So which Desert of Desolation Monster isn't in the Monster Manual I?

[Drammattex]

#1 possibility: Angel of Vengeance. The whole "why waste page space with something the PC's aren't supposed to FIGHT!"

I'm guessing that with the greying of alignment, there might not be anything in the monster manual that you are not supposed to fight. I think the Capricious Copper Dragon is a testament to that.

Angels may be the adversaries of devils, but who's to say the devils weren't right?
;-)