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, Crimson Foot Spiders, most Demons and Devils, Golems, Helmed Horrors, and most Quori 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. 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, Fiendish Trolls, 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, Efreeti, Fire Elementals, Fire Giants, Fire Mephits, Forgewraiths, standard Hellhounds, Magma Brutes, 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 Cubes, 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

Damage caused by intense heat. Many monsters are vulnerable to fire damage, but a high number also have some form of resistance to it. Non-red Abishai, Arcane Oozes, most Demons and Devils, Dream Reavers, Fiendish Bats, Fiendish Gnolls, Fiendish Lions, Fiendish Scorpions, Fiendish Spiders, Fiendish Troglodytes, Fiendish Trolls, Firebrand Gnolls, most Golems, non-fire form Helmed Horrors, most Quori, Tieflings, Wildmen, Will o’ Wisps, and Yugoloths have resistance to fire damage. Red abishai, Blackbone Skeletons, Efreeti, Fire Elementals, Fire Giants, Fire Mephits, Fire Reavers, Flame Eaters, Flameskulls, Forgewraiths, Gray Oozes, Hellhounds, Magma Brutes, Muckmen, Night Hags, Pyrachnids, Red Dragons, and Salamanders are immune to it. Blue Dream Scourges, Frost Beholders, Frost Giants, Frostmarrow Skeletons, Ice Elementals, Ice Flensers, Ice Mephits, Ice Spiders, Mummies, Scarecrows, standard Trolls, Twig Blights, White Dragons, and Winter Wolves take extra damage from fire. Cinderspawn, red Dream Scourges, fire form Helmed Horrors, and Iron Golems are healed by fire.

Force

Damage caused by pure arcane energy. A very powerful damage type, as basically nothing except Golems resist force, and nothing is immune to or healed by it. Will o' Wisps are vulnerable to force.

Light

Damage caused by extremely intense light. A rare but powerful damage type, as several things are vulnerable to light - namely, Black Puddings, Evil Eyes, Forgewraiths, Nightcrawlers, Shades, Shadow Dragons, Shadows, and Vampires - but only Golems and Will o' Wisps resist light, and nothing is healed by or immune to it.

Sonic

Damage caused by extremely loud sound. Another extremely powerful damage type - nothing except Golems and Will o' Wisps resist it. Nothing is immune to, vulnerable to, or healed by sonic damage.

Negative

Damage caused by negative energy (essentially, anti-life force.) Nothing resists or is vulnerable to negative damage, but all Constructs and Living Constructs are immune to it. In addition, all Undead are healed by negative.

This is one of two elements players can be totally immune to. Warforged are unaffected by negative damage. If you're a Pale Master wearing a Pale Shroud, negative damage will actually heal you.

Poison

Damage caused by toxic chemicals. Not for nothing is poison considered D&D's weakest damage type, as in addition to all Constructs, Elementals, Living Constructs, Oozes and Undead, poison has no effect on Green Abishai, Angels, Demons, Driders, Drow Scorpions, Fiendish Spiders, Gargoyles, Green Dragons, Scorpions, Spiders, Will o' Wisps, Yuan-ti, and Yugoloths. To top it all off, nothing is vulnerable to it.

Nothing is resistant to or healed by poison damage. Players with a Warforged or shrouded Pale Master are also immune to poison damage.

There are 4 alignment damages:

Evil

Damage caused by things like evil aligned weapons, Unholy Blight or similar spells, or Bearded Devils. Tends to deal no damage to Evil Outsiders and double damage to Good Outsiders.

Good

Damage caused by things like good aligned weapons, Deific Vengeance or similar spells, or some Angels. Tends to deal no damage to Good Outsiders and double damage to Evil Outsiders.

Law

Damage caused by things like lawful aligned weapons, Order's Wrath or similar spells, or Maruts. Tends to deal no damage to Lawful Outsiders and double damage to Slaadi.

Chaos

Damage caused by things like chaotic aligned weapons, Chaos Hammer or similar spells, or Slaadi. Tends to deal no damage to Slaadi and double damage to Lawful Outsiders.

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 four 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.

Positive

Positive energy usually heals players, but also deals damage to Undead type opponents.

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.

(Note: The sections of these descriptions describing which monsters are resistant and so forth to each damage type are only a generalisation and do not account for unique resistances in some monsters. For example, some scorpions in Menechtarun have sonic resistance but the Scorpion race in general does not.)

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.