Just from what I can see, he looks to be using some kind of mask. Breathing apparatus or gas mask perhaps?
If you look at his left arm, he seems to have a tube connecting to something attached to him. Since he's probably a melee focused character, I would think that's how he can add elemental damage to his melee attacks.
It seems to be shaped much like a mutated bruiser, or lab rat.
In one of the quick scenes, he seemed to attack a bit stylishly, but then in the next, he seems reckless.
It looks like he's wearing pants, so that's good too..
The trailer says he will be revealed at PAX East, which is in just over a week. Needless to say, I'm very interested in this character, and I'll be looking forward to next week!
The full, good quality trailer can be viewed below.