The Sith were an order of Force users who learned the ways of the Dark Side of the Force to become dictators of war and vengeance against the Galactic Republic. They were collectively members of the Sith Order, using their wisdom for power and attack and were known to use lightsabers to defend themselves.
Since the beginning of the conflict between the light and dark, the Sith have been the enemies of the Jedi, like whom the Sith wielded lightsabers, often with a red blade. But while the Jedi fought for peace and prosperity the Sith sought power and conquest, leading to countless battles and many wars between them.
The Sith were created by a fallen Jedi after the Hundred Year Darkness at least 6,000 years before the Clone War. After the fledgling organization was defeated by the Jedi Order, he led his brothers and sisters to the Outer Rim, where they conquered a desert and mountainous planet called Korriban, which would be known as "Moraband" by the time of the Clone Wars. On the planet, the Sith constructed massive temples and tombs in a location known as the Valley of the Dark Lords.
The Sith continued to grow in power, enslaving various peoples and building an Empire. The Jedi Order fought against the Sith and their armies in numerous wars in the days of the Old Republic, both sides constructing massive superweapons powered by kyber crystals. During one of these wars, a Sith Lord built a temple on the planet of Malachor V. The temple was, in fact, a superweapon capable of wiping out life, and when the Jedi learned of it, they invaded Malachor. During the battle, the superweapon activated, turning all of the combatants to stone.
The Sith continued building their empires and fighting the Jedi for thousands of years, while also struggling with internal conflict. After the Sith grew so large and the members squabbled for power, the infighting nearly destroyed the Sith, leading one ancient Sith, Darth Bane, to found a strict mandate all Sith would live by known as the Rule of Two; stating that there could only be two Sith, no more, no less: one to embody power and one to crave it; a Master and an Apprentice. By this rule, the Apprentice would eventually have to kill the Master and the cycle would continue. The Rule of Two ensured the Sith Order survived extinction and allowed them to conspire against the Jedi and the Galactic Republic for a thousand years.
Bane and his apprentice reformed the order in secret, continuing to practice and learn about the Dark side of the Force. Eventually, Darth Bane died and was buried in a tomb in the Valley of the Dark Lords, which would later be visited by Yoda one year before the rise of the Galactic Empire.
In the decades leading up to the Galactic Civil War, the Sith Lord Darth Plagueis took an individual known as Sheev Palpatine as his apprentice. Once Palpatine, who took the name Darth Sidious, gained enough power, the latter killed his master, practicing the Dark Side while masking himself by keeping a strong public image, a senator from Naboo. Later, Palpatine became the Supreme Chancellor of the Galactic Republic. In order to achieve lifelong power throughout the galaxy, Sidious orchestrated the Clone Wars, secretly commanding the Galactic Republic and the Separatist Alliance along with his friend and new apprentice Count Dooku, also known as Darth Tyrannus.
As the Clone Wars came to a conclusion, Darth Sidious managed to convince Anakin Skywalker, a prolific member of the Jedi Order, to turn to the Dark Side, who became known as Darth Vader. Together, master and apprentice destroyed the Jedi, and established the Galactic Empire, an imperialistic regime that hoped to bring order to a chaotic galaxy, with Palpatine and the Sith Order in control. With the help of force-sensitive Inquisitors, most Jedi survivors were hunted down and defeated.
- Though there can only be two Sith Lords at any one time, Darth Sidious and his apprentices have employed several dark side accomplices, such as Asajj Ventress and Savage Opress during the Clone Wars and the Inquisitors after the formation of the Empire. In the latter case, the Inquisitors are not Sith Apprentices.