In the mirror universe, Gwarz was a bald Klingon soldier in the service of the Klingon-Cardassian Alliance who lived during the 24th century.

In 2371, he was assigned to Celtris III. Gwarz and Khone bullied Jean-Luc Picard after he returned from New T'Karath. After Picard left his runabout, the Stargazer, to meet with his patron Gul Madred, Khone and Gwarz boarded the ship. They severely beat Wesley, the boy who was watching over the Stargazer, and plundered, vandalized, and destroyed Picard's possessions, including the last surviving bottle of Château Picard. (TNG - Mirror Universe novella: The Worst of Both Worlds)

It is unknown whether or not Gwarz has a counterpart in the primary universe.
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