Runs with a permanent SoS (Speed of Sound, a Mins/Skald/Bard RA, makes you run REALLY FAST) and will supposedly (I have not tested this) drop items in your bag to encumber you. So you can't catch him. Make sure the casters have an auto-face macro made
The term MOB definitely describes this guy This guy is a runner. He does not attack at all, but will sprint all around the corridors. I was able to land slam on him only a few times. The best thing to do is have your casters line up along the pathway it takes, to nuke em as he goes by and have all tanks stick to him. His pathing will cuase alot of problems due to going in to walls. He can be defeated, but not until he has made every tank stuck to him from running around