Naga Sadow

Naga Sadow was a male Sith Lord, and renowned dark side magician during the days of the first Sith Empire. Sadow had ancestors among both humans and the Sith species of the planet Ziost. He rose to prominence in the final days of the Sith Golden Age, when Marka Ragnos, the reigning Dark Lord of the Sith, passed away, leaving the mantle of Dark Lord vacant. During Ragnos' funeral, Sadow engaged in a duel with rival Sith Lord Ludo Kressh for Ragnos' title, only to have their contest ended by the spectre of the deceased Dark Lord himself. After a brief admonition, the ghost departed while issuing a warning to both Sadow and Kressh, stating that the fate of the Sith Empire hung on the balance of their decision on how to proceed with leadership of the Sith people.
However, the unexpected arrival of two Hyperspace-traveling siblings on Korriban, Gav and Jori Daragon, immediately spurred Sadow's progressive nature. Seeing them as passports to an ideal opportunity for conquest of the Galactic Republic from which they originated, Sadow masterminded a plot that resulted in his ascendance to Dark Lord of the Sith, with many of the lesser Sith Lords swearing fealty to him—save Ludo Kressh and those loyal to him. Kressh in turn gathered his own followers, and made an attempt on Sadow's life, striking at his decoy-fortress on the planet of Khar Delba in error. Kressh's attack was thus fruitless, and his forces were defeated by those of Naga Sadow. Now the undisputed ruler of the Sith Empire, Sadow allowed one of the alien travelers, Jori, to return home in feigned earnest; he was in truth allowing the girl to unwittingly lead his forces directly to the Republic.
Daragon made her way to the Empress Teta system to warn the Republic of the impending Sith invasion, but the Sith fleet emerged from hyperspace before an ample defense could be mustered. Leading the Sith forces from his personal meditation sphere, Sadow gave command of his flagship to Gav Daragon, and the Sith launched attacks against various unsuspecting Republic worlds. However, Sadow was betrayed by Gav when he fired upon the Dark Lord's sphere and interrupted his meditations, causing the illusions he had been projecting to fade. The tide of battle immediately turned in favor of the Republic as the bulk of Sadow's forces simply disappeared, and the war ultimately lost to the invaders. His fleet in shambles, Sadow then fled back to Sith space, where he engaged in a final battle with Ludo Kressh, one that resulted in the latter's death. Under the forces of Empress Teta, the Republic followed Sadow to his Empire, in an attempt to destroy the remaining Sith, once and for all. Sadow fled to Yavin 4 with his remaining Massassi warriors, where he hoped to rebuild the Empire.
Failing in his goal, Sadow entered a Sith sarcophagus to wait for someone to seek him out to continue the Sith Empire. 600 years later the fallen Jedi Freedon Nadd arrived on Yavin 4, awakening Sadow's spirit. After he learnt all he could, Nadd destroyed Sadow's spirit and left Yavin 4 to rule over the planet Onderon as the new Dark Lord of the Sith. 
It would be over four thousand years later that Sadow would again rise from the dead, this time awoken by Kileo Dimoh who had the taint of Sadow's former apprentice surrounding her. His spirit would engage in a constant conflict with the spirit of Vodo-Siosk Baas within the temple until 7 ABY when Kileo and Rhyley Stargazer returned to the temple. Though Sadow was able to control the body of Kileo, her mind fought against the illusions the Sith Master created and with Stargazer and Baas, finally dispelled the essence of the Sith Lord.
= Foot Note =
This NPC is used within a RESOLUTION Plot and is so part of the RSN Universe of Star Wars lore.