Emperias, the Scorching Wish

Flying, Vigilance
Whenever a dragon you control attacks, exile
the top card of defending player's library. For as
long as you control Emperias, you may cast that
card and use mana of any color to cast it.
The people of Tarkir heard legends of a dragon
above the sky. Those who have lived to see it find
knowledge beyond their years or a quick death.