Plague of the Firstborn

Each player sacrifices the creature with the highest
converted mana cost. If there is a tie, that
player chooses.
Every firstborn son in Egypt will die, from
the firstborn son of Pharaoh, who sits on
the throne, to the firstborn son of the
female slave, who is at her hand mill,
and all the firstborn of the cattle as well.
Exodus 11:5