Wong, Vigilant Archmage

Defender
Whenever a another nonlegendary, nontoken
creature you control attacks, you may put
the top card of your library into exile,
until end of turn, you may play that card by
paying {w}{u}{r} instead of its mana cost.
Whenever you cast a non-creature spell, Wong, Vigilant Archmage loses defender and gains
first strike until end of turn.