1. Perhaps make a creature that creates an immunity to poison after having it for 2 turns. If devoured, the immunity is passed on, and would remove 1? poison counter a turn (like fighting an bad infection takes a few days). I think it would probably be a life creature.
2. Make a new weapon called Syringe | Big Syringe.
The ability would be like 2
: Extract poison from target creature (max of 5 poison counters at a time?)
Aside from dealing 1 damage a turn, the poison extracted could be fired for extra damage.
Probably an Other weapon