[cyberdemon]

so he does have a face behind the armor.

Spoiler for speculation on spoilers for 4.3:

I'm positive Shadowhunter is in fact Gaius Van Baelsar. The white mask on his waist was the mask on Gaius's helmet previously. He was probably used as the body of Elidibus, which is what saved him from the explosion, up until the end of 4.0 when Elidibus discarded it in favor of Zenos's body. Having been betrayed by the Ascians and controlled by one, he took up hunting them down as his revenge.