Count Dooku

Dooku, full name Jard Dooku a Force-sensitive human male, was a Jedi Master that fell to the dark side of the Force and became Sith Lord Darth Tyranus. 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 is 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 master's plans, but ultimately forgot that treachery was the way of the Sith.

History
Born in 97 BBG during the Age of the Republic, 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. 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.