When a Siege is cast, its controller must pick an opposing player to be its defender
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If you were to lose due to poison counters, you would immediately lose as soon as the ability resolves as you still have 10 poison counters
If you play a lot of constructed Commander, these decks arent any more complicated than player constructed decks, but theres a lot of triggered/activated abilities, +1/+1 counters, and various mechanics from all over Magic inside them
This will likely be much cleaner in digital Magic when you always have the right counter, counters cant slide or be blown off a creature, and you get visual indications like a creature floating above the battlefield in Magic Arena
I personally use one for dice, and one for glass beads