This horrifying creature is a Carrion Golem, created through the necromantic arts from the parts of many corpses. Once the party unlocks the front door he appears and patrols the outside of the mansion. He is very slow moving until he spies an intruder, whereupon death comes swiftly and surely. It is best to simply avoid him at all costs.
He only does Crushing Damage; so buff/debuff like crazy against that.
He walks slowly and can be kited for a bit, BUT once he's taken any damage he begins to run around from target to target. He will also walk very slow UNLESS he has line of sight from his current target. Once he has line of sight, he will close and attack quickly.