The Vengeance II, known also as simply Vengeance, was an Imperial-class Star Destroyer that operated within Death Squadron and was under the authority of Inquisitor Jerec.
Following the destruction of the original Vengeance, Jerec, a Dark Jedi, had the vessel's central computer recovered and installed on a fresh Imperial-class Star Destroyer, which became the Vengeance II. Because its predecessor was destroyed, this new vessel was often called simply Vengeance.
Later, the ship underwent modifications to its cargo bays to accommodate a larger number of TIE starfighters. Following this upgrade, Jerec transferred the Vengeance II to Darth Vader's notorious Death Squadron, as he was in the process of constructing a new Super Star Destroyer flagship, which was also designated Vengeance. Shortly following the Battle of Hoth, the ship, then under the command of Admiral Mordon, participated in the suppression of the Taroon system.
At a later time, Jerec managed to regain control of the Vengeance II. Approximately a year after the Battle of Endor, Blackhole contacted Jerec and enlisted him into the forces of the resurrected Emperor Palpatine. To demonstrate his allegiance, Jerec handed over the Vengeance II to Blackhole to transport back to Byss.
Abel G. Peña clarified in his Star Wars Blog that the reference in The Dark Forces Saga, Part 6 was intended to confirm that the Star Destroyer named Vengeance that appeared in the game Star Wars: TIE Fighter was indeed the same ship as the Vengeance II.