In the mirror universe, Diego "Red" Reyes was a Terran officer of the Imperial Starfleet during the 23rd century. By the 2260s, he held the rank of commodore and command of Imperial Starbase 47 (Vanguard) in the Taurus Reach. Part of his head was mutilated, and his right eye was a red-lensed, polished steel cybernetic replacement.
With the discovery of the Taurus meta-genome by then-Commodore Matthew Decker of the ISS Constellation, Reyes was assigned to the Watchtower class starbase deployed in the Taurus Reach. He was given his orders by the Empress Hoshi Sato III herself when he was assigned to the Taurus Reach, granting him absolute control over the region in order to carry out his assigned mission to unlock the secrets of the mysterious Shedai; to that end, he held a Shedai known as "the Wanderer" within the Vault deep inside Vanguard Station. However, Reyes began cultivating alliances with the Orions in order to fortify his position and establish his own personal fiefdom within the Taurus Reach, oft assigning the scout vessel ISS Sagittarius to scout for routes that could be exploited by Orion smugglers and slavers. (VAN - Mirror Universe short story: "The Black Flag")
Given his mission and a deadline to fulfill it, Reyes had no tolerance for those who questioned his orders, as he demonstrated to the chief researcher, Dr. Carol Marcus, when he threatened to torture and kill her son David if she did not return to work. She had told him bluntly that the Shedai would not remain contained for long, and it had to be disposed of. Clark Terrell, captain of the Sagittarius and secretly opposed to Reyes' power-grab in the making, had compiled a file on Reyes and Operation Vanguard over the years, and in 2275 transmitted the information to Admiral Spock of the ISS Enterprise; Reyes retaliated by jamming the transmission and destroying the Sagittarius.
After receiving Terrell's partly-jammed transmission and seeing the potential danger in Vanguard, Spock determined that Reyes would have to be terminated. To that end, he looked to cultivate an ally among Reyes' command staff, believing that - since "men like Reyes inspire treachery", as he put it - there would be someone who would be willing to aid them. When the way was open, he would dispatch his covert agent, T'Prynn. (TOS - Mirror Universe novel: The Sorrows of Empire)
Two years later, Lieutenant Ming Xiong, Reyes' chief enforcer in the Vault and the ally Spock was able to find, helped extract Dr. Marcus and her research team from Vanguard. Shortly afterwards - likely at the instigation of T'Prynn - the captive Shedai Wanderer escaped from containment, killing Reyes and his entire crew, numbering some three thousand. Captain Zhao Sheng of the ISS Endeavour, another ally of Spock, claimed Reyes' rank and command of his fleet for himself, destroying the station and leaving the Taurus Reach in chaos. (VAN - Mirror Universe short story: "The Black Flag"; TOS - Mirror Universe novel: The Sorrows of Empire)