Gix, Yawgmoth Praetor [Tarkir: Dragonstorm Commander]

Whenever a creature deals combat damage to one of your opponents, its controller may pay 1 life. If they do, they draw a card.
{4}{B}{B}{B}, Discard X cards: Exile the top X cards of target opponent's library. You can play lands and cast spells from among cards exiled this way without paying their mana costs.