The Heavy Undead Trooper was the name given to Imperial Heavy Weapons Stormtroopers that had succumbed to "the Sickness," a virus that turned dead beings into mindless, walking corpses known as Undead Troopers with cannibalistic urges. Although slower in its undead state, it had the improved ability to sustain significant damage.
Heavy Undead Troopers were part of an outbreak that threatened to spread across the galaxy, but due to efforts undertaken by the Galactic Empire and the Alliance to Restore the Republic, the initial contamination and the secondary outbreak were contained.