2011-09-22 : If all three cards have a converted mana cost of 0, no damage will be dealt.

2011-09-22 : If the targeted permanent or player is an illegal target by the time the ability resolves, the entire ability won’t resolve. No cards will be put into your graveyard, and no damage will be dealt.

2011-09-22 : If you have two or fewer cards in your library when the ability resolves, all of them will be put into your graveyard. Heretic’s Punishment will still deal damage equal to the highest converted mana cost among those cards.

2011-09-22 : The converted mana cost of a double-faced card in your graveyard is the converted mana cost of the front face.