Darth Tyranus is Count Dooku>
Count Dooku is a fictional character from the Star Wars universe. He is the main villain of Star Wars Episode II: Attack of the Clones and a supporting villain in Star Wars Episode III: Revenge of the Sith. He plays a substantial role in the "Expanded Universe" of novels, comic books, and video games. In his television and video game appearances, Count Dooku is portrayed by voice actor Corey Burton. In all of his film appearances, which consists of the prequel films and Star Wars: The Clone Wars, he is played by Christopher Lee. Though once a respected and powerful Jedi Master, Dooku became disillusioned with the Jedi Council and became one of the twenty Jedi ever to leave the Order. He then fell to the dark side of the Force, at which time he was initiated into the ways of the Sith by Darth Sidious, who bestowed upon his new pupil the title of Darth Tyranus. He would in turn be replaced by Palpatine's third and most powerful apprentice, Darth Vader.
Here is a great site to go to for more information>
http://starwars.wikia.com/wiki/Dooku
This answer was edited by USAFRET91 135 days ago.
Reason: added website to help
