A conversation with a Cornu

While you search (and loot) the temple, Ashfallen speaks grandly to the empty room. It's not clear if he's actually speaking to you specifically, or is just talking out loud, in love with the sound of his own brilliance.
"I am more than a little impressed. When the Grand Cornu received word that Gudmund had moved his temple 'behind the scenes' he was actually concerned. The kind of leverage that Rappan Athuk provides is restricted to a finite placement of fulcrums. Gudmund's was best from a purely mechanical perspective, although the subtleties of the physics of the divine are somewhat wasted on the black robes.
I was sent here, while the Grand Cornu went to order the army to march upon your nests. The timing could not be better, this device *pat pat* is less an engine, and more a potential difference generator; activating upon it's own release. Imagine this hand were drawing back a sling; until the hand lets go, the system has impetus but does not actually initiate. Shutting down Zehn's node was enough to leave a scar, and Gudmund's had somewhat more power. The backlash is enough that none will come to your aid as the Unrighteous March moves upon your dominion.
You still have time to catch the Grand Cornu before he escapes your grasp. He sent me to tell you about the army marching to your door in an attempt to force your hand, but by sending me here he has also opened up the only path by which you could reach him in time. Had he not sent me, you would have likely returned to the surface with no warning of your impending doom. Ah:
"We fear those slithered chances / Snake whisper'd threats / That blind us to the golden shouts / Of the calm man's reason"
...It works better in Infernal. Youre sure you wish to return to the surface? When you're ready, cast your teleport spell, but draw upon the device's remains isntead of your own reserves; it has enough power to take you all to safety. 
My time here is up. Should you survive, and when you are ready (as it is a perilous journey), follow the March back until you find my library. I will take you to observe the extent of your failure for yourselves. There is no concern for the passage of time; in about two minutes your defeat will be inevitable.
Now to go find the Grand Cornu and report Gudmund's defeat. Poor fellow, let it not be said that I did not do everything I could to save him. Come along you four, and try to squeeze the excess blood out of your robes. It would be highly immoral for me to leave you alone with these adventurers."
With the same deafening crunching noise, Ashfallen and the four acolytes teleport away.