Stack

Abilities or skills that "stack" add their effects together. For example, modifiers of +1 Save all and +2 Save against fear "stack" to create a total +3 to Save versus fear (in addition to the +1 to Save against everything else).

In most cases however, only the strongest effect applies. For example, having non-stacking +3 and +5 modifiers is only worth a +5 bonus, not +8.

Stacking follows a few predictable general rules:


 * Bonuses usually (but not always) have a keyword, such as "enhancement" or "resistance", identifying what type of bonus it is. Bonuses of the same type do not stack.
 * Dodge bonuses to AC are a partial exception to this. Dodge bonuses of different values do stack.
 * Enhancement bonus to AC from armor stacks with Enhancement bonus to AC from shield.
 * An "armor bonus" to AC granted by a non-armor and non-docent item does not stack with an actual armor. A "shield bonus" to AC does not stack with an actual shield.
 * Some keywords like "exceptional bonus" stack with everything except themselves; a +1 exceptional bonus to Charisma will stack with everything except another +1 exceptional bonus to Charisma. It will stack with a +2 exceptional bonus to Charisma.
 * Untyped bonuses stack. Note that a bonus without a keyword isn't necessarily an untyped bonus, the description might just be lacking.
 * Penalties stack.
 * Feat bonuses stack. A character with Lightning Reflexes (+2 bonus to Reflex saves) and Luck of Heroes (+1 bonus to all saves) will have a +3 Reflex save.
 * Bonuses from character Enhancements are almost always untyped, and thus stack. They are not automatically "enhancement bonuses".
 * Benefits from the same family, like Fortification or False Life, do not stack.
 * Damage Reduction does not stack (eg. Stoneskin), except for the added DR that comes from active blocking (therefore, does stack with barkskin which is an increase to AC, ie, an unrelated modifier).
 * If you use a bow or crossbow, bonuses and properties on your weapon do not stack with ones from the same category on your ammunition. For example, using +3 bolts of lesser undead bane in a +1 flaming crossbow of lesser undead bane gives your shots +3 to attack and damage (not +4), flaming damage, and lesser undead bane effect once.

Players usually try to maximize the potential of their characters in a given area by giving them a collection of bonus with different keywords. Achieving a high Armor Class is a good example of this strategy.

Spell damage
For information about stacking of various spell damage effects, refer to Spell Damage.