I pulled him several times when we were camping the two named mobs pretty close to the zone in but a little north of there. My 53% bard slow landed about half the time. He is snareable but its not really necessary as he never runs. His normal run speed is not as fast as the Discordling Enchainers as I was easily able to stay ahead of him on a pull with my bard speed and no drum up. He hits normal hard for this zone but we never had any problem taking him down. His graphic has him holding a sword but he never dropped any sword any of the times we pulled him. Just normal stuff like black sapphires etc. I am certain that he is not undead as we easily ran by him with invis on. I am not certain about him being Summoned class spells sucecptable or nor.
The Huvul type creatures seem to have a much higher magic resist than the rest of the mobs in Proving Ground. I had a difficult time getting slow to land even after tashing them. Would usually have to give it a couple tries to get it to land. Even then it was mitigated.