if you would pay life while your library has at least that many cards in it, exile that many cards from the top of your library instead.
+1: look at the top two cards of your library. exile one of them and put the other into your hand.
−2: create two 1/1 black nightmare creature tokens with “at the beginning of combat on your turn, if a card was put into exile this turn, put a +1/+1 counter on this creature.”
−7: target player exiles the top x cards of their library, where x is the total mana value of cards you own in exile.