NB4 was a porter droid with masculine programming who was employed by the Rodian bounty hunter Slyder while on the starship Star of Empire. During the year 1 BBY, NB4, while performing his duties as a serving droid for the Star, encountered Lieutenant Kyle Katarn, a recently established officer of the Galactic Empire. Believing him to be a person of interest, NB4 reported him to Slyder.
A little while later, NB4 was sent after the passenger Jan Ors, whom Slyder identified as a Rebel Alliance agent, and bugged her starship with a remote transmitter. NB4's espionage eventually revealed a relationship between Ors and Katarn that ended with the officer defecting from the Empire. Slyder used NB4's acquired data to report the rebels to Governor Dol Donar II, who subsequently hired Slyder to capture the rebels.
A porter droid with masculine programming, NB4 also assisted the Rodian bounty hunter Slyder who made his living onboard that ship for several years.
Although NB4 was largely unaware of Slyder's ultimate plans, his cooperation included the tracking down of individuals who ought to have a bounty on their head, after which Slyder would offer his services to capture them to whoever was most likely to buy—generally this ended up being the Galactic Empire.
During 1 BBY, NB4 and Slyder caught wind of several Rebel Alliance agents who were aboard the Star of Empire and notified Slyder who looked suspicious. Using hidden cameras, Slyder was able to identify them as Jan Ors, Rosco Ross, Ris Waller, and the protocol droid A-Cee. Meanwhile, as one of the many Star of Empire servant droids he welcomed the recent Imperial graduate Lieutenant Kyle Katarn, offered to take his bag and checked his , before leading him to quarters aboard the ship at what he called the "Starlight Deck."
The Imperial graduate Kyle Katarn became one of NB4 and Slyder's last targets together.
Having heard that the luxury ship's owners—the Haj family—had rebel sympathies, Katarn questioned NB4 on the matter of "sharing coordinates". The droid was initially confused by Katarn's use of a metaphor, but eventually admitted that he didn't know; his job was to brief Katarn on the layout and purpose of the ship. Something in Katarn caught the droid's interest and he notified Slyder that the young officer would be a potential target.
Katarn later left his bunk, and eventually ended up in the ship's Corellia Room, where he was spied by Slyder, and caught a glimpse of Ors and, having recognized her from an early mission of his, attempted to follow her. Slyder witnessed these events and through his suspicion had NB4 keep tabs on Ors. NB4 eventually found her in the Star of Empires hangar, where he noticed Ors struggling with the repairs she was making to her starship Truly Sorry. NB4 offered assistance, as the were unavailable, but Ors declined. Having nonetheless learned Ors' first name, NB4 left to rendezvous with Slyder, but not before placing a hidden transmitter on her ship. The transmitter recorded a conversation between Ors and Katarn, during which Katarn announced his intention to defect. With this new information in hand, Slyder then explained to NB4 what his lengthy tenure aboard the Star was all about.
Slyder thanked the droid for his assistance and competence, the latter of which NB4 claimed to only exist because of the years of experience he attained by being at the bounty hunter's side. Afterwards, Slyder left his cabin to meet with the Imperial governor Dol Donar II in order to sell his services to the Empire and catch the rebel agents. Slyder never returned, however, as he was killed aboard Dol Donar's yacht when it exploded just outside the Star of Empire while in pursuit of the Truly Sorry, thus ending NB4 and Slyder's long standing partnership.
Slyder, NB4's partner on the Star of Empire.
One of many service droids aboard the Star of Empire, NB4 was an auspicious spy that drew little attention to himself. Neither Katarn nor Ors were able to ascertain NB4's ulterior motives while in contact with him, and the droid was discreet enough to plant a transmitter on Ors' ship without her notice.
NB4 had a keen photoreceptor for interesting individuals, and successfully targeted Katarn as a valuable target. NB4's unassuming nature allowed him to get close to his targets and gain their trust, which in turn aided his role as an assisting porter droid. NB4 believed his abilities were to be attributed to Slyder's tutelage.
As a porter droid aboard a luxury liner, NB4 encountered various alien species during his work, and happened to be very knowledgeable about the Star of Empires crew and layout; he said that the cheap "Starlight Deck" is located at the very center of the ship's activities, meaning the engines. However when he was asked about the Haj political loyalties, he claimed ignorance, as something beyond his main programming, that is, operating the elevators. Katarn's use of the metaphorical term "share coordinates," which referred to two parties secretly working together, briefly confused the droid until Katarn explained the meaning. Pleased with having learned something new, NB4 attempted to use the same metaphor while speaking to Slyder, although the Rodian did not understand it. NB4 did not explain its meaning, however.
The character of NB4 was created for the audio drama based on the William C. Dietz novella Dark Forces: Soldier for the Empire. NB4 himself, however, was not originally featured in the novella—Slyder seemingly worked alone in the novella. Rather, NB4's purpose, as apparent from the majority of his dialogue, was to serve as a method of translating a portion of the novella's prose into spoken words in order to explain the backstory of certain events and characters.
Additionally, in the novel, Katarn's defection is recorded and transmitted by a -like microdroid; in the audio drama, it is revealed that NB4 ws responsible for bugging the Truly Sorry when he approached Ors.