Invasion of Karsus
(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 Invasion of Karsus enters the battlefield, it deals 3 damage to each creature and each planeswalker.
Refraction Elemental
Ward—Pay 2 life.
Whenever you cast a spell, Refraction Elemental deals 2 damage to each opponent.