Ad Nauseam

Instant

Reveal the top card of your library and put that card into your hand. You lose life equal to its mana value. You may repeat this process any number of times.

「一部のエリアは書籍を保存するため立入禁止。それ以外は生徒を保護するため立入禁止。」 ――大図書棟の古文書保管人、イサボウ