In the mirror universe, Number One was a Terran female who served in the Imperial Starfleet of the Terran Empire during the mid 23rd century. She was the first officer of the ISS Enterprise under the command of Captain Christopher Pike. By 2264, Number One had numerous conflicts with Spock and had him reprimanded, leading Spock to request that Commander James T. Kirk eliminate her and promote him to the position of first officer of the Enterprise once he took command. Kirk agreed to these terms, killing Number One with the Tantalus field. (TOS - Mirror Universe short story: "The Greater Good")