Apprentice Tsume Arvundir
Tsume's father was a Repubic Captain while their mother took care of Tsume and their twin, Kumo.
Both children had snow white hair and bright white eyes. Given the similarities of Echani, especially related ones, most people would have a tough time separating the children even if they had not been twins, but even their own mother mistook them from time to time. At the age of five, both children displayed a connection to the force that was recognized by one of the visiting Jedi on Alderaan; a man named Rumar. Still a Padawan, Rumar had no choice but to leave the children there while he reported his findings to his master on Tython. In the time it took Rumar to leave and return, undercover Imperial soldiers had decided the time was appropriate with the Jedi gone. Simply harming a Republic soldier does nothing, but taking their child wounds them deeper.
Tsume was kidnapped and taken to Dromund Kaas where the ship was greeted by a man in dark robes. It was decided that the child would be the father's undoing. The similarity of the children turned out to be an advantage as the Sith thought that the Echani Captain only had one child. Tsume was taken and brainwashed. The training began soon after: history lessons and combat training. The brainwashing wiped Tsume's memory, but never fully erased their personality. Tsume lived in Kaas City for two decades before being sent to the academy on Korriban. Tsume made few friends on Korriban as that wasn't the intent of the place. Four years after arriving on Korriban, Tsume was among many chosen by a large Sith House, House Reign, to be taken and trained aboard their ship. However, Tsume's mild temperament nearly got them in trouble. A Zabraki Acolyte friend of Tsume's from Korriban turned out to be a Jedi Padawan and was executed for treason. The same almost happened to Tsume, but their brainwashing and training saved them, hiding their Republic ancestry.
While aboard House Reign's flagship, Tsume began studying planetary surveys, topographical maps, military reports and orbital defense displays of Republic planets. This was quickly recognized by one of the Darths within the power structure of House Reign: Darth Rue. Tsume's studies were allowed to continue. One day, however, it was announced that Darth Rue would be leaving the ship to rebuild her own powerbase. Given that she was the only one of higher rank that approved of Tsume's studies, Tsume decided that they would ask to accompany her. Tsume's request was granted and they departed the ship. After arriving at Darth Rue's base, Rue, her apprentices and Tsume were greeted by a friend of Darth Rue's: Darth Exillus. Preparations were soon underway to turn this outpost into a proper base of operations. More Darths soon arrived to join the cause, but the powerbase was already failing. Darth Rue soon vanished and left behind a fractured powerbase. Tsume stayed behind knowing that they had a better chance for an apprenticeship among the remaining Darths than they did if they followed Rue.
Tsume continued their studies as they had aboard House Reign's ship and began uploading their reports on Republic targets, weaknesses and strategies to the archive in the base.
This was recognized and Tsume was made Apprentice of then-Lord Thrakkus. Tsume was commanded to build their own lightsaber by any means.
Tsume figured that the best way to do this was to impress their master by bleeding Jedi crystals. Tsume made their way to Nar Shaddaa and found someone there that they didn't recognize, but recognized them: Jedi Master Rumar. Tsume received two lightsabers from Rumar which they took back with them to remove the crystals and bleed them.
Tsume failed in bleeding the crystals, but didn't know it, soon falling unconscious. Someone bled them for Tsume while they were asleep at the forge. Tsume awoke and constructed their lightsaber thinking they did it all.
Months went on and Tsume continued to do their Master's bidding, as well as making "friends" along the way. Tsume was made a Sith Adept and became one of their Master's tools in the newly formed coalition of Darths.