, the Jedi and Sith fought on the planet of Takodana. The pirate Maz Kanata later built her castle on top of the legendary battlefield.