Damage

When your attack succeeds, you deal damage. The type of weapon used determines the amount of damage you deal. Effects that modify weapon damage apply to unarmed strikes and the natural physical attack forms of creatures.

Damage reduces a target’s current hit points.

Minimum Damage
If penalties reduce the damage result to less than 1, a hit still deals 1 point of damage. The only exception is if the target has damage reduction.

This does not apply to Reaper difficulty. Damage can be reduced to zero.

Strength Bonus
When you hit with a melee or thrown weapon, including a sling, add your Strength modifier to the damage result. A Strength penalty or a bonus - the latter only if you have the feat Bow Strength - applies on attacks made with any bow. Certain weapons use different ability modifier on damage rolls (list).

Off-Hand Weapon
When you deal damage with a weapon in your off hand, you add only ½ your Strength bonus. Note that monks get their full Strength bonus to off-hand unarmed attacks.

Wielding a Weapon Two-Handed
When you deal damage with a weapon that you are wielding two-handed, you add 1½ times your Strength bonus.

Multiplying Damage
Sometimes you multiply damage by some factor, such as on a critical hit. Roll the damage (with all modifiers) multiple times and total the results. Note: When you multiply damage more than once, each multiplier works off the original, unmultiplied damage.

Ability Damage
Certain creatures and magical effects can cause temporary ability damage (a reduction to an ability score). This damage is specific to one (or more) Abilities. In some cases this reduction disappears over time, but usually it requires visiting a shrine or tavern to remove the penalty. See Ability Damaged for more information.

Elemental/Alignment/Special damage
These various damage types can be found as additional damage on weapons, as base damage from spells, and occasionally as additional damage from class enhancements.

There are 9 types of elemental damage (with "elemental" being a loose use of the term for some of these):

Acid
Damage caused by caustic or corrosive substances. Acid is typically a pretty solid damage type, as fewer things resist it than fire or cold. Non-black Abishai, most Demons and Devils, Golems, Helmed Horrors, most Quori and some Spiders have resistance to acid damage. Acid-Scar Troglodytes, Acidstone Elementals, Black Abishai, Black Dragons, Green Hags, Thaarak Hounds, Will o' Wisps and Yugoloths are immune to it. A few monsters, such as Trolls, take extra damage from acid. Arcane Oozes, Clay Golems and green Dream Scourges are healed by acid.

Cold
Damage caused by ice or low temperatures. Many things take extra damage from cold, but a lot of things are also resistant to it. Arcane Oozes, Bralani Eladrin, most Demons, Dream Reavers, Ghaele Eladrin, Fiendish Gnolls, Fiendish Lions, Fiendish Scorpions, Fiendish Spiders, Fiendish Troglodytes, Golems, non-cold form Helmed Horrors, Manticores, most Quori, Will o' Wisps and some Worgs have resistance to cold damage. White Abishai, Flameskulls, Frost Beholders, Frost Giants, Gray Oozes, Gelatinous Cubes, Ice Elementals, Ice Flensers, Ice Spiders, Liches, Nightcrawlers, Night Hags, Skeletons, White Dragons and Winter Wolves are immune to it. Black Puddings, Fire Reavers, Magma Brutes, Efreeti, Fire Elementals, Fire Giants, Fire Mephits, Forgewraiths, standard Hellhounds, Pyrachnids, Red Dragons, and Salamanders take extra damage from cold. Cold form Helmed Horrors and blue Dream Scourges are healed by cold.

Electricity
Damage caused by lightning or electric shock. Few things resist electricity, but few things are weak to it either. It is, however, unable to damage any Demon, Devil or Good Outsider, making it utterly useless in chains such as Trials of the Archons. Flameskulls, most Golems, non-lightning form Helmed Horrors, Ochre Jellies, some Plant Creatures, Tieflings, Vine Stalkers, Wildmen, Windlasher Gnolls, Wood Woads, some Worgs and Yugoloths have resistance to electricity damage. Blue Abishai, most Angels, Blue Dragons, Bralani Eladrin, most Demons and Devils, Gelatinous Cube, Ghaele Eladrin, Liches, Shambling Mounds, Storm Giants and Will o' Wisps are immune to it. Green Dream Scourges take extra damage from electricity. Flesh Golems and lightning-form Helmed Horrors are healed by electricity.


 * Fire
 * Force
 * Light
 * Sonic
 * Negative
 * Poison

There are 4 alignment damages:
 * Evil
 * Good
 * Law
 * Chaos

Note that being of a certain alignment does not automatically provide immunity to an alignment damage source! For example, evil creatures can suffer evil damage, unless they are specifically immune or resistant.

There are three special damage types:

Rust
Rust damage affects only Construct and Living Construct monsters. It is a very rare damage type, appearing only on an a couple of items and the attack of a Rust Monster.

Bane
Bane damage is dealt when attacking a monster with a weapon of the appropriate Bane enchantment, or attacking one of your Favored Enemies. Nothing is resistant, immune or vulnerable to it.

Untyped
Damage that doesn't fit into any of the above categories (or the standard Bludgeoning, Piercing or Slashing weapon types) counts as untyped damage. Again, nothing is resistant, immune or vulnerable to untyped damage.

The Floating Damage Text shows how much damage of each type is dealt on each hit.

Percentage bonus
Certain rare effects increase all weapon damage by a certain percentage:
 * Champion of Good: 3% Sacred bonus
 * Crusade: 10% Enhancement bonus
 * Chant of Power: up to +6% Music bonus
 * Relentless Fury: 5% Enhancement bonus

Damage by Color
By default*, when you hit a target, the amount of damage inflicted will be shown above that target, orange by default for generic damage (and all killing shots). If the damage has any special modifiers, that damage will appear as a different color - see Monster DR and weaknesses for complete overview.
 * * This can be turned off, or the colors customized, in your Options: Ctl + o, "UI Settings", listed toward the bottom.


 * Orange numbers show normal damage.


 * Purple numbers show extra damage.


 * Yellow numbers show reduced damage.


 * Green numbers indicate target healing. (Some rare enemies are actually healed by certain damage types! e.g. Avatar of Juiblex.)

Other specific shades indicate variations on those main categories.