'Harry Potter and the Deathly Hallows -- Part 2' posters: Go, McGonagall!
Voldemort someone who has no conscience, no remorse, and unwillingness to change in order to save himself. A true evil being.
Ralph Fiennes lookin amazing and flowy as Voldemort Ralph Fiennes as Lord Voldemort Harry Potter Deathly Hallows Movie
You may also choose to have a You-Know-Who drinking game going on throughout the party, in which there is a penalty (such as doing a shot) for saying "Voldemort" as opposed to "You-Know-Who" or "He-Who-Must-Not-Be-Named." I like to call this one "Whatsizface?" You have to warn your guests of this game in the beginning, so that designated drivers and those on diets will be exempt. You may choose to have those in the game to wear tags. At any rate, lay plenty of traps, such as "Voldemort for President" signs and things that will cause people to want to say his name.