A poison is a substance that interferes with the natural functions of a living creature's body, causing injury or death, typically requiring only a very small amount. The target of a poison may resist with a successful saving throw. Poisons can be delayed or cured with spells such as delay poison and neutralize poison.
Poisons have four categories, based on how they reach the target: contact, ingested, inhaled, or injury.
Contact: These poisons are delivered the moment a creature touches the poison with its bare skin. Such poisons can be used as injury poisons. Contact poisons usually have an onset time of 1 minute and a frequency of 1 minute.
Ingested: These poisons are delivered when a creature eats or drinks the poison. Ingested poisons usually have an onset time of 10 minutes and a frequency of 1 minute.
Inhaled: These poisons are delivered the moment a creature enters an area containing such poisons and do not usually have an onset time. For most inhaled poisons, 1 dose fills a volume equal to a 10-foot cube. A creature can attempt to hold its breath while inside the area to avoid inhaling the toxin. A creature holding its breath receives a 50% chance of not having to make a Fortitude save each round. See the rules for holding your breath and suffocation. If a creature is holding its breath and fails the constitution check to continue doing so, rather than suffocating it begins to breathe normally again (and is subject to the effects of the inhaled poison if still in the area).
Injury: These poisons are primarily delivered through the attacks of certain creatures and through weapons coated in the toxin. Injury poisons do not usually have an onset time and have a frequency of 1 round.
One dose of poison smeared on a weapon or some other object affects just a single target. A poisoned weapon or object retains its poison until the weapon scores a hit or the object is touched (unless the poison is wiped off before a target comes in contact with it).
Applying poison to a weapon or single piece of ammunition is a standard action. Whenever you apply or ready a poison for use, there is a 5% chance that you expose yourself to the poison and must save against the poison as normal. This does not consume the dose of poison. Whenever you attack with a poisoned weapon, if the attack roll results in a natural 1, you expose yourself to the poison. This poison is consumed when the weapon strikes a creature or is touched by the wielder. If you have the poison use class feature (such as from the assassin prestige class or the alchemist base class), you do not risk accidentally poisoning yourself when applying poison.
Unlike other afflictions, multiple doses of the same poison “stack,” meaning that successive doses combine to increase the poison's DC and duration.
Making your initial saving throw against a poison means stacking does not occur—the poison did not affect you and any later doses are treated independently. Likewise, if a poison has been cured or run its course (by you either making the saves or outlasting the poison's duration), stacking does not occur. However, if there is still poison active in you when you are attacked with that type of poison again, and you fail your initial save against the new dose, the doses stack. This has two effects, which last until the poisons run their course.
Increased Duration: Increase the duration of the poison by 1/2 the amount listed in its frequency entry.
Increased DC: Increase the poison's DC by +2.
These increases are cumulative (a third dose adds another 1/2 of the frequency to the duration and +2 to the DC, and so on). When affected by multiple doses of the same poison, you only make one saving throw at this higher DC when required by the frequency, rather than one saving throw against each dose of the poison.
Multiple doses do not alter the Cure condition of the Poison, and meeting that Cure condition ends all doses of the poison.
Applied contact poisons and injury poisons cannot inflict more than one dose of poison per weapon at a time (because the poison on the weapon only lasts for one successful attack before it wears off). Inhaled and ingested poisons can inflict multiple doses at once.
Doses from different poisons (such as an assassin with greenblood oil on his dagger and Medium spider venom on his short sword) do not stack—the effects of each are tracked separately.
Example: A fighter is facing three Medium spiders (which inject Medium spider venom on a successful bite). Medium spider venom normally has a frequency of 4 rounds and a DC of 14. On the first round, all three spiders bite him and he fails all three saves. The second and third doses each increase the total duration by 2 rounds (half of the 4 round frequency) and the save DC by +2, for a total duration of 8 rounds (4 + 2 + 2) and DC 18 (14 + 2 + 2). Fortunately, Medium spider venom is cured after just one successful save, even though the fighter is battling three doses at once.
Example: This time, the fighter makes two of his initial saves against the spider venom, so he only has one dose active in his body. He fails his save on his turn. On the spiders's turn, two of them bite him, and he fails both saves, which increases the duration to 8 rounds and the DC to 18, just as if he had failed all three saves in the same round.
You can make poison with the Craft (alchemy) skill. The DC to make a poison is equal to its Fortitude save DC. Rolling a natural 1 on a Craft skill check while making a poison exposes you to the poison. This does not consume the poison. If you have the poison use class feature, you do not risk accidentally poisoning yourself when applying poison.
The sample poisons listed below represent just some of the common poisons available in cities. Of course, most cities have laws against buying, selling, or crafting poison.