Celaena Sardothian

Deathtouch, Unblockable
Whenever Celaena Sardothian deals damage to a player exile that many cards from the top of that player's library, for the remainder of the game you may you may cast any creature spells exiled this way. You may spend mana as if it was mana of any colour to cast those spells
Any encounter with the king's champion will usually end badly...
for you.