General Grievous was the Supreme Commander of the Separatist Droid Army during the Clone Wars, serving the will of Darth Sidious (aka Supreme Chancellor Palpatine) under the leadership of Count Dooku.
Born as Qymaen jai Sheelal, Grievous was a warlord from the planet Kalee who learned battle strategies and warfare during his people’s war with the Yam’rii, a technologically advanced alien species from the planet Huk. Because the Galactic Republic supported the Yam’rii in the war, Grievous developed a hatred for the Republic, and by extension, the Jedi, who were the supernatural defenders of the Republic.
Grievous began having his body slowly enhanced with cybernetic parts overtime to make him a more skilled warrior, but after a shuttle crash that nearly killed him and left most of his body severely damaged, he chose to have his body almost entirely rebuilt with cybernetics, making him a cyborg.
After Grievous’s body was rebuilt, there was little left of his original body other than his eyes, brain, and internal organs. His enhancements made him a logical choice to lead the droid army because he understood the droids better than anyone as a cyborg. His enhancements also enabled him to be stronger, quicker, and a better warrior. He even became skilled with a lightsaber under the tutelage of Count Dooku and killed many Jedi. The downside of his enhancements, however, was that they left him with a persistent hacking cough.
How General Grievous dies
After Count Dooku was killed by Anakin Skywalker near the end of the Clone Wars, General Grievous was no longer needed by Darth Sidious, as he was ready to finally end the Clone Wars and execute Order 66 to kill all the Jedi.
Jedi Obi-Wan Kenobi was sent to Utapua, where Grievous was hiding, to engage him. After a battle throughout Pau City that ended at Grievous’s private landing pad where his ship was waiting, Kenobi and Grievous engaged in hand-to-hand combat.
Kenobi, who lacked the enhanced super strength of Grievous, nearly lost but managed to open Grievous’s chest plate. Grievous, noticing this, threw Kenobi off the platform, but Kenobi managed to grab hold of the ledge and, using the Force, summoned Grievous’s blaster and shot his exposed heart. The rest of Grievous’s organic body incinerated at that moment, killing him.