User blog comment:Allgorhythm/Managing the Damage Cap/@comment-23878607-20150522055019

The Ur will fly off in a huff as long as the Arisen is out of line of sight. Therefore, ducking behind the wall in the Slab room, or ducking behind the Slab itself, will do.

This does not necessarily prevent him from taking a potshot at you via High Frigor or High Levin before he flounces off, though...