B-2ON functions as a protocol droid assigned to the twins Am and Karre, dark side creations destined to command the remnants of the First Order and Sith Eternal. His jet-black metallic body and red visual sensors provide a stark contrast to C-3PO's gold appearance, signaling his allegiance. The droid's name itself encodes a subtle homage: shifting each character forward reveals "C-3PO."

Present since the twins' delivery to the Gemini-class Star Destroyer, B-2ON observed their development from the earliest stages. He demonstrates unwavering loyalty to Am, consistently addressing her as "Master Am" and providing advisory services. His demeanor blends the formal reserve typical of service droids with occasional emotional outbursts fueled by devotion to his masters. During preparations to activate the hypercannon, B-2ON voiced apprehension regarding the prototype dark armor's potential physical toll on the twins, concerns Am dismissed.

When Karre stole the kyber crystal power source crucial for the superweapon, B-2ON accompanied Am to confront him in the hangar bay. He expressed disappointment at Karre's betrayal and supported Am throughout the ensuing conflict, surviving an X-wing assault only through Am's Force protection. Following the twins' destructive lightsaber duel in space and the severing of the Star Destroyer, B-2ON located Am's unconscious body within the wreckage, retrieving her from the debris field. This action highlights his core function as Am's protector, maintained even amidst catastrophe.

His operational parameters prioritize strict protocol adherence and uninterrupted service, leading him to identify as their "humble servant" until functional termination. B-2ON's design and behavioral programming deliberately parallel C-3PO's mannerisms, including apprehensive tendencies and formal speech patterns, yet distinguish him through singular dedication to dark side operatives.