Giyu Tomiaka

Haste, Trample, Doublestrike, Firststrike
When Giyu Tomiaka becomes the target of a spell or attack, flip a coin. If the coin is heads, the spell or attack has no effect. If its tails, the spell or attack has full effect.
When Giyu Tomiaka deals combat damage to a player, that player exiles cards from the top of their library until they find a non-land permanent. You may cast any number of spells from among those cards without paying their mana cost.