Klingon Alliance battle cruisers

In the mirror universe, four Klingon Alliance D7 battle cruisers, under the command of Lord Skarl, pursued the ISS Enterprise after destroying another Constitution-class vessel. The Enterprise turned loose a modified version of the Tantalus Field of the vessel, obliterating most of their forces. Skarl retreated, intent on finding new allies to help him defend Klingons from the Terran threat.