Cast Triumph of the Hordes by paying ({2} magic symbol) ({G} magic symbol) ({G} magic symbol) , giving creatures you control +1/+1, trample and infect until end of turn.
Deal combat damage to an opponent using Hydra Omnivore, causing them to get at least nine poison counters.
The opponent loses the game as a state-based action due to having ten or more poison counters.
Hydra Omnivore triggers, causing each other opponent to get at least nine poison counters.
Each remaining opponent loses the game as a state-based action due to having ten or more poison counters.