In the mirror universe, Willard Decker was a Terran commander in the Imperial Starfleet and the son of Grand Admiral Matthew Decker who served during the 23rd century. He had an irrational fear of transporters, worrying that every time he was beamed somewhere, he was actually killed and replaced by a copy, unaware of the change.
In 2270, Decker was assigned as captain of the ISS Enterprise during a planned bow-to-stern overhaul, taking over for Admiral Spock. However, Spock's mother, Amanda Grayson - part of a wealthy and powerful family with connections to the Sato Dynasty - pulled some strings to ensure Spock would resume command of the Enterprise. Upon the completion of Enterprise's refit, Decker was demoted to first officer under Spock's command, taking over for Montgomery Scott, who resumed his duties as chief engineer. Discipline aboard the ship improved substantially under Decker's supervision. Still, he was often ignored by his commanding officer, to the point of being left out of tactical planning or diplomatic efforts, something he attributed to Spock's distrust of his father.
In 2277, he was involved in a plot orchestrated by his father to kill Spock on Deneva. Several assassins were hidden in a facility where Spock was instructed to attend a conference of the Admiralty. Spock, however, suspected a trap, and instructed Decker to attend the "conference" with him. Decker watched as Spock and his Vulcan subordinates took out the assassins; Decker was then himself killed by Ensign Saavik and Lieutenant Xon. Decker's father sought vengeance against Spock for Will's death, but was himself killed shortly afterwards. (TOS - Mirror Universe novel: The Sorrows of Empire)
In one permutation of the mirror universe, Decker was an officer serving aboard ISS Enterprise in the 2260s. James T. Kirk decided Decker had played a part in allowing the ship to be infiltrated by four imposters, and had him hanged in 2267, outside Starfleet Command Headquarters, alongside Leonard McCoy, Montgomery Scott, Janice Rand, Jabilo M'Benga, David Garrovick and Marlena Moreau. (TOS novel: Dark Victory)
|ISS Enterprise (NCC-1701) personnel|
|Robert April • Phillip Boyce • Christine Chapel • Pavel Chekov • J. Mia Colt • Robert D'Amato • Willard Decker • Michael DeSalle • Fein • Finney • Karl Franz • Gaffney • David Garrovick • Hadley • Idelson • Ilia • James T. Kirk • Winston Kyle • Roger Lemli • Jabilo M'Benga • Leonard McCoy • Marla McGivers • Marlena Moreau • Number One • Carolyn Palamas • Elizabeth Palmer • Christopher Pike • Janice Rand • Kevin Riley • Saavik • Montgomery Scott • Elizabeth Sherwood • Solok • Spock • Stang • Hikaru Sulu • Nyota Uhura • Xon • unnamed ISS Enterprise personnel|