Count Dooku

Dooku was a Jedi Master who fell to the dark side of the Force and became a Dark Lord of the Sith, known as Darth Tyranus. Born into a noble family on the planet Serenno, he was the heir to vast wealth and the noble title of Count. Dooku was taken by the Jedi Order as a child and apprenticed to Thame Cerulian. As a Jedi Knight, he took Qui-Gon Jinn as his first Padawan, and later trained Komari Vosa. Dooku was a respected instructor in the Jedi Temple and one of the most renowned swordsmen in the galaxy, on par only with Masters Yoda and Mace Windu.

Dooku spent nearly seventy years as a Jedi, but a disastrous battle on Galidraan shook his faith in the Order and the Galactic Republic. He fell under the influence of Supreme Chancellor Palpatine of Naboo, and left the Jedi Order. After learning that Palpatine was secretly the Sith Lord Darth Sidious, Dooku turned to the dark side and became a Dark Lord of the Sith himself, replacing Darth Maul as Sidious's second apprentice. His new master bestowed upon him the Sith title of Darth Tyranus.

Reclaiming his birthright as Count of Serenno and his vast fortune, Dooku conspired with Sidious to force the galaxy into a war that would bring the Sith to power. He forged ties between corporations and planets discontented with the Republic, and became the leader of the Separatist movement that coalesced into the Confederacy of Independent Systems. Thousands of star systems flocked to Dooku's banner and seceded from the Galactic Republic.

As the political leader of the Confederacy, Dooku led the organization against the Republic in a conflict that would become known as the Clone Wars. He recruited and trained four of his greatest warriors to lead the Separatist Droid Army: Durge, the brutish Gen'Dai bounty hunter; Asajj Ventress, Dooku's protégé and Dark Jedi apprentice; General Sev'rance Tann, Chiss commander and Dark Acolyte; and General Grievous, the infamous Jedi-slaying cyborg and droid leader.

The war culminated in a great battle over the Republic capital of Coruscant. In a duel aboard the Separatist flagship Invisible Hand, Jedi Knight Anakin Skywalker defeated Dooku. Skywalker then executed the dismembered and helpless Dooku at the instigation of Supreme Chancellor Palpatine, Tyranus's own Sith Master. He would quickly be replaced by the very man who had killed him, Anakin Skywalker, who would soon fall to the dark side and be transformed into the fearsome Darth Vader.