The Warden

The Warden is the creature who was responsible for maintaining the Prison of the Gods, and now that they have escaped, the current theory is that he is now responsible for rounding them all up again. We're fairly sure he's currently being controlled by the Telarus faction, although we don't know any details.
The Warden is able to detect magic use, and kills anything which does so. From what we can tell, it seems to be immune to magic, or at least partially so.