Sorry about my posting delay...I should be able to speed up now. 
The winged creature turns arounds at the sudden sound. He's slightly taller than you two are, you notice horns and a trident that the creature is carrying. If not for the red skin, he'd look...relatively human. On the dais behind him is some sort of sacrifice, but it's too dark and far away to tell what it is.
In a booming voice,
"So you are the ones here at Vecna's sufferance. You would do well to heed his wisdom in bringing you here...and avoid the denizens of the darkness. HE brought you here to warn you...there is more afoot than you can know. More than I am permitted to tell...if I even wished to. I have, however, been watching your progress. Most amusing."