I would dub these guys Sentinels. Or Centurions. I imagine that they march into place on the high ground to keep watch over the surrounding area. Perhaps, once in position, the legs lock into a vertical tower. If they come under attack from something that could conceivably penetrate their thick armor, they just remain mobile. Plodding across the landscape to keep fire on the enemy, while avoiding damage by presenting a moving target instead of a stationary one.