War's Desecration

Cast War's Desecration only if a player has been dealt combat damage this turn.
Destroy all creatures. Each player discards a card. War's Desecration deals 3 damage to each player and planeswalker.
Bloodshed gives way to more bloodshed, hatred creates more hatred, until all of the violence soaks into the land carving, rivers of blood. And no matter how many times it happens they never learn.