Coulomb's Comments

Stone Form doesn't appear to function as the tooltip describes it.  There is a "Stone" animation which includes a stun effect but health is restored at approximately 2 to 2.5 times the tooltip value all in one shot.  No stun on the next turn.

I've been camping this rare for days now.  There are more spawn points than mentioned.  He will appear at a couple of locations in the front room; at either end of the "ramps", the alcove mentioned and also at the top of the spiral ramp deep inside the cave.  You can stand on the first set of ramps with mini-map at max range and see the rare icon spawn in all of those locations.