What is Poison?
Poison is a Damaging Ailment that deals Chaos Damage over time by default and is usually inflicted by a Hit. The base Damage that's dealt by Poison only accounts for the total combined Physical and Chaos Damage in a Hit. Poison is limited to a single stack on targets by default, but this limit can be increased through various sources such as Comorbidity. All inflicted Poisons will exist on a target and remain for their full duration, but only the highest Damage Poison(s) will have any effect, up to your limit of inflicted Poisons.
Energy Shield and Poison
The Chaos Damage dealt by Poison directly bypasses Energy Shield to deal Damage to Life. Unlike Bleeding, Poison can be inflicted on a target regardless of the existence of any Energy Shield.
Chance to inflict Poison
Chance to inflict Poison can be obtained from various Passive Skills, Support Gems and gear modifiers. For example Envenom grants '50% chance to Poison on Hit' for the supported Skill. Modifiers that increase your chance to inflict Ailments, for example the '15% increased chance to inflict Ailments' on the
Exposed Wounds Passive tree notable, will act as a multiplier to your chance to inflict Poison and will not add their percentage directly to this stat. Reaching 100% chance to inflict Poison is important for a build that's relying on this Ailment to deal the majority of its Damage output.
Magnitude of Poison
By default the Magnitude of Poison is 20% of the combined Physical and Chaos Damage of the Hit that inflicted the Ailment, dealt as Chaos Damage per second. You can improve the Magnitude of Poison by investing into relevant modifiers, such as
Crippling Toxins's '25% increased Magnitude of Poison you inflict', which alone would increase the base Magnitude of Poison to deal 25% of the combined Physical and Chaos Damage of a Hit per second. Note: modifiers to Magnitude do not affect Poison Duration.
Modifiers that apply to the Effect of Poison, such as
Low Tolerance, act as multipliers to the Magnitude of Poison.
Calculating the Damage of Poison
The amount of Damage dealt by Poison is determined by the final combined Physical and Chaos Damage dealt by a Hit prior to the target's mitigation. This includes any modifiers you have that would scale the Hit Damage for the Damage type(s) being used to inflict Poison. For example, if you're inflicting Poison with a Hit that only deals Physical Damage, modifiers that increase Chaos Damage wouldn't scale the Hit, and therefore they also wouldn't scale the inflicted Poison Damage even though it's dealing Chaos Damage. This is because your Damage modifiers are only applied once to the Hit to determine the Magnitude of Poison - they won't be applied a second time to the Ailment itself.
Duration of Poison
Poison has a 2 second Duration by default and can be improved with modifiers to Ailment or Poison Duration. Increasing the Duration of Poison will increase the total Damage dealt across the full Duration of the Ailment, but not the Damage dealt per second. Modifiers that make Ailments deal their Damage faster, for example
Fast Acting Toxins, will improve the Damage dealt per second by Poison by making the Ailment deal its full Damage faster, essentially shortening its Duration.
Limit of Poison Stacks
By default, Poison is limited to 1 stack on a target. This limit can be improved by obtaining various modifiers:
- Comorbidity (Support Gem)
Stacking Toxins (Passive Tree Notable)
Building Toxins (Passive Tree Notable)
Snakebite (Unique Gloves)
Overwhelming Toxicity (Pathfinder Ascendancy Notable)
A Pathfinder can therefore reach a limit of 10 stacks of Poison on targets by combining all of the above, while other classes can reach a maximum of 5.