"Jedi Master Sifo-Dyas is still a leading member of the Jedi Council, is he not?"
About this creation
Sifo-Dyas was a Jedi master and good friend to Dooku. When Dooku was seduced by the Dark Side he was tasked with murdering his old friend. Dooku kept the body frozen for many years until he used the Jedi's blood to help in the re-building of Grievous. When Grievous was complete Dooku gave him Sifo-Dyas' lightsaber as a gift.