Dooku voluntarily left the light side behind and became Darth Sidious' dark side disciple, taking the secret name Darth Tyranus and leading the Separatist army.
Sidious may have given Dooku the title of Darth Tyranus, but because the Jedi Order knew him as Count Dooku, greatly preferring to not indulge his role as a Sith, they continued to call him by that name.
Dooku's lightsaber, also known as Darth Tyranus' lightsaber, or Dooku's Sith lightsaber, was the personal curved-hilt lightsaber of Dooku, the Count of Serenno.
You see, Yoda believe that the curve style of the hill. was aggressive in nature. as it was really only good for lightsaber duels, and at that point in time. all the Sith were gone, so it seemed a bit odd that he would want such a weapon.
Billaba became Windu's Padawan and trained under the Jedi Master in the ways of the Force. During her training, Windu allowed her to study Form VII variant known as Vaapad. She eventually became a Jedi Knight, renowned for her skills with a lightsaber and favored Form III when teaching other Jedi.
Qui-Gon was Dooku's apprentice. Dooku loved Qui-Gon like a son due to their many similarities; both were individualists, idealists, and both had knowledge of the Force that was unique.
Studying Jedi Archive records, Dooku based his new weapon design after the curved hilts that were standard during the heyday of Form II lightsaber combat. The curve allowed the hilt to fit better into his hand, allowing for superior finesse and precise blade control.
Summary. The Sith's yellow eyes reflect their emotions and serve as a visual cue for their dark intentions. While most Sith embrace their demon-like appearance, some, like Count Dooku, don't have yellow eyes because they are motivated by philosophical and political goals rather than rage and conquest.
A political idealist, the corruption in the Galactic Senate—as well as the traditions of the Jedi—disillusioned him, causing Dooku to leave the Order and return to his homeworld, where he reclaimed his title of Count and heritage as a nobleman after overthrowing his corrupt brother, Ramil.
Ventress falls in love with Vos. After Vos is turned to the dark side by Dooku, Ventress ultimately manages to redeem him, but she is killed by Dooku with Force lightning shortly after. Vos later returns Ventress' body to Dathomir so that she may rejoin her fallen sisters in spirit.
A Sith Lord with the ability to cheat death and create life, Plagueis is the mentor of Sheev Palpatine / Darth Sidious, who, in accordance to the Sith's Rule of Two, eventually betrays Plagueis by murdering him in his sleep, taking his place as Sith Master.
Rey Skywalker, also known as Rey Palpatine or simply Rey, was a human female Jedi Master who fought on the side of the Resistance during the First Order-Resistance War. A former scavenger from the planet Jakku, her life was changed by the tumultuous events of the last days of the New Republic Era.
Although Order 66 greatly depleted the Jedi Order's ranks, with an estimated less than 100 Jedi surviving it, it was only the beginning of the Great Jedi Purge, which stretched on for years and claimed the lives of many of the survivors of the initial onslaught.
Even though Kylo Ren uses a red lightsaber, harnesses the dark side of the Force, and wears a cape, he is not a Sith. Because of that, he can never hold the title of Darth. Instead, he was just a chaotic mess of the dark side (until he eventually found his way back to the light).
Finally, Darth Maul himself admitted he wasn't capable of facing Vader alone in Star Wars Rebels. And while the story in question is no longer part of the official Star Wars canon, Darth Vader fought and defeated Maul in comic Star Wars Tales #9.
Sidious revealed to Maul that he did not intend to kill his former apprentice, as he still had use for Maul; it was Sidious' hope that Maul would lead the Sith to Mother Talzin, Maul's mother and the leader of the Nightsisters, so she could be eliminated as a potential threat to the eventual Sith rule of the galaxy.
Sidious himself felt that he and his peers had outgrown the use of lightsabers, and only continued carrying them to mock the Jedi. He ultimately viewed his own lightsabers as little more than an affectation, and rarely wielded them in combat.
Dooku could have not beaten Yoda in Geonosis, meaning that the fight would have ended with Dooku either killed or captured had it continued. At that point, the only two Force-sensitive warriors who could beat Yoda in a fight were Mace Windu and Darth Sidious.
Well, he was surprised. He was promised by Sidious that he would get a pardon in his new Empire and accept his capture 20 min before this. Then Palpatine ordered Anakin to kill him. Dooku was not expecting this at all and was so shocked he couldn't say a word, nor betray Palpatine.
