"Here lies a peasant child scarred by the heat of battle.
Fighting not for glory but because he just wanted to live,
His despairation led him to victory."
~ Carved on the ornate stone doors leading to the large tomb.
Historically, most tombs known to have grave goods in them were robbed soon after the dead person was laid to rest. So why has the tomb that your group of adventurers broken into not already suffered this fate?
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".