General Grievous is the deadliest Jedi hunter in the galaxy, and one of the antagonists of Star Wars Episode III: Revenge of the Sith, alongside Count Dooku, Darth Vader, and Palpatine. Before his time as the Supreme Commander of the Droid Army, he was once a Kaleesh warrior named Qymaen jai Sheelal. The Kaleesh were at war with the Huk in a conflict known as the Huk War. Qymaen jai Sheelal quickly learned the art of war, specializing in a slugthrower rifle. Quickly amassing a great number of Huk kills, he became a demigod among his people. He would then meet the female Kaleesh Ronderu lij Kummar, a master with the sword. The two became very close before her death at the hands of the Huk. Heartbroken, Qymaen jai Sheelal renamed himself Grievous, and then turned all his anger and grief toward the Huk. Aided by his elite, he forced the Huk off Kalee and then swarmed their world, conquering the Huk homeworld. The Huk turned to the Republic for help, and the Kaleesh were forced back to their own world by the Jedi, and left to starve.

Desperate to help his people, Grievous took a job as an enforcer with the InterGalactic Banking Clan. However, after learning that the Huk had attacked Kalee, he headed home to gain vengeance. IBC Chairman San Hill, after consulting with his ally Count Dooku, leader of the Confederacy of Independent Systems, arranged for a bomb to be placed on Grievous' shuttle, Martyr. The Kaleesh was critically damaged, but lived, and then, Hill arranged for the final stage of his plan. Grievous was reconstructed as a cyborg, and was presented to Dooku as a potential weapon to be used in the upcoming war the Count planned.

Grievous was made Supreme Commander, and then, proceeded to wreak havoc on the Republic for three years in the Clone Wars. The general was trained in the art of lightsaber combat by Dooku, who was also a Sith. Grievous was a quick study, and would soon be recognized as one of the most skilled duelists in the galaxy. Aided by his IG-100 MagnaGuards, Grievous killed many Jedi. He led the Confederacy of Independent Systems in the Battle of Hypori, where his existence was made public. In the many battles, such as the Battle of Falleen, Mission to the third moon of Vassek, and the Battle of Togoria, the Confederacy was victorious thanks to Grievous's leadership. The fearsome cyborg struck fear into the hearts of many with Operation Durge's Lance, a massive strike at the Core.

In 19 BBY, Grievous led the Confederate Navy in the Battle of Coruscant, an attack on the Republic's capital. Grievous killed several Jedi, and took Chancellor Palpatine, leader of the Republic, hostage. However, before his flagship could jump to hyperspace, the Republic Navy arrived. The Chancellor was freed by the Jedi Anakin Skywalker and Obi-Wan Kenobi, who also succeeded in killing Dooku. Grievous fled to the Outer Rim world of Utapau, and attempted to regain control of the war, though the Confederacy had been dealt a great blow with the loss of Dooku. Grievous was killed shortly after arriving in the Battle of Utapau by Obi-Wan Kenobi, and the Confederacy would follow soon after.