(coexisting on another dimensional plane)
Admiral Black was a high-ranking member of Starfleet in the mid-22nd century. In that capacity, Black forced Maximilian Forrest, captain of the ISS Enterprise, to replace his own chief engineer with Commander Charles Tucker. (ENT: "In a Mirror, Darkly")
Black was aboard the ISS Avenger in 2155 when it came under attack by rebel forces. After Avenger's captain was killed, Black took command and attempted to combat the rebel vessels. Black and the rest of the Avenger crew were saved, however, by the intervention of Commander Jonathan Archer aboard the USS Defiant, a starship from the future with extremely advanced technology.
After accepting Archer's invitation to board the Defiant, Black congratulated him on the achievement of appropriating such a powerful vessel for the Empire, and informed him that he intended to recommend he be given a command of his own. Archer subsequently requested a battlefield commission of captain of the Defiant, to which Black responded that the Defiant would be returned to Earth where its tactical systems could be analyzed. In response to Black's refusal to grant him command of the Defiant, Archer killed Black by vaporizing him with a hand phaser. (ENT: "In a Mirror, Darkly, Part II")