An incident involving undead stormtroopers took place on the planet Dandoran sometime after the Battle of Yavin. This incident was triggered by an outbreak at a clandestine Imperial research installation. At this facility, a bioweapon referred to as the Sickness was developed. Both the Alliance to Restore the Republic, the Empire's adversary, and the Empire itself, were attempting to devise a method to halt the proliferation of the undead troopers throughout the galaxy.
In the initial years of the Galactic Civil War, the Galactic Empire operated a covert research center on Dandoran's southern landmass, where they undertook bioweapons research. This facility was responsible for the creation of a viral infection widely known as the Sickness.
Between the Battle of Yavin and the Battle of Hoth, the project went disastrously wrong. The troops of the Empire stationed at the research center were infected with the Sickness, which killed them and subsequently transformed their bodies into mindless, flesh-eating creatures. A distress signal was transmitted, but when the Imperial command responded, the facility was no longer transmitting. As it became apparent that an army of Undead Troopers was spreading across Dandoran, the Imperial commanders attempted to conceal the situation, while the opposing Alliance to Restore the Republic tried to find the origin of the outbreak.