Ulic Qel-Droma

Ulic Qel-Droma was, during different times in his life, a Jedi Knight of the Old Republic, a warlord of a secret society, and later a Dark Lord of the Sith. A Human male native of the planet Alderaan, Ulic and his brother Cay were the sons of Lien-Tsai Qel-Droma, a Jedi Master, but trained alongside the Twi'lek Tott Doneeta under Master Arca Jeth at Jeth's praxeum on Arkania. In 4,000 BBY, Ulic was sent with Cay and Doneeta to resolve the centuries-long Beast Wars of the planet Onderon. Initially siding with the citizens of the capital city Iziz, Ulic and his fellow Jedi eventually allied with the Beast Riders of Onderon after learning that Iziz's inhabitants worshipped the dark side of the Force under the leadership of Queen Amanoa. War subsequently broke out between the Queen's forces and those of the Beast Riders, but ended when Ulic's Master Jeth arrived and defeated Amanoa, bringing a short-lived peace to Onderon.
In 3,998 BBY, Amanoa's husband, King Ommin, emerged from hiding to disrupt Onderon's peace by waging war in the name of his ancestor, an ancient Dark Lord of the Sith named Freedon Nadd. Ulic and the Jedi once again fought to defend Onderon, but when Master Jeth was captured by Ommin and Freedon Nadd's spirit, Ulic requested aid from the Galactic Senate. Qel-Droma's help arrived in the form of the Republic navy and a team of five additional Jedi Knights, led by novice Jedi Nomi Sunrider—with whom Qel-Droma would later fall in love. Bolstered by the strength of the navy and Sunrider's innate talent with Jedi battle meditation, Ulic and his comrades rescued Master Jeth, defeated King Ommin and his dark side army, and banished the influence of Freedon Nadd's ghost from the planet forever. In the aftermath of the final battle of the Uprising, Qel-Droma was visited by the spectre of Nadd, who, much to Ulic's surprise, foretold his destiny as a Lord of the Sith.
When the Jedi learned of a political uprising staged in the Empress Teta star system by a newly-formed dark side organization Krath, Ulic was acted as a liaison for the Order and joined the Republic for an assault in Tetan space. However, Qel-Droma was unprepared to deal with the scope of the Krath's powers, Qel-Droma suffered near fatal wounds as he led the Republic into retreat after their defeat against the Tetan usurpers. The Jedi had become increasingly concerned with the galactic threat posed by the Krath, and gathered en masse on the planet Deneba to discuss a course of action. It was here that Qel-Droma unveiled his controversial plan—one that was looked upon unfavourably by nearly all those present—to infiltrate the dark side organization, and attempt to destroy them from within. Before the convocation was brought to an end, the Krath ambushed the gathering with a bombardment of war droids. Qel-Droma fought valiantly alongside his fellow Jedi, but was mortified when Master Jeth was killed after saving Ulic's life. Revenge was then born within Qel-Droma, and he decided to carry out his proposed mission—against the pleas of his brother Cay, and lover Nomi Sunrider. Ulic traveled to Empress Teta and joined the Krath, initially pretending to be a fallen Jedi, and eventually taking the Sith sorceress Aleema Keto as his mistress. However, when he was injected with a rage-inducing poison by Krath warlord Satal Keto, things began to spiral out of control. When his friends came to Empress Teta in search of him, he lashed out with the dark side of the Force and rebuked them, though they vowed to return and rescue him from the influence of the Sith. During that same confrontation, Qel-Droma slew Lord Keto in a fit of rage, who had been named as the responsible party for Master Jeth's death, and assumed his position as warlord of the Krath alongside Aleema. Later, when the Jedi returned and failed yet again to extract Ulic, another of Freedon Nadd's students, Exar Kun, arrived to eliminate the Krath. Qel-Droma engaged him in a duel, but the contest was interrupted by the spirit of a long-deceased Sith, who proclaimed Kun the new Dark Lord, with Qel-Droma as his first apprentice. Qel-Droma united his Krath with the forces of Exar Kun to form the notorious Brotherhood of the Sith, which immediately waged war upon both the Jedi Order and Galactic Republic.
The two nearly succeeded in bringing down the galaxy. Near the end of the war, Ulic encountered his brother on Ossus and dueled him, ultimately killing him. However, this act horrified Ulic, and filled with sadness over what he had done, he abandoned the dark side. Furious at her former love, Nomi Sunrider permanently cut Ulic off from the Force. A broken man, Ulic spent the next decade wandering the galaxy, mourning his brother's loss.
Finally, Ulic was redeemed by Nomi's daughter Vima, whom he had trained to be a Jedi. Shortly after this, his was killed by the spacer Hoggon, after being presumed to still be a threat. However, he became one with the Force, as he had finally come to terms with his actions. 
His spirit however would not remain rested, having on occasion come back to help guide the next generations of Jedi, including Anakin Skywalker and descendant Rhyley Stargazer.
= Foot Note =
This NPC is used within a RESOLUTION Plot and is so part of the RSN Universe of Star Wars lore.