Set Harth was a Dark Jedi of the Old Republic, infamous throughout the galaxy and somewhat of an urban legend to the galaxy's citizens. Born shortly before Sith Lord Kaan waged war against the Jedi Order, Set Harth was raised at the Jedi Temple on Coruscant where he developed a reputation for hostility. Set Harth embraced what the Jedi hoped to train out of their students, that is, he embraced a preference of violence over negotiation and gave little consideration to the peaceful tenets of the Jedi Code. When he was of age, Set Harth was accepted and the Padawan apprentice of Jedi Master Aru-Wen, who hoped to rein in the boy's aggressive tendencies.
Unfortunately, Aru-Wen was called to war when Jedi Master Hoth established his Army of Light to meet the threat of Sith Lord Kaan and the Brotherhood of Darkness. Left without a Maser, Set Harth continued the instruction on his own, but without a Master at his side, Set Harth's view of the Force and its application became more and more belligerent. After the Battle of Ruusan, which decimated Jedi and Sith forces alike and killing Master Aru-Wen, Set Harth left the Jedi Academy to continue his study of the Force in the galaxy at large. At the Jedi Temple, Harth always felt like the Jedi Masters were keeping certain information from him. When he left, his goal was to discover these secrets of the Force.
Becoming a seasoned traveler, Set Harth traversed the galaxy, looking for locations strong in the Force and seeking out Sith artifacts that might give him insight into forbidden knowledge. His travels eventually took him to Ruusan seeking out a particular Sith artifact. However, on the surface, Set Harth discovered a Sith warrior who had survived the previous war also seeking the artifact. In a decrepit Sith armory, Set Harth battle this warrior for the artifact eventually proving to be the victor. However, it was that day on Ruusan that Set Harth's journey to the Dark Side became complete. Although he did not realize it, Set Harth had given into his anger during the battle, and this incident marked Harth's transformation into a Dark Jedi.