Dragonlord Caladra

Flying
Whenever another creature you control deals combat damage to a player, shuffle it into your library. If you do, look at the top three cards of your library. You may cast a spell from among them without paying its mana cost. Then shuffle your library.
"The Caladra are literally as consistent as their Dragonlord wants them to be."
- Taigam, Ojutai Monk