Garthanos
Arcadian Knight
Or, since it's D&D a magic horn that'll cave the roof in or something.
This could call for a group bluff check.
Craziest-seeming PC: "This it! I'm going to sound The Horn of Doom!"
Everyone else: "What? No! Wait! It's not worth it!!! OMG! Don't look at its face! We're all gonna die! Let's surrender instead? you'll accept our surrender, right? please. Stop him! He'll kill us all!"
And if they flub it, the baddies are all like "Uh-uh, we saw The Corbomite Maneuver in re-runs, too."
I think the original concept is for an actual superior enemy force too much humor can be endemic I suppose with Monty in the picture.
I think making sure insight and history checks are a known method to discover enemies that may be out your league could also help with player siding part of the McGuffin adventure.