Sith Eternal

The Sith Eternal is a Sith cult founded and led by Emperor Palpatine and the main antagonists of the final installment of the Star Wars sequel trilogy Star Wars: The Rise of Skywalker.

They were formed by a revived Emperor Palpatine after the Galactic Empire was defeated at the Battle of Endor and the Death Star II was destroyed. They used the First Order as a distraction while they built up a massive fleet of Star Destroyers outfitted with Death Star technology to once again conquer the galaxy. They later merge with the First Order to form the Final Order and invade the galaxy to establish a New Galactic Empire to reign supreme.

History
Following the defeat of the Galactic Empire at the Battle of Endor, which saw the destruction of the Death Star II, Palpatine retreated into the Unknown Regions with a collection of his followers to rebuild his fleet. From the shadows he formed the First Order to antagonize the New Republic and distract from his real plans, to build up an extremely large fleet of Star Destroyers and use them to swoop in and conquer the galaxy once more.