From Halopedia, the Halo wiki
Unggoy Bodyguards are Unggoy units faced by Spartan-IVs in Warzone simulations. They are outfitted with white Unggoy Heavy armor and possess weapons such as the Type-58 fuel rod cannon, Type-56D Needler, and T-54D Void's Tears. They are the only Grunt unit to have a personal energy shield, making them the hardest regular Grunt to kill. They appear when a Covenant boss, such as a Sangheili Pathfinder or a Goblin, is on the map.
List of appearances