These are undead. At around 10%, the one I fought became enraged. They can hit pretty hard, I was getting hit for over 150, with my ac being 1081. Root wore off very quickly, they can be poisoned. Dropped a black sapphire.
One of these dropped the blade for me yesterday. Must be a very rare drop because I've hunted there several hours now and have only seen this once. I'm checking what quests that could be for but haven't found anything yet. Any information is appreciated..