While one of Star Wars' most fearsome cyborgs wasn't seen on-screen in Attack of the Clones, General Grievous was secretly present during the pivotal Battle of the Geonosis. Although he wouldn't make his public debut to the galaxy until the Battle of Hypori shortly after the dawn of the Clone Wars, a surprising yet canonical source reveals that Grievous was once Count Dooku's perfect secret weapon wielded against the Jedi Order from the very beginning of the Republic's war with the Confederacy of Independent Systems.
Manipulated and reshaped with cybernetic enhancements by Count Dooku, General Grievous was handpicked from his homeworld of Kalee to lead the Separatist droid forces. Rather than being motivated by the promise of power or an interest in the politics of the Clone Wars, Grievous' goal was brutally simple in that he wanted the rid the galaxy of all Jedi, his sworn enemies. Making his first public appearance as Supreme Martial Commander during the recently re-canonized Battle of Hypori, the debut of Grievous and resulting Jedi slaughter was the Republic's first major loss and was a huge blow to morale. However, Hypori wasn't the first time General Grievous killed Jedi in service to Count Dooku (and by extension Darth Sidious, the true orchestrator of the Clone Wars).
As revealed by 2016's Star Wars Helmet Collection #8, the issue's exploration and analysis of the droid general reveals that General Grievous was secretly involved in the Battle of Geonosis. Tasked by Count Dooku to protect the Separatist leaders as they made their escape, Geonosis was Grievous' first true test where he proved his sinister worth to Dooku, who had trained him in lightsaber combat. Positioned within the Geonosian catacombs below the arena and droid factories, Grievous ruthlessly slaughtered the unfortunate Jedi and clone troopers who ventured below, leaving none alive to reveal his existence.
Why General Grievous Was Count Dooku's Ultimate Secret Weapon
While it was only a matter of time before General Grievous would be revealed to the galaxy as a critical leader in the Separatist movement, it's clear that Count Dooku saw the value of keeping him in the shadows for as long as possible. Grievous' lethal Jedi-killing capabilities and the initial mystery of his existence proved to be devastating once Grievous was finally unleashed upon the galaxy, thus giving the CIS their first major victory. It proved that the galaxy's Jedi protectors were vulnerable, motivating more systems to join Dooku and the Separatists against the Republic.
While it would have been exciting to see General Grievous on-screen during Attack of the Clones, the fact that he was secretly present during the Battle of Geonosis is impressive in its own right. Killing in secret as Count Dooku's secret weapon makes Grievous even more sinister given his singular purpose of exterminating Jedi. As such, this somewhat hidden piece of canon serves to be a foundational reason for why General Grievous is one of Star Wars' greatest villains. He was a major threat before the Jedi Order even knew he existed.