In the mirror universe, K'mdek was a Klingon warrior who lived during the 23rd century.
In 2282, he and Gejh accompanied General Kor to Cestus III to meet a Ferengi black marketeer named Lorp in order to obtain information regarding a top secret project being run by the Imperial Starfleet aboard the supposedly abandoned Regula 1 Space Laboratory at the edge of the Mutara Nebula. Lorp's payment was a complete set of holographic schematics of a cloaking device. However, after Kor reviewed the data, K'mdek and Gejh killed Lorp and his two henchmen using their disruptors. (TOS - Mirror Universe novel: The Sorrows of Empire)
- It is unknown if K'mdek has a counterpart in the primary universe.