With so many elves being small creatures that get bigger later, this commander can leave you with an absolutely massive Gyre Sage
By ensuring your enemy accumulates ten poison counters, you win the game
Sticky notes or tape
(If this creature isn't monstrous, put X +1/+1 counters on it and it becomes monstrous.) When Polukranos, World Eater becomes monstrous, it deals X damage divided as you choose among any number of target creatures your opponents control
What makes Split Up so damned good is that you get the choice between blowing up tapped creatures or untapped creatures
Firkrag notably provides additional value for goading, as whenever a creature deals damage to one of your opponents, if it had to attack such as through a goading effect, you can put a +1/+1 counter on Firkrag, drawing a card in the process