“Effects with this trait deal acid damage. Creatures with this trait have a magical connection to acid.”

Rules for energy damage define acid as one of the main types of energy damage, noting that acid damage “can be delivered by gases, liquids, and certain solids that dissolve flesh, and sometimes harder materials.” Mechanically, acid damage follows the same general procedure as other damage types: roll damage, determine type, apply any immunity, resistance, or weakness, then subtract the remainder from Hit Points.

Energy damage and interactions

Acid sits in the same mechanical family as other energy types:

It is an energy damage type, treated similarly to cold, electricity, fire, and sonic for purposes of resistances and weaknesses.

Characters and monsters may have acid resistance (reducing each instance of acid damage), acid immunity (ignoring it entirely), or occasionally weakness to acid, which increases each instance of acid damage taken.

Designer analysis has noted that, in PF2e’s bestiary data, acid is resisted by fewer creatures than fire, cold, or electricity, but also has very few explicit weaknesses, making it a steady, reliable energy type rather than a highly exploitable one.