In the mirror universe, Lieutenant Sean DePaul was a Terran male who served in the Imperial Starfleet during the mid to late 23rd century. In 2267, he served as the helmsman/senior helm officer/security chief aboard the Terran Empire's flagship, the ISS Enterprise, under the command of Captain Spock, starting as an ensign during the M5 wargames exercise.
In 2270, he served in this capacity as the Enterprise returned to the San Francisco Fleet Yards for a planned bow to stern overhaul and refit following the ship's 25 years of active service. He would be succeeded as flight controller by Ensign Saavik, who reported aboard the Enterprise in 2277 after graduating from Starfleet Academy. (TOS - Mirror Universe novel: The Sorrows of Empire)