Relationship with the Empire: Visionary Opportunists
Joining the Rebellion: The Accidental Rebel

HK-91 is the prototype of a new line of assassination droids, based on ancient designs discovered by the Empire. Manufactured in secret on board the star destroyer Aspirant, HK's creators envisioned that his line would spread fear of the Empire across the galaxy by ruthlessly assassinating any opposition.

Once activated, HK-91 was given the task of defeating 10 of the best troopers aboard the Aspirant in a series of combat drills. Prior to the drills, the droid broke containment, hacked into the Aspirant's environmental controls, and vented all oxygen in the stormtrooper barracks.

Though he accomplished his mission, the Aspirant officers were less than pleased and unconvinced by HK's arguments that he is an assassination droid - not a battle droid. When he insisted that they were at fault due to designing an "idiotic" test, the project was scrapped entirely. All data was deleted, a cover story was created for the deaths, and HK was deactivated and jettisoned with the trash.

Luckily for the droid, Rebel agents aboard the Aspirant identified the usefulness of such a droid and included a homing beacon in the trash dump with him. The Rebel Alliance quickly recovered the droid, fitted it with a restraining bolt, and partially reprogrammed him to serve the Rebellion.

Quest: Vengeance

HK-91 greatly dislikes the empire, and not just because the Rebellion attempted to program him that way. Considering himself as the pinnacle of assassin droid technology, he views the Empire's discarding of him as a grave insult. One he intends to repay in kind.