{Sabertooth Cobra}
If this card deals damage to a player multiple times, does the listed ability stack? I.E. If a player is hit with damage for the second time, does that player have to pay 4 colorless to prevent receiving no more poison counters during the next upkeep?
Yes. There would be two separate delayed triggered abilities, both of which would go off at the beginning of that player's next upkeep.
The really evil thing about this card is that it makes them pay the mana before their turn. If you hit them while they're tapped out, they're out of luck!
Awesome! Thanks for the quick reply. This card truly is evil!