Dark Underlord

In around 1750 BBY during the New Sith Wars, a dark side spirit known as the "Dark Underlord" reigned as a Dark Lord of the Sith. A shadowy figure of unknown origins, he was rumored to have been summoned from the realm of chaos. The Dark Underlord was a male Sith warlord who rose to leadership over the revived Sith Empire, establishing an alliance known as the Black Knights. Based on the planet Malrev IV, the Underlord led a bloody campaign against the Galactic Republic and the Jedi Order, terrorizing the galaxy's Outer Rim Territories. These activities provoked the ire of Murrtaggh, a Jedi Master who—aided by Mandalorian mercenaries—misdirected the Black Knights in a surprise attack against the Underlord's base of operations. This drove the Dark Underlord into a personal confrontation with Murrtaggh himself, during which the Sith Lord met his ultimate demise against the Jedi Master.

Text and facts from the “Dark Underlord” article on Wookieepedia, licensed under CC BY-SA 3.0. Modified for this site.