Hythlodaeus's mouth stays open as he looks between the two versions of Hades. He'd expected himself to be reasonable enough to fully understand that the younger one is an illusion, and yet the real Hades's response makes him realize that he would never be able to raise a hand at the vision. It's too similar to someone too dear to him.

The illusion of Hades, meanwhile, purses its lips, then shoots another glare in Hythlodaeus's direction before looking back to the real Hades.

"You are placing your trust in someone who is incapable of holding it up. You would be better served saving yourself the disappointment and leaving him once you've found your exit."