Gonti, Notorious Larcenist

Deathtouch Haste
When Gonti attacks, look at the top four cards
of target opponent's library, exile one of them face down, then put the rest on the bottom of that library in a random order. You may cast that card for as long as it remains exiled, and mana of any type can be spent to cast that spell. Then repeat this process if you have no cards in hand.