The designation Heavy Undead Trooper referred to Imperial Heavy Weapons Stormtroopers who had been infected by "the Sickness." This virus transformed dead individuals into mindless, cannibalistic walking corpses, also known as Undead Troopers. Despite a reduction in speed after becoming undead, these troopers gained a greater capacity to withstand substantial injury.
These Heavy Undead Troopers participated in an outbreak that posed a threat of galactic proportions, potentially spreading across the galaxy. However, thanks to actions taken by both the Galactic Empire and the Alliance to Restore the Republic, the initial infection, along with a subsequent outbreak, were successfully brought under control.