Building Up Immunity to Poison

[Revilo]

Had my party face a few drow assassins, each of them carrying a vial of drow poison. When they looted the corpses, an interesting question came up. Could the party steadily build up a resistance or eventual immunity to a poison? Drow poison in particular in this case, but I kind of like the idea for any particular poison you really don't like. Is there a system/way of doing this kind of thing anywhere? Official rules, homebrew or otherwise?

[Wheldrake]

AFAIK, there are no such rules. In real life, it is possible to build up resistance only to certain poisons such as arsenic, while other poisons will simply accumulate and cause illness or death rather than "mithridatize" someone.

So it's up to the DM to decide if this works. It should take a significant duration in time, as well as a supply of the given poison, and eventually provide a bonus to saves rather than complete immunity. It would be a house rule, though.

[Bacon666]

I played in a game once where we had houserules for this.

It was a very house ruled 3.5 game, where our gm wanted us to run various businesses, and make up our own profession skills, knowledge skills etc.

Depending on this he gave abilities that would evolve as we levelled up...

My char was an inn keeper / inn owner with knowledge (spirits) and craft (alcohol) and craft (poison)

My ability was that for each rank I put into ALL theese skills I could experiment with one poison and gain resistance 5 (stackable) at 25 it would become immunity...

Being an innkeeper I put 4 ranks in each at level 1 (3.5 remember...) And wrote in the "experiments" into my background for resistance 20 to alcohol :-D

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For a permanent houserule I would tone it down to something like:

1 dose of poison slowly applied over 10 days (10 saves with +4 to the save for small dose)

If all saves ate made grant +4 circumstance bonus vs. that poison
5-9 saves made grant +2
0-4 saves made = no gain

To keep the bonus one dose of the poison must be "used" every 2 months

[CraziFuzzy]

Only Iocane...

No, there are no rules for it. I don't think I'd let him gain immunity to it, but perhaps a resistance toward that particular poison. Perhaps for each time he successfully saves against the poison, he could gain a cumulative bonus to his saving throw against that poison (max bonus equal to his CON modifier).

Drow poison, being pretty weak, would be a pretty safe poison to do this with, as long as the characters knew they'd have a day or so to recover from the effects.

[Imbicatus]

There is a trait normally only available to halfling worshipers of Norgorber that is perfect:venom drenched a gm may allow this to be taken by others.