[Coldsaturn]

OK other theory: The first thing that comes to mind looking at that is blood, and Zayne is known to use his evol to slow down bleeding/infection etc. By doing that he might have overexerted himself again, thus triggering the black frost on his hand again.

But if I remember correctly there was this moment where it seemed like he was pulling a globe of ice/frost from her body and reabsorbing it into his hand? And then his hand went black? I need to look at that chapter again, I can't remember exactly now