Cast Worldfire by paying ({6} magic symbol) ({R} magic symbol) ({R} magic symbol) ({R} magic symbol) , exiling all permanents, all cards in all hands and graveyards, and setting each player's life total to one.
Outpost Siege triggers for each creature you had leave the battlefield this way.
Resolve the first Outpost Siege trigger, dealing 1 damage to any opponent.
The opponent loses the game due to having zero or less life.