Gill Gut Abomination

Menace
Whenever Gill Gut Abomination attacks, look at
the top two cards of that players library. Exile one
face down and put the other on the bottom of its
owner's library.
Whenever Gill Gut Abomination deals combat
damage to a player, you may choose a card from
among cards exiled with it. Until end of turn,
you may cast the chosen card without paying
its mana cost.