He eventually pledged himself to the Sith, learning the ways of the Dark Side from the villainous Darth Sidious (better known to the Republic as Sheev Palpatine). Together, Dooku and Palpatine ...
The Republic, with the help of the Jedi, take on Count Dooku and the Separatists ... he sees Master Yoda for counsel. When Darth Sidious executes Order 66, it destroys most of all the Jedi ...