- This article is about the overall bonus to the attack roll; for the item property, see Attack bonus (item property).
The attack bonus (AB) is a number added to a roll of a d20 whenever a creature makes an attack. This total is then compared to the target's armor class to see if the attack hits hard enough to deal damage (before things like damage reduction are considered). The attack bonus is the sum of the base attack bonus, an ability modifier, the higher of weapon attack or enhancement bonus, bonuses from spells and spell-like abilities, modifiers from feats, and possibly several situational modifiers.
base attack bonus + ability modifier + weapon bonus + spells + feats + situational
In melee combat, the strength modifier is used, unless the attacker has weapon finesse and a higher dexterity modifier than strength. In that case, the dexterity modifier is used. In ranged combat, the dexterity modifier is used, unless the attacker has zen archery and a higher wisdom modifier than dexterity. In that case, the wisdom modifier is used.
While bonuses from different spells stack, there is a +20 attack bonus cap to the total of bonuses from the weapon and spells (and spell-like abilities). Feats that are invoked (e.g. bard song) generally fall under the cap as a spell-like ability. Feats that are toggled (e.g. expertise), situational (e.g. bane of enemies), or always on (e.g. epic prowess) generally do not contribute to the +20 cap, but instead stack with no limit.
Situational modifiers apply when certain conditions are met (not counting the condition of having a certain feat, as those fall under feat modifiers). The various situational modifiers are as follows.
- Melee
- Target is prone. +4AB
- Ranged
- Attacker is mounted. -4AB (or -2AB with mounted archery)
- Target is moving. -2AB
- Target is prone. -4AB
- Target is within 3.5 meters of the attacker. -4AB (unless negated by point blank shot)
The mounted penalty only applies in modules that are designed with horses in mind and that have specifically turned on this penalty. This particular penalty is unusual in that it does contribute to the net +20 cap, unlike other situational modifiers.
- Always
- Attacker's size modifier. -2 to +2 AB
- Attacker is invisible or target is blind. +2AB (unless negated by the target's blind fighting)
- Target cannot be seen (hidden, invisible, or out of visual range). -4AB
- Target is flanked. +2AB (unless negated by the target's defensive awareness)
- Target is stunned. +2AB
The bonus for invisible attackers does not apply if the attacker can see through its own type of invisibility (a bug). Being out of visual range typically only applies to non-player characters making ranged attacks in response to being attacked (since players cannot target creatures outside their characters' visual range).
Decreasing AB
The following spells can be used to directly decrease an enemy's attack bonus: bane, battletide, Bigby's interposing hand, flare, and prayer.
The following (class-specific) feats can be used to temporarily directly decrease an enemy's attack bonus: curse song.
Increasing AB
The following combat feats can be used to directly increase the attack bonus for a single attack (none subject to the cap): disarm (if using a larger weapon), smite evil, and smite good.
The following spells can be used to temporarily directly increase their targets' attack bonus (all subject to the +20 cap): aid, awaken, battletide, blade thirst, bless, bless weapon, divine favor, divine power, greater magic fang, greater magic weapon, holy sword, magic fang, magic weapon, prayer, true strike, and war cry.
The following (class-specific) feats can be used to temporarily directly increase their targets' attack bonus (all subject to the +20 cap): bard song, divine wrath, oath of wrath, rallying cry, and war domain.
The following general feats directly increase attack bonus (none subject to the cap): bane of enemies (ranger class only), epic prowess, epic weapon focus, point blank shot (ranged combat only), and weapon focus.
The following class and racial feats directly increase attack bonus (none subject to the cap): battle training vs. goblins, battle training vs. orcs, battle training vs. reptilians, enchant arrow, epic superior weapon focus, good aim, nature sense, opportunist, and superior weapon focus.