He is snarable, does summon. Could not cure the "vicious wound" with purified blood, RGC, corruption cures, or RC. It hit over and over on the pally we had tanking, so a little extra healing was required.
Can spawn from any of the 5 golem locations. Of the 5 or so times I've killed him I have only seen one armor essence, one Tempered Crystal Knuckles, a couple of the pendants, and one of the type-3 versions of the pendant.
Just know whoever pulls him will get hit with "Vicious Wound" and take about 2400 damage a tick as they come back to camp.....from then on, whoever has aggro will be the only one to get hit with it.

Distorted Medial Luminessence
Pendant of Chromatic Crystal
Pendant of Di-Chromatic Crystal
Tempered Crystal Knuckles