Haven't read all the adventures yet, but 152 "Essence of Evil" by Robert Schwalb has two apparently new monsters: black cysts and the (unique) essence of Shothragot, which reminds me a bit of an obyrith, which I guess is appropriate, since it's the herald or somesuch of Tharizdun.
I was reading Dragon or maybe Dungeon the other day and found an aspect of Mephistopheles that was an 18 CR. Then I had to leave and deal with Christmas and all that. Now I cant seem to find it. Can anyone help?