Ritual to End the World

Hexproof
At the beginning of your upkeep, you may
sacrifice a creature. If you do, take control of
target creature an opponent controls with mana
value 3 or less. Then, if you control at least three creatures owned by opponents, sacrifice Ritual to
End the World and create a legendary 30/30 colorless Eldrazi creature token named Emrakul
with indestructible, flying, haste, and "You
control all creatures on the battlefield. You
choose the targets for all spells and abilities."