Protoguards were one of the four basic classes of Nefarious troopers, serving as the minions of Dr. Nefarious and Lord Vorselon. They were related to Splitterbots, Arc Strikers, and Cyclobombers. Like its cousins, they had an oval shaped, green, mechanical "brain" that was connected to the top of its red body, which was almost completely covered by one giant robotic eye.
The Protoguards usually stayed at a distance away from Ratchet and attacked him by firing lasers from their twin guns that were connected to their arms. They would also melee him if he came too close.
After Ratchet arrived on Vorselon's Warship in order to save Alister Azimuth, the robotic troopers became stronger, taking more hits to destroy them and were blue with silver armor instead of red and orange.