In the mirror universe, Dorrek, son of M'Raq was a Klingon male in the service of the Klingon-Cardassian Alliance during the 24th century. He was the younger brother of Klag. Their father M'Raq had died by 2372.
In 2372, he held the rank of commander and served as first officer of the IKS Slivin. He and his brother had a bet regarding which of them would be the first son of M'Raq to be promoted to captain and be placed in command of a warship. Klag ultimately won the bet, having been placed in command of the IKS Gorkon by Regent Worf. Consequently, Klag sent him a message telling him that he would have to buy Klag a bottle of bloodwine when they next met. (KE - Mirror Universe short story: "Family Matters")