I'm not 100% sure this is the best way ever to handle poisons in game, or anything like that. But it is a bit different, allows for a few different types of effects of different poisons, and tries to remain simple enough. It does require a bit of reference-checking for me still, but I think if I played with these poison rules long enough, I'd probably get them down in my head without needing to look them up.
I have divided poisons into four types (the names are not really relevant to their real world meanings, necessarily). Each does some damage over time, but also has another "side effect" such as sleep, paralysis, sensory deprivation, pain/vomiting/diarrhea/other hindrances, mental stupor, and yes, instant death. It may require a bit of extra book-keeping, but it also allows GMs to ignore any of the types they don't like. If you don't want Vizzini to just keel over a few seconds after drinking iocaine-laced wine, don't use the deadly poisons in your game.
|No save-or-die poisons? Inconceivable!|
And to quit rambling on about it before anyone besides me really knows what I'm talking about, here are the snippets of rules from the draft. First are the players' side prices and types of poison commonly available (at least for criminals or Shinobi) from the equipment lists (mon is the standard silver coin of the realm, equal to a normal D&D gold piece).
The actual game effects are kept "behind the screen" so GMs can choose to add a bit of uncertainty with respect to duration/damage dealt when PCs use poison on monsters if they choose. Or, if they want they can reveal the mechanics behind the poison to the players. Those mechanics are (as they currently stand) found in the Combat Rules section of the text:
A few notes: AC is of course armor class, TD is Tactical Defense - like AC, but for special maneuvers like disarm/trip/wrestle etc. (borrowed idea from Pathfinder). TN is target number.
*Save or die is simple. There's not really much you need to worry about remembering during an often messy, chaotic battle, or typical rambunctious RPG session. You get bitten by a giant spider and test your luck. Done.