[@Raijinslayer] - Hmm.
How about, for now, we include the first bit of being cloaked in his corruption with the increased speed, and strength. And through developing his powers, he will eventually gain the ability to shape-shift his whole body and arms. Or, rather, he can shift one arm into a "temporary weapon" and then his whole body as he gets stronger. OR - he can shift into the stream of shadowy corruption to dodge and parry blows.

Take your pick. c: