A Massive Skin Thief
A massive Skin Thief, ogre sized. Able to use magic, including showing the ability to warp healing magics, and can wear multiple skins. Escaped by flying away on a pair of wings hidden underneath a skin. Accused you of working with “The One That Brings Pain”.
According to Pimply, Nurgle apparently felt the compulsion the Skin Thieves experienced stronger than all the others, and served as an organizing force. Nurgle has confirmed that he is the ‘highest’ of the Skin Thieves, and was respected because of this. You have speculated that this closer connection to whatever force is behind the compulsion is why he is different than most of the other Skin Thieves. You have not ruled out some other explanation, however, as The Builder (who has apparently been hired by the King to eliminate the Skin Thieves) has indicated that they are evolving in response to experience and outside stimulation.
You have run across him a number of times, including in the Slag, deep in the Underbelly, where he blocked your escape, but otherwise only watched as his minions futilely attacked you.
He has proven to be surprisingly reasonable this last time, allowing the Necromancers to take the unconscious Annalisse in hopes that they can remove the Builder’s taint from her soul. He told the party that if she was taken out of sight he would be compelled to rescue her. His leniency has caused a schism in the Skin Thieves.
He has spoken at some length about his people. According to him, there is a compulsion to rescue Annalisse. Some of the Skin Thieves have been unable to deal with this compulsion and his order to let the Necromancers keep her for now, and this has driven them mad. He states that eventually all will give in, but it is his hope Annalisse can be freed of the Builder’s soul before they succumb. He has made it obvious he intends to reclaim her by force, if required.