Yes, you put Voldemort in the bottom of the villain stack, face up. So when the villain on top of him is revealed, he is revealed as well. He cannot be hit until all other villains are defeated. Also, all 3 villain spots are used.
No wonder we had trouble winning game 5! We thought Voldemort gets revealed at the start of the game. We seriously need to play this again since we weree playing it wrong this whole time