In the mirror universe, Gul Madred was a senior Cardassian officer in the service of the Klingon-Cardassian Alliance during the late 24th century. In 2371, he was the governor of Celtris III. He had a daughter named Jil Orra, with whom he had a very close relationship.
Madred was an enthusiastic amateur archaeologist who served as the patron of the Terran archaeologist for hire Jean-Luc Picard. He provided Picard with a vessel which the Terran christened the Stargazer. While in Madred's employ, Picard procured two of the three fragments of the Stone of Gol, a Vulcan psionic weapon, which was created prior to the Time of Awakening in the 4th century. Although Madred regarded himself on an expert on such matters, Picard found his knowledge to be sorely lacking. For instance, he erroneously believed that the Time of Awakening had occurred 4,000 years earlier. However, Picard considered it unwise to correct his patron.
At the behest of his superiors in the Alliance, Madred engineered a plan to lure Terran Rebellion operatives to Celtris III by fabricating bursts of theta-band subspace emissions emanating from beneath the planet's surface. Such emissions typically indicate that a metagenic weapon is in operation. The Rebellion sent Vash, Selar and Bagro to Celtris III to investigate these emissions. Although Vash managed to escape the planet and Selar seemingly faked her own death, Bagro was captured alive. Under torture, he told Madred that he had helped Vash smuggle an elderly Terran scientist named Noonien Soong off Celtris III and that Soong was travelling aboard the Stargazer. Madred then realised that Picard had betrayed him by joining the rebellion.
Several weeks later, Madred, who had a Galor-class class warship called the Hebitia at his disposal, was able to track Picard down to the Iconian homeworld which was located in the Romulan Neutral Zone. At the time of the Hebitia's arrival, the Stargazer was aboard to be boarded by the crew of the Romulan D'deridex-class warbird Gath'thong. However, as the Hebitia was equipped with a Klingon cloaking device, it was able to catch the Gath'thong unawares and destroyed the Romulan vessel with all hands. Picard, who had recently encountered the Borg aboard a diamond shaped vessel, attempted to warn Madred of the threat that the cybernetic race posed to the entire Alpha Quadrant. For his part, Madred dismissed the Borg as a archaeological myth and refused to believe him. Using the Br'er Rabbit approach, Picard further advised him to destroy the Iconian probe which was launched from the surface of the planet. As Picard had hoped, Madred took no action, believing it to be a transparent ruse on the part of the Terran Rebellion. Consequently, the Hebitia suffered a total systems failure due to the effects of the probe and was soon destroyed. Picard later used the probe to destroy the Borg diamond before it could assimilate the Klingon homeworld Qo'noS. (TNG - Mirror Universe novel: The Worst of Both Worlds)