Ragavan, Nimble Voidwalker

Shadow, Dash {1}{b/r}
Whenever Ragavan, Nimble Voidwalker deals
combat damage to a player, create a Treasure
token and exile the top card of that player's
library with a void counter on it.
{t}, Sacrifice a Treasure token: Choose an exiled
card an opponent owns with a void counter on it.
You may play it this turn without
paying its mana cost.