[quote=VitaVitaAR]
@TheFake: Okay, I realized what the one thing that was still making me hesitant is.

My one remaining concern is that, since anyone who hears him cast his two biggest spells is affected, this means that if player characters hear them they have nothing they can really do but stumble around blindly.
[/quote]

That's one of the big limitations. The easy way around that is to simply deafen each of them while casting (so they don't hear him) and then let them hear again once the effect is in place.