Herald of Dreams and Nightmare

Whenever Herald of Dreams and Nightmare
enters the battlefield or attacks exile the top
card of each player's library, you may play
spells exiled this way without paying their
mana cost until the end of the turn. If a card is
cast this way lose life equal to half its mana value.
Evoke - {0}
Reform (Exile an Island or Swamp from your hand, return this card from the graveyard, or exile to the battlefield tapped.)