Triumph of the Hordes by paying ({2} magic symbol) ({G} magic symbol) ({G} magic symbol) , giving creatures you control infect until end of turn.
Cast
Windfall by paying ({2} magic symbol) ({U} magic symbol) , causing each player to discard their hand and then draw a number of cards equal to the greatest number of cards a player discarded this way.
Razorkin Needlehead triggers for each card drawn this way, giving each opponent a poison counter for each card they drew.
Each opponent loses the game due to having ten or more poison counters.