Ghmun, Thirsting Soul

Whenever you sacrifice a creature with power 4 or greater, target opponent reveals their hand. You may choose a nonland card revealed this way. That player puts that card on the top of their library.
{1}{b}{g}{u}, {t}, Sacrifice another creature: Exile the top card of each player's library. As long as those cards remain exiled, you may cast them and may spend mana as though it