Y66 Division functioned as a ground-based assault force within the Separatist Droid Army of the Confederacy of Independent Systems during the period known as the Clone Wars.
The arsenal of Y66 Division consisted of various combat vehicles and droids, including Single Trooper Aerial Platforms, Persuader-class tank droids, OG-9 homing spider droids, and Octuptarra combat tri-droids. To enhance their operational effectiveness in battle, all units assigned to this division were equipped with advanced, self-aware programming.
During the Battle of Christophsis, B1-series battle droids, B2 super battle droids, and tri-droids belonging to the division formed a second wave of assault against the Republic's 501st Legion and 212th Attack Battalion, while tank droids performed reconnaissance duties. The tri-droids acted as mobile, heavy artillery, hindering the advance of the Republic's forces. Anakin Skywalker, a Jedi Commander, orchestrated a flanking maneuver against Y66 Division, accompanied by Captain Rex and a small clone troopers squad. This tactic proved successful, leading to the destruction of the tri-droids and enabling the troops under the command of Jedi General Obi-Wan Kenobi and Commander Cody to eliminate the remaining battle droids.