Originally Posted by Runestar
Remember that with death ward at-will, it should never enter combat without one active. Final cr, I would peg at 18-20? This one, I need some feedback.
I think the defining feature here is that its immolation isn't too large, and that means its going to be difficult to use it effectively as a full-round action if the party is wise to its antics. So as intimidating as it might or might not be defensively, once you know its trick, it isn't threatening at all offensively really.
Blink and Blur would actually make it sort of threatening defensively if it didn't lose them when it immolated (which it does). It should be noted it also has Polymorph, which means it could be a real jerk about sneaking up near the party and then dismissing it behind a rock or something and immolating itself.
I would err more towards the side of low CR (16-17 even? DC 22 Reflex half is sorta laughable for its main ability), since for this thing to accomplish anything the party really needs to be asleep at the wheel. They may not kill it but it isn't really a huge threat.