In the mirror universe, the Khitomer Conference was a diplomatic conference held in 2293 by the major Alpha and Beta Quadrant powers - namely the Terran Empire, the Romulan Star Empire, the Klingon Empire, and the Cardassian Union on the planet Khitomer - a Klingon held world near the Klingon-Romulan border. (TOS - Mirror Universe novel: The Sorrows of Empire)