Originally posted by TBTabby:
Something’s wrong with this raid. If the damage counters are correct, we should’ve beaten Tyranthius by now, but his energy bar barely shows any damage.
Tyranthius raids start regenerating health once hp drops below 20%. Source: http://dotd.wikia.com/wiki/Lord_Tyranthius_(Raid)
For this reason, you have to finish him off fast once his health drops low.