“...And you, Human, must follow our words, lest we summon up every curse that lies buried beneath these sands and pour them upon you and your children, and their children, and in turn their children, for so many generations that your blood will surely never survive.”
A powerful wizard that the PCs encounter is completely silent. He does not speak and cannot be heard as he moves. Even his spells are silent, but his magic is just as potent.
He has a tendency to summon invisible chairs, place foes in invisible boxes of force, and other "mime tricks".