ive had this idea for ages but ive never really done anything about it. i think its been in my mind since before last brawl maybe?
anyway, the dying poison mechanic gives poison counters and overrides any existing ones. when applied, it decreases by 1 each turn until it dies out. creatures and cards that inflict this will have a low cost and high poison damage (maybe 2 for example) this is because, if the upkeep isnt kept, the poison will quickly die out and will need to be restarted.
the poison decreases after it deals damage
2 examples of how to use it:
1. a defence against other poisons- its less situational than purify and can override any poison counters
2. offensive capabilities- since it deals damage before counter goes down, it is more offensive than other poison counters. if the upkeep is held of course