What is Count Dooku’s Sith name?

The story behind the answer

After leaving the Jedi Order, Count Dooku fell to the dark side under Darth Sidious and adopted the title tied to his covert alias in Attack of the Clones—he hires Jango Fett as “Tyranus” and leads the Separatists. Don’t confuse him with the distractors: Darth Sidious is Palpatine (Dooku’s master), Darth Plagueis was Sidious’s master, and Darth Bane founded the Rule of Two millennia earlier.

A former Jedi Master and Yoda’s onetime apprentice, Dooku becomes the political face of the Confederacy while secretly engineering the Clone Wars. His elegant Form II (Makashi) dueling style and curved-hilt lightsaber reflect his aristocratic Serenno heritage and mastery of precise, one-on-one combat.