In the mirror universe, Kryton was an Elasian male and the top lieutenant of Elaan, the Dohlman of Elas. Kryton was in love with Elaan and wished to marry her. He was furious when he heard of her plans to wed Hakil, Caliph of Troyius. This led him to betray Elaan to the Klingon Empire because of jealousy.
In 2268, the Terran Empire assigned the ISS Enterprise to transport Elaan to Troyius in order to prevent the Klingons from conquering their worlds and gaining access to their rich supplies of dilithium crystals. While aboard, Kryton attempted to sabotage the Enterprise but was caught before he could do so. After being severely beaten by Imperial Starfleet security, he was presented to Elaan, who told him that he was a "lowly soldier" who was "not permitted to love one such as [her]." Immediately thereafter, he was taken to the brig and executed on the orders of Captain Spock. (TOS - Mirror Universe novel: The Sorrows of Empire)