You don't have to reveal the cards in the face-down pile, no matter which zone they're put into. Resist the urge to gloat at the heroes if their decision serves your master plan.

You choose one opponent to make the final choice of which pile is put into your hand, but all players may discuss and advise this choice.

The split doesn't have to be even. The piles can be split with a single card in one pile and three cards in another. A pile can even have zero cards in it—in this case, an opponent chooses whether to put all the cards into your hand or into your library.