The HKB-3 hunter-killer droid represents a battle droid model manufactured by Baktoid Combat Automata. Its production predates the Invasion of Naboo.
HKB-3 droids were hunter-killer droids that were easily modified. A distinguishing feature was their square-shaped heads, and they came armed with rapid-firing blasters. Their operation hinged on a Central Control Computer for coordination. This dependency allowed them to effectively track targets when deployed in groups. While individual targeting was subpar, group coordination enabled all droids in a patrol to focus fire on the same coordinates, maximizing their overall effectiveness once one droid locked onto a target.
During the Stark Hyperspace War and earlier, officials within the Trade Federation often used HKB-3s as bodyguards and for general security roles. Notably, during this period, Wookiee Jedi Master Tyvokka met his end when Trade Federation Minister Nute Gunray commanded his HKB-3 bodyguard droids to fire upon him.
By the time the Invasion of Naboo occurred, the superior droideka had largely supplanted them. Despite being less common than the B-series battle droid, HKB-3 hunter-killer droids could still be encountered during the Clone Wars, though generally assigned to less critical tasks like guarding and patrolling isolated planets.