In the mirror universe, Regent Worf (played by Michael Dorn) was the leader of the Klingon-Cardassian Alliance. Following the loss of Terok Nor to the Terran Rebellion in 2372, Worf resolved to recapture the station personally. He captured Garak, the former first officer of Terok Nor and the only Alliance official to escape the station alive. Worf initially accused Garak of being responsible for the loss of the station, but Garak deftly shifted the blame onto his former commander, Intendant Kira Nerys. Regardless of the blame, however, Worf had Garak locked in a dog collar and chain until the station was recaptured.
When the Battle of Terok Nor ended with an Alliance defeat, Worf raged that he had been betrayed -- he believed there could be no other explanation for his loss. Garak took the opportunity to blame the Intendant for the rebels' victory. Worf agreed, and began plotting with Garak to capture the Intendant and obliterate the rebels. (DS9: "Shattered Mirror")
In 2375, Worf finally captured the Intendant, along with Zek, who had crossed over to the mirror universe to open a trade agreement between the two realities. At the Intendant's suggestion, the Regent offered to let Zek go in exchange for a cloaking device, a technology that the Alliance did not possess. However, Rom sabotaged the cloaking device so that it would disable all of the Regent's ship's primary systems. With his ship completely disabled, the Regent was captured by the rebel warship Defiant. (DS9: "The Emperor's New Cloak")