Sorry, team -- we seem to have stalled.
Antitoxin: is preventative. Miss Imogen has two doses, and Harb has one that I know of (IC 704, 708).
Healing potions: I think I have been lax here. My character sheet lists three potions, but I know at least one has been drunk, and possibly 2 or three. I didn't keep good records oon this, I'm afraid. I'd like there to be one left, but if anyone's memory is better than mine, I will happily defer -- it is quite possible they are all gone.
Effects of poison. I realize that I don't know the effects of poison on the dying. When I post, I will act on the following assumption:
1. That once unconscious, poison does not continue to cause hitpoint loss.
2. That once stabilized, it requires another "hit" before death saves begin again (i.e. that autodamage from poison [if any] wouldn't restart it immediately.)
3. Chrysagon, restrained and Unconscious (and failing a death throw this round) needs treatment right away.
4. That the vine could easily attack him again this round, and any damage will cause a death save failure.
If this is so my plan is to make an untrained medicine check to stabilize (with Weed's help?), or to apply a potion if there is one [in which case Weed could apply an antitoxin once he's conscious?], rather than shoot an arrow.