Rules Index

Chapter 9: Playing the Game / General Rules / Damage / Step 3: Apply the Target's Immunities, Weaknesses, and Resistances


Source Core Rulebook pg. 453
If you have a weakness to a certain type of damage or damage from a certain source, that type of damage is extra effective against you. Whenever you would take that type of damage, increase the damage you take by the value of the weakness. For instance, if you are dealt 2d6 fire damage and have weakness 5 to fire, you take 2d6+5 fire damage.

If you have more than one weakness that would apply to the same instance of damage, use only the highest applicable weakness value. This usually happens only when a monster is weak to both a type of physical damage and the material a weapon is made of.