Escape Plan JGT-HB-4 was a backup evacuation strategy put into effect by Cylo, who had betrayed the Imperial cause and become a traitor. Following the conclusion of the War on Shu-Torun, Darth Vader discovered Cylo's whale fleet within the Crushank Nebulae while aboard the Imperial I-class Star Destroyer known as the Devastator. Upon seeing the Imperial ship, Cylo instructed Morit Astarte to begin Escape Plan JGT-HB, but then changed the directive to Escape Plan JGT-HB-4.
The initial appearance of Escape Plan JGT-HB-4 was in Darth Vader (2015) 21, a comic book from 2016 authored by Kieron Gillen.