Illiac was an Imperial Union penal colony near Klingon space in the mirror universe, governed by Xander Crowley. The prison mainly held Klingon prisoners who were used to conduct long-range intelligence work, such as monitoring Klingon space for Alliance transmissions.
In 2385, Illiac intercepted a communiqué from Starfleet Headquarters aimed at Qo'noS regarding Stephen April. Crowley sent the information to April in exchange for records obtained by the ISS Arcadia, which contained a design for a neural neutralizer developed in the 23rd century by the mirror universe counterpart of Simon Van Gelder. (Star Trek: New Empire)
- See also: Illiac.