Invasion of Tarkir // Defiant Thundermaw

Invasion of Tarkir

(As a Siege enters, choose an opponent to protect it. You and others can attack it. When it’s defeated, exile it, then cast it transformed.)
When this Siege enters, reveal any number of Dragon cards from your hand. When you do, this Siege deals X plus 2 damage to any other target, where X is the number of cards revealed this way. (X can be 0.)

Defiant Thundermaw

Flying, trample
Whenever a Dragon you control attacks, it deals 2 damage to any target.