Dorthe, Yawgmoth Praetor

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 may play
land cards and cast spells from among cards
exiled this way without paying their mana costs.
Unlimited control of Brian