At Day's End

As an additional cost to play At Day's End, exile
an instant or sorcery card from your hand.
Players shuffle their hands into their libraries, then play a Magic subgame starting at
10 life, using their libraries as their decks. After the subgame ends, if you won, you may cast 3 copies of the exiled card without paying their
mana costs until end of turn. If you lost, you
lose the game.