Cult of Darth Phobos

After being betrayed by her Sith brethren, the Sith Lord Darth Phobos organized a cult devoted to herself. She sent her agents throughout the galaxy, assassinating Jedi and Sith alike. Eventually, Phobos was killed by the combined forces of the Jedi and the Sith, but her cult continued to exist for a long time, disappearing only around the time of the Fourth Great Schism in 2,000 BBY.