Grievous, born as Qymaen jai Sheelal, was the cyborg Supreme Commander of the Droid Army of the Confederacy of Independent Systems for most of the Clone Wars. Grievous was originally a Kaleesh from the planet Kalee, where he lived his early life. During the Kaleesh conflict against the Huk, 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 eventually met the female Kaleesh Ronderu lij Kummar, a master with the sword. The two became very close before Kummar's death at the hands of the Huk. Heartbroken, Qymaen jai Sheelal renamed himself Grievous and turned all his anger and grief toward the Huk. Aided by his elite, he forced the Huk off Kalee and then swarmed their homeworld, conquering them. The Huk turned to the Galactic Republicfor 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. IGBC Chairman San Hill, after consulting with his ally, Separatist Head of State Count Dooku, arranged for a bomb to be placed on Grievous' shuttle, Martyr. The Kaleesh was critically injured, but lived, and 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 that the count had planned against the Republic.
After being made Supreme Commander, Grievous proceeded to wreak havoc on the Republic for the three-year–span of the Clone Wars. The general was trained in the art of lightsaber combat by Dooku himself, who was also a Sith Lord. Grievous was a quick study and eventually came to be recognized as one of the most skilled duelists in the galaxy. Aided by his IG-100 MagnaGuards, Grievous killed many Jedi, and led the Confederacy to victory in many battles. Quickly gaining a reputation as a savage, merciless brute as well as a tactical genius, the cyborg struck fear into the hearts of many with his flagship, the ion cannon–armed Malevolence, as well as Operation Durge's Lance, a massive strike at the Core Worlds.
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 Supreme Chancellor Palpatine, leader of the Republic, hostage. However, before the general's flagship, Invisible Hand, could jump to hyperspace, the Republic Navy arrived, and the Chancellor was freed by Jedi Knights Obi-Wan Kenobiand Anakin Skywalker, the latter of whom was also successful in killing Dooku. Grievous fled to the Outer Rimworld 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 in the Battle of Utapau by Kenobi, and the Confederacy fell soon after. At some point after Grievous's death, his body was used to create the droid warrior N-K Necrosis, who considered himself to be the reincarnation of Grievous. However, the droid was killed shortly after his creation by several spacers.