In his early twenties, Dooku was already capable of executing the Force Lightning attack to combat enemies, and defeated an equally legendary Jedi in Sifo-Dyas with one hand and no vision.

In Attack of the Clones, the whole Clone Army plot is pinned on Jedi Master Sifo-Dyas, but he commissioned the army influenced by Dooku, who, in turn, was influenced by Sidious.

A Jedi mission finds a lightsaber belonging to the long-dead Master Sifo-Dyas, prompting Yoda, Obi-Wan Kenobi, and Anakin Skywalker to begin an investigation into his decade-old disappearance.

These Jedi have become some of the more intimidating figures in Star Wars, either from Dark Side affiliations or sheer power.