Sith Quadrumvirate

The Sith Quadrumvirate was an Empire that existed in the years following the Mandalorian-Jedi war. It was the final incarnation of the original Sith before the Fall of the Old Republic. Following the escape of 4 dark side-wielding sisters from Mandalorian custody, they travelled to Moraband where they performed a ritual that called upon all dark side users to their command. After 6 years of gaining strength in secret, the last Jedi-Sith war took place. It would be the final conflict between the Jedi and the Sith for 1000 years until the Clone Wars and the rise of the Galactic Empire.

During the Moraband Cataclysm Darth Syto and her lover, Darth Echdys, betrayed the leader of the Quadrumvirate, Darth Kaenus. The duel that ensued killed the rest of the Royal Sith Council including Darth Lachron and Darth Nexis. The only survivor of the infighting was Darth Bane. He would go on to establish the Rule of Two and rebuild the Sith Order in secret for the next 1000 years while the Republic enjoyed relative peace.