Dooku, a Force-sensitive Serennian human male, was a Jedi Master that fell to the dark side of the Force and became the Dark Lord of the Sith Darth Tyranus during the final years of the Galactic Republic. After leaving the Jedi Order, he claimed the title Count of Serenno and, during the Clone Wars, served as Head of State of the Confederacy of Independent Systems. He was the second apprentice of Darth Sidious, the Dark Lord of the Sith whose plan to conquer the galaxy relied on Dooku leading a pan-galactic secessionist movement against the Republic. As such, Dooku immersed himself in the dark side and worked tirelessly to advance his and his master’s plans, but ultimately forgot that treachery was the way of the Sith.
Born in 102 BBY during the High Republic Era, Dooku was taken by the Jedi Order after being abandoned by his family and learned the Jedi arts as the Padawan of Yoda, the legendary Grand Master of the Jedi Order. A political idealist, the corruption in the Galactic Senate—as well as the traditions of the Jedi—disillusioned him, causing Dooku to voluntarily leave the Order and return to his homeworld, where he reclaimed his title and heritage as a nobleman after overthrowing his corrupt brother Ramil. His former peers believed his decision was misguided but still held him in high esteem. Unknown to the Jedi, however, Dooku not only renounced their ways but his commitment to the light side of the Force as well. Having sworn his allegiance to Darth Sidious, Dooku became the Dark Lord‘s apprentice and adopted the secret name of Darth Tyranus. Throughout the first decade of Sheev Palpatine’s chancellery, Dooku used his resources and charisma to recruit entire star systems to the Separatist cause. At the same time, he oversaw the development of two vast armies that would be pitted against each other in the conflict to come: the Separatist Droid Army, which consisted entirely of battle droids manufactured on Geonosis; and the Grand Army of the Republic, composed by clone troopers bred on Kamino and modeled on the bounty hunter Jango Fett.
After years of maneuvering the galaxy into a state of war, the Clone Wars began when the newly formed Republic Military invaded Geonosis in 22 BBY. As leader of the Separatists, Dooku delegated military authority to a cadre of subordinates personally trained by himself, including General Grievous and Asajj Ventress. While Grievous was trained only in the art of lightsaber combat, Ventress was strong with the Force, affording her the opportunity to learn the ways of the dark side from Dooku. The Sith, however, remained faithful to Darth Bane‘s Rule of Two; and as such, Dooku was compelled to betray his disciple after Sidious became suspicious of his own apprentice’s intentions. Though he sought to replace Ventress with Savage Opress and later Quinlan Vos, Dooku ultimately remained beholden to his master’s will, which would eventually be his undoing. By the third year of the war, Dooku and Grievous succeeded in abducting Chancellor Palpatine (per Sidious’s plan) from the Republic capital of Coruscant in 19 BBY. During the ensuing Battle of Coruscant, he was confronted and defeated by the Jedi Knight Anakin Skywalker, who summarily executed the Count via beheading at the Chancellor’s behest. In the days following Dooku’s death, Palpatine revealed to the Jedi that he was, in fact, Darth Sidious, who betrayed his apprentice in order to replace him with the younger and more powerful Skywalker. With the subsequent fall of the Jedi Order, Sidious consolidated his power upon declaring himself Emperor of the Galactic Empire. As for Skywalker, he succeeded the late Darth Tyranus as Sidious’ third and last apprentice, resulting in his transformation into Darth Vader and proving his slain victim’s words of sensing fear, hate and anger.