Final Battle

You must control at least 15 creatures to cast this
spell from anywhere.
Untap all creatures and begin a special combat
phase: One at a time for each creature you
control that is not prevented from attacking due
to any spell or ability, choose an opponent or an
opponent's planeswalker for it to attack.
Opponents may declare blockers in response.
Any damage done to players during this special
combat phase is doubled.