HKB-3 droids were easily modified hunter-killer droids. They had square heads and were equipped with rapid-fire blasters. They relied on a Central Control Computer to coordinate their operation. This feature made them effective at tracking a target because they could easily coordinate with each other when sent out in groups. Individually they had poor targeting abilities, but in a group, if one droid honed in on a target, all droids in the patrol group could coordinate their fire on the same coordinates to maximize their effectiveness.
Prior to and during the Stark Hyperspace War, HKB-3s were favored by officials of the Trade Federation to serve as bodyguards and provide general sentry duties. It was during that conflict that Wookiee Jedi Master Tyvokka was killed after Trade Federation Minister Nute Gunray ordered his hunter-killer droid bodyguards to open fire on him.
By the time of Invasion of Naboo, they had largely been replaced by the highly-superior droideka. Though a rarer sight than the B-series battle droid, HKB-3 hunter-killer droids could still be seen during the Clone Wars, typically relegated to simple guard duties or patrolling remote planets.
- Star Wars: Republic 37: The Stark Hyperspace War, Part 2 (First appearance) (Appears in flashback(s))
- Scavenger's Guide to Droids (First identified as HKB-3 hunter-killer droid)