Avenger NX-09, I.S.S.
A starship in the Mirror Universe, the Avenger was commanded by Admiral Black.
The Defiant, under the command of the Mirror Universe's Jonathan Archer, came to the Avenger's aid during a rebel attack. The Avenger joined the Defiant at warp, soon after Admiral Black boarded Archer's starship from the future.
After Archer killed Black with a hand phaser from the Defiant, the Avenger's crew joined the Defiant, with the Avenger presumably scuttled.