Willard Decker (mirror)

Original Timeline
In the mirror universe, Willard Decker was a $𝜇$ commander in the Imperial Starfleet and the son of Grand Admiral $𝜇$ 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 during a planned bow-to-stern overhaul, taking over for Admiral $𝜇$. However, Spock's mother, $𝜇$ - 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 in 2271, Decker was demoted to first officer under Spock's command, taking over for $𝜇$, 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 $𝜇$. 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 $𝜇$ subordinates took out the assassins; Decker was then himself killed by Ensign $𝜇$ and Lieutenant $𝜇$. Decker's father sought vengeance against Spock for Will's death, but was himself killed shortly afterwards.

New Timeline
In the new timeline created by $𝜇$ when he traveled to the past to warn his younger self of $𝜇$ reforms, Decker served as First Officer on the after $𝜇$ assasinated Spock.