In 2269, he was the Governor of Elba II. In that year, he conspired with Grand Admiral Garth of Izar to assassinate Admiral Spock. To that end, they invited Spock to a lavish ceremony in his honour held in the Elba II governor's mansion. Although Cory missed the ceremony itself, he introduced himself to Spock and his wife Commander Marlena Moreau at the subsequent reception. After sympathising with the admiral over the recent death of the ISS Enterprise's chief medical officer Leonard McCoy from xenopolycythemia, he offered Spock and Marlena the use of his suite for the night.
However, Spock was aware of Garth and Cory's plot to assassinate him and used the Tantalus field to eliminate both Garth and his "prime consort" Marta. It is unclear if the same fate befell Cory. (TOS - Mirror Universe novel: The Sorrows of Empire)