Dieben, a male Nalydian criminal, was a wanted man on his homeworld of Nalyd for a variety of offenses. Ania Solo considered him to be dim-witted and not very creative when it came to fabricating stories. By the year 138 ABY, Dieben found himself working for Darth Wredd, a renegade Sith who had abandoned the clandestine One Sith organization. During the Carreras Incident, which also occurred in 138 ABY, Dieben was assigned the duty of guarding Yalta Val, an Imperial Knight who was being held captive on the desolate, floating world of Mala. His responsibilities included providing sustenance to Val and serving as a messenger between Wredd and his prisoner. Meanwhile, Darth Wredd, his master, was masquerading as the real Yalta Val and overseeing the construction of the Carreras G51 communications array.
When Darth Wredd utilized the Carreras communications array to disseminate his manifesto across the wider galaxy and make an attempt on Yalta Val's life, Dieben was present. Following the collision between the Carreras communications array and the planet Mala, Dieben made his escape in an escape pod. However, he was apprehended by Carreras security personnel in the Surd Nebula. Subsequently, he was extradited back to his homeworld of Nalyd to be held accountable for his transgressions. Given the magnitude of his crimes, Dieben received a death sentence to be carried out by a firing squad. While on their mission to track down Darth Wredd, Ania Solo, a junk dealer, and Jao Assam, an Imperial Knight, rescued Dieben from his execution with the intention of interrogating him about Wredd's location. During this interrogation, Dieben met his end when he was impaled by a sharp plant. Despite his demise, Ania and Jao later discovered, through his captors, that he had plans to meet with some "powerful friends" on Dac. This turned out to be a slaving operation managed by Darth Luft, another rogue Sith, and his pirate accomplices.
Dieben, a Nalydian criminal, made his home on the planet Nalyd, a world characterized by its rocky terrain and towering rock formations. During his time on Nalyd, he was known to have committed various crimes, including the assassination of a government minister, the assault of a law enforcement officer, and the sabotage of a public transportation system, resulting in ten fatalities. Due to the severity of his criminal activities, Dieben was facing capital punishment. However, he managed to evade justice by fleeing the planet. By the year 138 ABY, Dieben had entered the service of Darth Wredd, a rogue Sith who had murdered his master and departed from the One Sith order. Darth Wredd also abducted and impersonated the Imperial Knight Yalta Val, who had been dispatched on a mission to oversee the final phases of the construction of the Carreras G51 communications array.
Yalta Val was held prisoner at Darth Wredd's base, situated on the floating planet of Mala. Dieben was assigned the responsibility of guarding and providing sustenance to the imprisoned Imperial Knight. Val was compelled to wear Darth Wredd's former apprenticeship helmet and had his hands restrained. On one occasion, Dieben presented the captive Knight with an unappetizing green soup, placing the bowl on the floor for the Knight to consume. Approximately a week later, Darth Wredd contacted Yalta Val, extending an invitation to join his new Sith order, which would be grounded in the Rule of Two. Sensing Val's unease, Wredd encouraged his captive to embrace the dark side of the Force, as he himself had done. During this exchange, Dieben operated the holographic projector.
Having gained control of the Carreras communications array, Darth Wredd returned to his base, from where he could now remotely manage the station. Under Wredd's instructions, Dieben removed Yalta Val's helmet and escorted the captive Knight into a chamber where the rogue Sith delivered a broadcast to the galaxy. In his address, Darth Wredd derided the "weakness" of the Galactic Federation Triumvirate and attempted to assassinate the captive Yalta Val. However, his efforts were thwarted by Ania Solo, a junk dealer, who successfully liberated Yalta Val. Amidst the ensuing conflict, Dieben managed to escape in an escape pod before the Carreras communications array collided with the planet Mala. He had intended to rendezvous with some "powerful friends" on Dac—specifically, the rogue Sith Darth Luft and his pirate cohorts, who had established a slaving operation within the Mon Calamari Orbital Shipyards. Luft and his pirates were coercing Mon Calamari and Quarren refugees into constructing a pirate fleet.
Later, Dieben's escape pod was discovered in the Surd Nebula by unidentified security forces. He was promptly identified as a wanted fugitive and was extradited to his homeworld of Nalyd to face the consequences of his criminal actions. As a form of retribution, Dieben was sentenced to execution by firing squad in a public arena. While pursuing Darth Wredd, the rogue Sith, the Imperial Knight Jao Assam and Ania tracked him down to Nalyd with the hope of uncovering a lead on Wredd. Unable to persuade the Nalydian authorities to postpone the execution, Ania and Jao "rescued" Dieben and plunged down a steep cliff. Distrustful of his "rescuers," Dieben retaliated, biting Ania's hand, causing her to drop him to the ground. Dieben was impaled on a sharp, spiky plant, resulting in fatal injuries. Ania and Jao questioned him about whether he was planning to meet with Darth Wredd, but even in his final moments, he refused to divulge any information.
After returning Dieben's body to the Nalydian authorities, Ania and Jao learned that Dieben had been planning to meet with unspecified "powerful friends" in the Calamari system. Believing that this was their sole lead to Darth Wredd, Ania and Jao journeyed to Dac, only to discover that Darth Luft and his pirate associates had established a slaving operation in the lawless system. Jao succeeded in eliminating Darth Luft, while a Galactic Federation Triumvirate fleet liberated the Mon Calamari and Quarren slaves and apprehended the pirates. However, Jao and Ania later realized that their trip to Dac was a diversion orchestrated by Darth Wredd to achieve his objective of dismantling the One Sith and reinstating the Rule of Two.
As a wanted fugitive and murderer, Dieben was notorious for being unethical and disreputable. According to Ania Solo, he possessed limited intelligence and was incapable of deception. He displayed a lack of concern for his prisoner, Yalta Val, who was forced to consume a revolting meal while wearing a helmet and with his hands bound. He harbored distrust towards other sentient beings, as evidenced by his attack on Ania Solo during a rescue attempt. Ultimately, this action led to his demise. Even in his final moments, he remained defiant and uncooperative, taking his secrets with him to the grave.
Dieben made his debut as a minor antagonist in the comic series Star Wars: Legacy Volume 2 by Corinna Bechko and Gabriel Hardman, which is a part of the Star Wars Legends continuity. In the initial story arc, Star Wars: Legacy: Prisoner of the Floating World, Dieben's character was illustrated by Gabriel Hardman and colored by Rachelle Rosenberg. For the subsequent story arc, Star Wars: Legacy: Outcasts of the Broken Ring, he was drawn by Brian Albert Thies.