Although it is not known when she came to work there EV-9D9 was a supervisor droid under the Baron Administrator, Lando Calrissian for Bespin, Cloud City. The droid kept a low profile while working there so she could pursue her ambitions unnoticed. EV-9D9 was just one of malfunctioning EV-series supervisor/interrogator droid abominations created by MerenData and was one of the few droids who escaped capture when the EV-series supervisor/interrogator droid was to be destroyed after owners of the droids found out their cruel nature. While at Cloud City EV-9D9 added to herself a third eye just next to her left eye, which could "see" the droid equivalent of pain, which manifested as jumbled, incoherent signals. She had a pain simulator and a sadomasochistic personality, which was caused by an accidentally installed MDF motivator, taking great pleasure in the pain of droids.
Because of the role she played in Cloud City and the sadistic ideas she possessed, EV-9D9 was able to torture and destroy a quarter of the droids in Cloud City, including most of the 12-series traffic control droids stationed there. However, she was accidentally discovered and quickly exposed by her subordinate Sarl Random and forced to flee. She partially damaged the generators that held the city afloat and set a ship to automatic pilot as a distraction as she stole the Iopene Princess, a large Mining Guild ship. Despite the fact that security gave chase, she escaped.
After spending a short time working at the GoCorp, EV-9D9 came to work for the equally awful Jabba Desilijic Tiure, and rose to the rank of droid supervisor quickly and ruthlessly, overseeing all Jabba's droids. She kept a laboratory deep in the bowels of Jabba's Palace, where she built grotesque droids from extra parts that existed only to feel pain. During her years spent there she added several upgrades to herself so that she could feel more of the droid equivalent of pleasure while watching the coolant from dismembered droids pour out of them. She also employed her droid assistant 8D8 to burn and torture helpless victims such as a GNK power droid and a "Two-Onebee"-like droid. She assigned jobs to C-3PO and R2-D2 when they arrived at the Palace in 4 ABY. However, she soon discovered that Lando Calrissian had infiltrated the palace and ensured that there would be good jobs for the droids by removing competitors. She reasoned that he had tracked her down and was using the droids to get revenge, however, this was untrue; Lando's presence was a coincidence.
Around the time of Jabba's death, she was tracked down by 12-4C-41, a Traffic Control droid from Cloud City. Forwun removed EV-9D9's limbs and let loose her grotesque droid creations to destroy her, but not before removing her third eye and pain simulator so she couldn't even relish the pain of her own destruction.