"I'm no errand boy. And I am not in this war for Dooku's politics. I am the leader of the most powerful droid army the galaxy has ever seen."
"An army with no loyalty, no spirit, just programming. What have you to show for all your power? What have you to gain?"
"The future! A future where there are no Jedi."―Grievous and Obi-Wan Kenobi^[​9]
Grievous, born Qymaen jai Sheelal, was a Kaleesh male warlord who served within the military forces of the Confederacy of Independent Systems as a commanding officer during the Clone Wars in the final years of the Republic Era. In addition to his position as a general within the Separatist Droid Army, the Kaleesh held the title of Supreme Martial Commander of the Separatist Droid Armies throughout the duration of the war, in which he led countless engagements against the Republic's Grand Army. Recognized for his ruthless tactics and extensive cybernetic enhancements, Grievous utilized the Separatist Droid Army and his adept combat skills to instill fear throughout the galaxy as he traveled to and invaded planets, while also engaging numerous Knights of the Jedi Order, his sworn enemies.

A native of the Kalee, a planet within Wild Space, Sheelal grew to become a fearsome warrior and warlord of his people. He gained an aptitude for warfare and battle tactics during the Kaleesh's war against the Yam'rii people of the planet Huk, as Sheelal adopted the moniker Grievous and began conquests offworld conquests, his bloody reputation eventually reaching the ears of the Sith Lords Darth Sidious and Darth Tyranus, also known as Dooku, the Count of Serenno. Grievous had been joined in battle for many years by the Kaleesh's greatest warriors, called the Izvoshra. Accompanied by his campanions, he pushed back the Yam'rii from their world, until the Yam'rii sought the Republic for assistance, and hundreds of thousands of Kaleesh were left to starve, which led to the upbringing of the warlord's personal vendetta against the Galactic Republic and Jedi, as they supported the Yam'rii in their war. His grudge led him to ally himself with the InterGalactic Banking Clan, as an enforcer which he was formidable in his activities, which the IGBC soon saw him as one of its most valuable assets. By that time, Count Dooku had noticed Grievous's actions and had big intentions for him as well. Sometime later, members of the Executive Separatist Council led by Count Dooku, in a bid to make Grievous a subservient tool of the Confederacy of Independent Systems, sabotaged his shuttle, resulting in a gruesome crash that left the man on the brink of death. Extensive repairs were made to his destroyed body, forging him into a powerful cyborg warrior consisting of his brain, eyes, and vital organs residing in a mechanical shell.

The reconstructed Grievous became a skilled lightsaber duelist under Dooku's guidance, who trained the Kaleesh in the arts of lightsaber combat and eventually welcomed him into a position as a warrior in the Confederacy. Over time, the Kaleesh warrior made intense alterations and enhancements to his cybernetic body. Grievous was soon granted the rank of general, as well as the title of Supreme Martial Commander of the Separatist Droid Armies, making him the most powerful person within the Separatists, under only Dooku. Grievous wielded his skills as a brilliant military strategist and melee combatant during numerous campaigns against the Republic throughout the Clone Wars while also gaining a reputation for hunting and killing Jedi Knights. He made a habit of claiming the lightsabers of defeated Jedi as trophies and weapons to be used against other opponents. At some point during the war, the cyborg received the nickname of "head clanker" by the Republic's clone troopers due to his cybernetics and position as Supreme Martial Commander. His position and threat level led to his preeminence as one of the Republic's primary targets throughout the course of the war.

Towards the end of the war in 19 BBY, Grievous, under orders from Darth Sidious, launched a daring and unprecedent assault on the planet Coruscant, the capital world of the Republic. In his assault, the Kaleesh managed to take the Republic's Supreme Chancellor, Sheev Palpatine, in reality secretly Sidious himself, captive aboard his flagship, the Providence-class Dreadnought Invisible Hand. However, during the battle, the Chancellor was rescued from the general's grasp by Jedi Generals Obi-Wan Kenobi, Grievous's longtime foe, and Anakin Skywalker, an engagement that also resulted in Dooku's death. Subsequently, Grievous became the de facto leader of the entire Separatist Alliance and immediately withdrew of all remaining reinforcements and fled into the Outer Rim Territories, prolonging the war. Following the Battle of Coruscant, Grievous, succeeding Dooku as the Confederacy's Head of State, retreated to the planet Utapau where he addressed and relocated the members of the Executive Separatist Council to the planet Mustafar under Sidious's orders. However, unknown to the general, Grievous's location on Utapau was betrayed by Sidious, resulting in a Republic invasion of the planet in an effort to bring a decisive conclusion to the war. As a result, following a prolonged chase between the two, Grievous was ultimately slain by his nemesis, General Kenobi, which resulted in the war's conclusion as well as the Confederacy's systematic collapse.