Guile, Lost from Within

Whenever a player casts a spell, or if a creature an opponent controls declares an attack, exile this card from your hand, graveyard, or battlefield.
You may cast Guile, Lost from Within from exile.
When Guile, Lost from Within enters the battlefield, draw a card and reveal it and all copies of it from your hand and library if it is a nonland card. If that card is Guile, Lost from Within, transform this card.