0-0-0 (or Triple Zero) is a protocol droid specializing in etiquette, customs, translation, and torture. Mostly torture.
The Triple-Zero Protocol Personality Matrix was created, tested, and promptly quarantined as far too dangerous ever to place in a droid body centuries prior to the rise of the Galactic Empire. It was retrieved and activated by the amoral archaeologist Dr. Aphra at the behest of Darth Vader, who became the droid’s new masters. The reborn 0-0-0 instantly returned to his old ways of genteely greeting organics before promptly exsanguinating them.
Along with his counterpart, the missile-toting astromech known as BT-1, Triple Zero continued to roam the galaxy with Dr. Aphra, sowing death and destruction in his polite, British-accented wake.