The Order of Sith Lords
The Order of Sith Lords, also known as Bane's Sith Order, Banite Sith or simply the Sith, was secretive organisation of Sith Lords that followed the Rule of Two, a Sith philosophy that stated there would be no more than two Sith at a time, one which would be a Sith Master and the other a Sith Apprentice, who would live under the apprenticeship of their Master, until the point that one or the other would kill each other, when the Sith Apprentice challenged the Sith Master for their mantle.
Formed a thousand years before the Battle of Yavin, the Dark Lord of the Sith, Darth Bane orchestrated the destruction of the Brotherhood of Darkness, when it became apparent that the Sith of his time had become weak and stagnant. Following the Seventh Battle of Ruusan, the Order of Sith Lords was founded and began a thousand year plot that culminated with Darth Sidious, whom alongside his Sith Master Darth Plagueis, begun the first stages of the Clone Wars. On the eve of becoming the Supreme Chancellor of the Republic, Sidious murdered Plagueis. Following the death of his Sith Master, Sidious utilized his new position that Plagueis helped to engineer him into and instigated a civil war between the Galactic Republic and Confederacy of Independent Systems, with the latter led by his Sith Apprentice Darth Tyranus. Towards the end of the Clone Wars, Tyranus was slain by Darth Vader, whom subsequently filled the vacant position as Sidious's Sith Apprentice. Together, Sidious and Vader orchestrated the Great Jedi Purge and ended the Clone Wars, where the Confederacy's leadership was massacred on Mustafar and it's droid army deactivated by their executioner, Darth Vader.
At the end of the Clone Wars, Darth Sidious as his alter ego Supreme Chancellor Palpatine utilized the emergency powers awarded to him by the Galactic Senate and declared the New Order, reforming the Galactic Republic into the first Galactic Empire. As the Emperor, Darth Sidious utilized the Clone Army that Plagueis had put into creation a decade prior to the Clone Wars, in order to disband the Imperial Senate. This, combined with the failed plot to reveal potential rebels against the Empire, formed the Alliance to Restore the Republic. This rebellion ended Darth Sidious's reign as Emperor, with his final fall in 11 ABY and the fragmentation of the Order of Sith Lords, with the death of Sidious's Apprentice, Darth Vader in 4 ABY.