Darth Mortem

Darth Mortem was a Twi'Lek Sith Warrior who reigned prior to and during the Grand Army of the Republic. He was incredibly strong in the force and, until 29 BBY, was Palpatine's greatest warrior.

Life
In 55 BBY, Sakē Dalii was born on Ryloth. In 51 BBY,, he was observed with a very high midichlorian count and was taken to the Jedi Temple on Lothal. There, he was trained by Yoda,, then was trained by Cin Drallig as a padawan, until Sakē secretly ran away from the jedi temple and onto a small X-WING in 43 BBY. He then, while looking for his homeplanet, Ryloth to meet his father again, was the first person to discover Exegol within the past 800 years, and was also the first person to accidentally find a planet in the Unknown Regions. He stayed there for two years after his X-WING crashed. He slowly turned to the dark side (he already was before he arrived, but he was turning more intensely at this point) as he studied Ancient Sith Arts. Eventually, in 41 BBY,, he was approached by someone who called themselves Plagueis. He offered Sakē a life of power, control, and respect. He agreed, and was given the title "Darth Mortem." In 32 BBY, Mortem sensed the chosen one on Naboo. He went to ask Plagueis for instructions, but he was dead (extra info). Plagueis' apprentice, Sidious, would now be the one in control and take the title of Sith Lord. Sidious would try to make Mortem stronger, by making him unleash his rage. In 30 BBY, Sidious sent Sake to  Ryloth. At the same time, he was hiring Jawas to kill Sake's father, who was staying on Ryloth. When Mortem discovered his Father's corpse, he killed 82 percent of the Jawas. One year later in 29 BBY, he was sent on a mission to Carnelion IV to either kill the Chosen One or turn him to the dark side. He was outmatched by his master, Obi-Wan Kenobi, which forced him to run away back to Coruscant. Sidious was very angry, and shocked Mortem with Force lightning. When Mortem got up, Sidious set off an alarm, which sent every single Clonetrooper after him. He was forced to hide on Alderaan until the events of Rogue One,, when he fled to Hoth until 1 ABY,, where he was confronted by Darth Vader. Afterwards, he flew away to see the empire thriving more than ever before, more so than the Death Star could have ever lead him to believe. He had seen a lot, but this was more than he could ever take. Eventually, he began toying with the Light side, trying to harness it into a weapon of rage, of torment, of sorrow, to kill the emperor and defeat the treacherous ways of the Galactic Empire. During the Battle of Endor, he went into the Second Death Star in a stolen TIE Bomber. He now wielded a blue lightsaber and took down every stormtrooper that he could. When he was about to reach the emperor's throne room, the Second Death Star blew up, killing Sake.

Notable Opponents
Qui Gon Jinn (39BBY)

Sifo-Dyas (40BBY)

Dooku (38 BBY)