Darth Nightmaricus

Darth Nightmaricus was the first recorded Sith Lord, and was the founder of the Sith civilization on Korriban. He is one of only two known members of his species, the other being Jedi Master Salvius, his brother, who was the founder of the Jedi Order and the leader of the Ashla. Both were immortal, and had eight arms, but Nightmaricus had two cybernetic arms which he created from the Dark Side of the Force.

Birth of the Sith
Around the year 100,000 BBY, the being who would later take the title of Darth Nightmaricus arrived on Korriban, and helped create the Sith civilization. He later fell under the sway of the dark side of the Forrce, and was abandoned by his brother Salvius, who strongly favored the light side, leading him to found the Ashla, the Jed'aii Order, and the Jedi Order circa 26,000 BBY. Salvius would later have great significance for the Jedi: He trained Jedi Grand Master Yoda. Darth Nightmaricus disappeared around 30,000 BBY, during the Rakatan Infinite Empire. He trained a Rakatan apprentice, Darth Void, who he made immortal using the Dark Side.

Imprisonment
When the Jedi Temple was built circa 4,000 BBBY, 30 Jedi Masters, led by Salvius, imprisoned Nightmaricus there, forcing him to wander the halls and be part of the Jedi Trials. 15 of the Jedi  perished in the act. Most students whose Trials he was a part of thought him to be a vision. He only revealed the truth to a few beings: Galen Marek, who visited the Jedi Temple numerous times throughout his life, Maulkiller, several clones of Galen Marek, Lord Starkiller, in his own reality and the primary one, and Guybrush Threepkiller, a Lurmen-Starkiller hybrid clone. Galen Marek and Lord Starkiller both encountered him during their first three trials, and Lord Starkiller encountered him a fourth time in the primary reality during his final trial.

Escape
In the year 0 BBY, shortly before the destruction of the Death Star, during Lord Starkiller's final trial, Starkiller revealed that nineteen years earlier, the Jedi Temple was ransacked under orders of Darth Sidious, and that Sidious had most of the Jedi murdered and had declared himself Emperor. Nightmaricus, realizing he was now free, escaped, after being defeated by Lord Starkiller.

Duel  on Densus
Nightmaricus began to search for his brother Salvius, where he found Masters Windu, Kota, Kcaj, Salvius, the spirits of Coleman Trebor, Kento Marek, and the original Galen Marek, and three clones of Marek. He dueled Salvius, taunting him, telling him his precious order had been doomed from the start, calling him a failure and said he was ashamed to have a brother.

The Jedi overpowered him, and he fled into space, taking Lord Starkiller, who had arrived there to fulfill the mission that his master in his own reality had sent him to do, and which his master in the main reality, both Darth Sidious, had sent him to do, kill Coleman Kcaj, and took him in as an apprentice. They fled Densus, and headed to an unknown location.