I liked the Archomental artical, nearly perfect timing.
Last Saturday (before i had magazine) my players ended up at Ogremoch's palace. There to confront his steward, a earth elemental sea Drake, but not Ogremoch himself. They firmly resloved not to try and take "Big O" on, as they are afraid of the ramifications of the power vacum. They also doubt thier ability to do so (as 18th lvl charaters) I was using a pargagon advanced elder earth elemental, with spells as a 1/2 elemental tacked on. But it does not look like stats will be necessary.
Cyroax is also long time foe, although they have only delt with his worshipers (fitting neatly in with the descriptions of methods in the artical)
I was less than satisfied with my physical version of him, and will be using the artical instead should he manifest.
As concept beings, the powers in my world cannot be slain, but they can create very powerful Avatars, and the loss of which can really set them back. Several hundread years back Ebon Maw (hunger demon lord) took over a large part of 1 contient with an Avatar, which was eventually slain. He has not recoverd from this loss. This is well established history, and the PCs fear Cyroax manifesting similarly.
Unfortunatly the planar challanges were much to weak to use, but they may show up as flavor. Ice and Magma Monoliths have a good chance of showing up, depending on player actions.