EVO troopers were specialized stormtroopers trained to operate in harsh environments, utilizing special armor and equipment.
The troopers wore a variant of stormtrooper armor equipped with life support systems and more insulation, to prevent toxic chemicals from the environments to penetrate their suits. For weapons, they usually wielded flèche launchers.
EVO troopers were stationed on several planets around 2 BBY, encountering the secret apprentice of Darth Vader, Galen Marek. Despite their efforts, the apprentice killed all of them and other Imperial troops he encountered. Later in 1 BBY, EVO troopers had skirmishes with the clone of the apprentice, and he also managed to eliminate the troopers.