As a leader of the droid armies for the Separatists, General Grievous was a cyborg trained in the art of the lightsaber cobat by Count Dooku himself.  Grievous was a ruthless warrior that was committed to the destruction of the Jedi and successfully destroyed several of them and used their lightsabers as trophies from each of the battles.  With strong metal like armor covering the majority of his robot form, Grievous still had vulnerable internal organs that would one day be detroyed and ultimately bring his demise.

General Grievous was first seen on screen in Star Wars Episode III: Revenge of the Sith.  His rise to power began as Grievous and Count Dooku abducted Chancellor Palpatine from the galactic capital on Coruscant.  In an attempt to rescue Palpatine, Obi-Wan Kenobi and Anakin Skywalker set out wth R2-D2 on a mission to save the Supreme Chancellor.  In the end, Count Dooku dies at the hands of Anakin Skywalker and thus transfers command over the Separatist Council to General Grievous.