Invasion of Karsus // Refraction Elemental

(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, it deals 3 damage to each creature and each planeswalker.

Ward—Pay 2 life.

Whenever you cast a spell, this creature deals 2 damage to each opponent.