I have never liked the "save or die" option. Poison simply doesn't affect people this way. Many poisonings give plenty of time for people to get to the hospital and be saved, as we well know. A person could easily spend a full year building up a very complicated system and set of rules to describe all the variable forms of poison, but for what? A method of killing that is, frankly, somewhat dull compared to hacking people to death with a sword.
Still, poison has to exist so waving it away is not an option. I've been steadily working up my own rules to deal with poison, partly on the wiki and partly in my head. I've gone an extra step today (in keeping with
working on medicine/physician rules) to codify these rules further. I include part of the relevant wiki page below:
Because poison attacks a creature from the inside, the amount of damage that is done is PER hit die or level, meaning that creatures with a high number of hit dice or levels are no safer from poisoning than creatures with less. A 1st level character, therefore, has as much chance of surviving being poisoned as a 10th level creature. This keeps in line with my rules defining biological units (see Hit Points). Most poisons range from a lethality of 1 to 10 points per hit die or level.
For example, a 5th level fighter and a 1st level fighter are each poisoned by a substance with a lethality of 5 hp/HD & Level. Because leveled creatures do possess 1 HD in addition to their levels (see Hit Dice), the 5th level will suffer 6 x 5 hp (30 damage) and 1st level will suffer 2 x 5hp (10 damage). In my game, an average 5th level NPC fighter would have 32 total hit points: a d8 (for mass, counting as the character's 1 HD) + 5d10. The 1st level NPC fighter would receive a d8 + 1d10, for 10 hit points. Each would suffer an amount of damage that would seriously threaten their survival, particularly if either had already suffered damage from other means. Any constitution bonus would greatly increase their chance of survival.
Likewise, we might compare an Indian elephant with 10 hit dice to the above, encountering the same poison. The elephant would suffer 50 total damage - but because the elephant weighs about 5 to 6 tons, it has an average of 9.5 hp/HD, or an average of 95 hit points.
Time of Effect
The damage caused by poison does not affect the victim all at once. To begin with, the poison must have time to enter the bloodstream and spread through the body: this alone will require 1 to 3 rounds, during which time the poison will cause no damage of any time. Once this time has passed, the actual damage caused by the poison is then a random roll from round to round, according the following formula:
- Divide the total damage caused by the poison in half: this indicates the potential maximum effect (PME) of the poison per round.
- Each round, roll a die equal to the PME and remove the damage that has been done from the initial total.
- When the PME is less than the total damage remaining, reduce the PME to equal this remainder for each round that remains.
- Continue to roll each round until all damage has been suffered.
With the 4th round we roll a 2 and Ethan's free action is still unaffected. In the 5th round, however, we roll an 8 and Ethan is now definitely stunned. He has taken a total of 14 hit points so far, so in the 6th round the PME is unchanged: Ethan takes another 6 damage and is in trouble. Thankfully, however, he is probably past the worst: because he has taken 20 damage so far, the PME is reduced to 10 points. In the 7th round we roll 1-10 and Ethan suffers another 5 damage. We reduce the PME again and in the 8th round, we roll 1-5 and Ethan suffers 4 more damage. This leaves only 1 left, so that in the 9th round he takes this last damage and the poison has run its course.
While this does impose a more complicated procedure where calculating the damage done by poison, it does increase the game's tension where it comes to the character being unsure of how bad the poison really is. There is also time to give aid, allaying the damage caused by the poison with spell, potion or salve while it is happening, casting slow poison or neutralize poison if possible. Therefore, it is possible for a character to suffer more damage than initially possessed at the start of being poisoned. It also means that multiple poisonings (from monster attacks or consuming more than one dose before realizing the poisoning has occurred) could produce multiple PME rolls per round.
Saving throws against poisoning will reduce the total damage of the poison (and the PME as well) by 50%. Recognizing that a substance is poisoned before drinking is not considered part of a saving throw, but is a sage ability in its own right.
I intend to add this last (the ability to be able to smell/locate poison) to the assassin character's poison study ability.