Damage and stacking
Three different things reduce a hit, and they are applied in this order:
- Damage immunity, a percentage, taken off the total.
- Damage resistance, a flat amount, taken off each type separately.
- Damage reduction, a flat amount, taken off physical damage.
A creature with 50% fire immunity and fire resistance 20 hit for 100 fire takes 50 after the immunity, then 30 after the resistance.
Damage immunity
Damage immunity removes a percentage of one damage type. A vulnerability adds a percentage instead. Percentages of the same type add together, from items, spells, feats and race alike, and the total is capped at 100%. A vulnerability of the same type cancels an immunity point for point.
While the net immunity is above 0%, at least 1 point is always absorbed: 1% immunity against a 10-point hit absorbs 1 point, not 0.
Damage resistance
Damage resistance removes a flat amount of one damage type from every hit: fire resistance 20 absorbs the first 20 fire damage of each hit. No weapon bypasses it.
Resistances do not stack: for each type, only the highest from a spell or an equipped item counts. The exception is the energy resistance feats, which stack with the rest and are applied before it.
Each damage type on a weapon is resisted separately, so one hit can meet several of your resistances. A weapon dealing two physical types is resisted at the lower of the two.
Damage reduction
Also called soak. It is written 20/+3: it ignores the first 20 points of physical damage from any weapon whose enhancement is below +3. Feats and class abilities give it as 20/-, which no weapon bypasses.
- Reductions do not stack. The one that soaks the most, among those the attacker's weapon does not bypass, applies. On a tie the oldest one applies.
- The exceptions: the epic damage reduction feats stack with Perfect Self, and the X/- sources - Barbarian, Dwarven Defender and the epic feats - stack with each other.
- A creature attacking with its own natural weapons bypasses damage reduction up to its own: a creature with 10/+5 bypasses any damage reduction up to X/+5. Its X/- reduction does not count for this.
What stacks, and how far
| Stacks | Ceiling | |
|---|---|---|
| Ability score bonuses | from different items, yes; on one item, only the highest | +12 |
| Attack bonuses | yes | +20 |
| Damage bonuses | yes | +100 |
| Saving throw bonuses | yes | +20 |
| Skill bonuses | yes | +50 |
| Damage immunity and vulnerability | yes | 100% either way |
| Armour class of different types (armour, shield, deflection, natural, dodge) | yes | - |
| Dodge armour class | yes | +20 |
| Armour class of the same type, dodge aside | no | - |
| Concealment | no | - |
| Damage reduction | no, except the sources named above | - |
| Damage resistance | no, except the energy feats | - |
| Spell resistance | no | - |
Penalties are gathered the same way and kept separate: where something does not stack, the largest bonus and the largest penalty both apply. The ceiling is applied after the two are added, so a character at +24 dodge who takes a -2 dodge penalty is still at +20.
A single item cannot carry more than +12 of saving throw bonus, whatever the character's ceiling is.