K-OB7, also referred to as Kayo, was a droid who began serving the Bimm Sith adept Toki Tollivar soon after the conclusion of the Great Sith War. Kayo "assisted" Tollivar by concealing the corpses of those he had strangled. Ultimately, Kayo and Tollivar found themselves marooned on the luxurious yacht Chancellor Fillorean until Zayne Carrick and the crew of the Hot Prospect located and salvaged the abandoned vessel.
Sometime before, during, or shortly after the Great Sith War, K-OB7 was assembled within a Kellenech facility on Rendili. Notably, this was the same manufacturing plant that produced the LB-series bulk-loading droid T1-LB. A short time after the Great Sith War concluded, Kayo entered the service of Toki Tollivar, a Sith adept. Initially, Kayo perceived Tollivar as a kind and agreeable individual, until one evening when he discovered one of Tollivar's associates deceased. Horrified, Kayo's master was assisted by Kayo in concealing the body. Over the following year, an increasing number of corpses materialized wherever Kayo and his master traveled. Kayo remained puzzled as to how such a diminutive being as Tollivar could strangle so many individuals.
Eventually, authorities from Corellian began pursuing Tollivar under his most recent alias, Kelven Garnatrope. Consequently, Tollivar booked passage aboard the Chancellor Fillorean, a ship catering to the wealthiest clientele. However, the killings resumed, and before long, all passengers and crew members aboard the Fillorean were deceased, with the exception of K-OB7 and his master. Lacking the expertise to pilot a ship like the Fillorean, Tollivar inadvertently stranded both himself and Kayo aboard the vessel. Eventually, the Hot Prospect and its crew—Zayne Carrick, Rohlan Dyre, Jarael and Slyssk, discovered the adrift vessel. While the crew investigated, Kayo launched an attack on Zayne, seeking to protect his master. However, Kayo proved no match for Zayne and Rohlan, and an innocent-seeming Tollivar begged them not to harm Kayo. Tollivar then presented his account of the events aboard the Fillorean to Zayne, prompting everyone to commence an investigation. Kayo encountered T1-LB in the Hot Prospect's cargo hold and initiated a conversation. He succeeded in prompting Elbee to speak once more and even contribute to the handling of the corpses aboard the Fillorean.
Rohlan Dyre soon deduced that the passengers and crew of the Fillorean had not succumbed to asphyxiation, but rather had been strangled. Rohlan implicated K-OB7 in the deaths of the passengers and crew of the Fillorean. After discovering Slyssk nearly strangled to death, Zayne also suspected Kayo of involvement in the deaths and severed Kayo's arms with his lightsaber. Elbee attempted to defend Kayo against Zayne and Rohlan, asserting that Kayo was programmed solely for "helping." Kayo then disclosed his and Tollivar's history to Zayne and Rohlan, arousing enough suspicion to pursue Tollivar. Tollivar revealed himself as the perpetrator behind all the killings and attempted to strangle Jarael. Zayne and Tollivar engaged in a duel until Kayo intervened. Kayo attempted to subdue his master by restraining him from behind, maintaining his grip even as the Sith attempted to break free using Force Lightning. Rohlan seized the opportunity to shoot both Kayo and Tollivar with his blaster, resulting in Tollivar's death and Kayo's destruction.
John Jackson Miller mentioned that the Death Star droid action figure, which he described as "the creepiest looking thing in the whole Kenner line," served as the inspiration for K-OB7's bug-eyed appearance.