In the Galactic Civil War era, Magg was a male Human operative of the Corporate Sector Security Police, secretly orchestrating a vast slaving operation. He formed a partnership with Zlarb, an individual he had previously apprehended for illicit organ sales. Magg exploited his position within the Security Police to ensure the continued profitability of their enterprise for four years. However, in 2 BBY, a mission to Lur took a disastrous turn, resulting in Zlarb's demise at the hands of Han Solo, the pilot they had hired. In the days that followed, Magg offered assistance to Fiolla, the Assistant Auditor-General of the Corporate Sector, in her investigation of the slaving ring. Despite his efforts, Solo and Fiolla successfully exposed his true identity, leading to his imprisonment.
Magg, a male Human, served as an agent within the Security Police of the Corporate Sector Authority's, focusing on minor criminal activities within the Corporate Sector. In 6 BBY, Magg apprehended Zlarb, who was involved in a relatively small organ-trafficking scheme in the region. Instead of bringing Zlarb to justice, Magg recognized a potential for personal gain. Magg and Zlarb began discussing a potential business venture, with Magg leveraging his Security Police connections to maintain an advantage over law enforcement. They decided that a slaving ring would be the most financially rewarding option. As a gesture of good faith, Magg offered to defer his share of the profits until their new venture reached a certain level of success. Over the subsequent four years, Magg and Zlarb's slaving partnership flourished, evolving into a large organization with multiple ships and hired muscle. They also established a connection with House Glayyd, a powerful entity on Ammuud, paying them generously to facilitate the passage of their vessels through their shipping firm while overlooking their activities. Although this arrangement became vital to their operation, they eventually initiated secret negotiations with the rival Reesbon clan. In 2 BBY, Agmor Glayyd, the clan patriarch, discovered Magg and Zlarb's duplicity, prompting the slavers to poison him.
Although Magg typically delegated the more dangerous tasks to Zlarb and rarely participated in the runs himself, he provided crucial logistical and practical support. He served as an accountant and provided technical expertise, in addition to his cover work with the Security Police. By 2 BBY, both had amassed considerable wealth, and with the Galactic Empire increasing its efforts to suppress slaving, they decided that the time was approaching to exit the business. However, to ensure a comfortable retirement, Magg insisted on undertaking one final run. Up to that point, Magg and Zlarb's slaving operations had generally proceeded without incident. However, this final venture, a trip to the snowy world of Lur, proved to be significantly different. The slavers had hired Han Solo, a spacer from outside the region, as their pilot, without informing him that he would be transporting a cargo of Lurrian captives. Although they intended to simply force Solo to transport the slaves, Solo, who held a strong personal aversion to slavery, and his Wookiee companion Chewbacca turned the tables on the slavers, resulting in Zlarb's death.
Following the disastrous mission to Lur, Magg resumed his duties in the Security Police, where he once again had to work to keep law enforcement off his trail. When Magg discovered that Fiolla, a Lorrdian Assistant Auditor-General in the Security Police, had initiated an investigation into his organization, he deliberately approached her to monitor her progress, eventually becoming her personally selected assistant. The investigation led them to the planet Bonadan, where Magg and Zlarb were originally scheduled to meet after the Lur mission. Solo, seeking the 10,000 credits he had been promised for the run, traveled to Bonadan for the same reason. Fiolla instructed him to follow the Corellian and investigate his connections to the slaving ring. However, after attempting unsuccessfully to break into Solo's ship, the Millennium Falcon, Magg abandoned Fiolla and returned to his associates, planning to eliminate both her and Solo.
Magg and his fellow slavers launched their attack shortly thereafter, boarding the Lady of Mindor, a passenger liner carrying both Solo and Fiolla, who had since joined forces, to investigate the slaving ring's connections on Ammuud. After conducting a systematic search of the Lady of Mindor, Magg caught up with Solo and Fiolla as they attempted to escape in a lifeboat. Encumbered by an bulky armored spacesuit and with his blaster in a thick, military-style holster, Magg was unable to match Solo's quick draw and was killed with a single shot before the pair could escape. Magg and his men regrouped and followed them to Ammuud, arriving on the planet just as Solo and Fiolla had acquired the evidence needed to incriminate him and his associates. Magg attempted to intercept the fleeing Millennium Falcon but was instead apprehended by a Security Police Star Destroyer, which arrived in time to take him and the other slavers into custody.
Despite his employment as an agent of the Corporate Sector Authority's Security Police, Magg prioritized personal profit over justice and demonstrated extreme deceitfulness and lack of principles in his criminal activities. Magg was primarily focused on protecting himself and his business interests, utilizing a diverse skillset to achieve his goals. He was a proficient lockpicker and skilled with technology, and his undercover abilities were so advanced that he even assisted in an investigation of his own slaving ring without raising any suspicion.
Magg's first appearance was in Han Solo's Revenge, a novel authored by Brian Daley and published in 1979. In 1993, Mike Vilardi illustrated him in Han Solo and the Corporate Sector Sourcebook.