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Damage mechanics

From bg3.wiki
1d4 + 1d6 Poison.png
A single attack, spell, trap, or other harmful effect can often result in multiple Damage Rolls. Determining the resulting damage from these various rolls can be difficult due to hidden mechanics which are commonly referred to by the community as damage "sources" and damage "riders". The term damage "instances" is sometimes used in place of damage "sources," but for the purpose of this page the only terms to be used are damage source(s) and damage rider(s). The game does not inform players what is a damage source vs. what is a damage rider, or how these two interact with each other. This page describes the mechanical differences between damage sources and damage riders, how they interact, and lists which effects and abilities fall into each category.

Damage Sources (DS) vs. Damage Riders (DR)

A damage source is an attack or other effect that directly deals damage to one or more targets. Examples include striking a target with a weapon, many spells, or thrown items such as an Alchemist's Fire. Damage sources usually require the use of an action (e.g. throwing an object such as a grenade), bonus action (e.g. making an attack with your offhand weapon while dual wielding) or reaction (e.g. the Hellish Rebuke Hellish Rebuke spell).

A damage rider is something which adds to the damage dealt by a source. A rider cannot deal its damage independently - there must be an applicable damage source for it to "ride". Examples of damage riders include the Hex Hex spell adding damage to the damage from a Warlock's Eldritch Blast Eldritch Blast or weapon attacks, coatings applied to weapons providing additional damage to a weapon attack, a 6th level Draconic Bloodline Draconic Bloodline applying their elemental affinity to a spell of the appropriate damage type, or a raging 25 25 adding bonus rage damage to their weapon attacks. Many damage riders are gained from passive features or other kinds of buffs. Any eligible damage riders from a damaging effect will be applied to a damage source which is a part of that damaging effect.

Damage Riders treated as Damage Sources (DRS)

There are some damage riders which defy the typical trends described above. They still must "ride along" with a damage source in order to be applied, but when the damage is calculated they are treated as damage sources instead of damage riders. This means that these "damage riders which are treated as damage sources" can then cause normal damage riders to be applied once again as part of the same ability (e.g. attack or spell) which caused the damage.

Nearly all DRS effects are treated like normal Damage Riders when playing on Honour mode, making much of the following information irrelevant for those players.


Example Calculation

A character with 20 Strength, the Tavern Brawler Feat, Lightning Charges (Condition) Lightning Charges (Condition), and the Ring of Flinging uses the Lightning Jabber to make a thrown weapon attack against a target which is affected by Hex Hex.

Damage Sources (DS):

  • Thrown weapon attack using the Lightning Jabber applies 1d6 (damage die) + 1 (weapon enchantment) + 5 (Strength modifier) piercing damage

Damage Riders (DR):

  • Lightning Charges (Condition) Lightning Charges (Condition) add +1 Lightning Damage to each damage source
  • The Ring of Flinging adds 1d4 damage which is of the same type as the weapon used (piercing in this example) to each damage source.
  • Hex Hex adds 1d6 necrotic damage to each damage source.
  • Tavern Brawler adds the character's Strength modifier to thrown weapon attacks an additional time

Damage Riders treated as Damage Sources (DRS):

  • The additional 1d4 damage from the Lightning Jabber is a damage rider treated as a damage source. This means it will cause all of the Damage Riders listed above to activate a second time.


Calculating total damage:

To determine the total damage applied take each DS and DRS. Then apply the damage riders onto each of these. In this example that means one should evaluate the normal damage source of throwing a spear plus all damage riders, followed by the additional lightning damage from the Lightning Jabber with all damage riders applied again.

Treating the bonus lighting damage from throwing the Lightning Jabber as DRS' means the damage roll in the above scenario would on average yield 36 total damage (ignoring resistances) calculated as follows:

As a hypothetical scenario to show the impact that this minor detail can have, instead imagine the bonus lighting damage from throwing the Lightning Jabber is treated as a DR in the above scenario. In this hypothetical scenario the above damage roll would yield 24 total damage on average (ignoring resistances) calculated as follows:

This is a simple example to demonstrate the underlying principles. By mixing and matching multiple DR and DRS effects it is possible to deal hundreds (and in extreme cases with proper conditions over thousands) of points of damage with a single attack.

DRS effects

The following are a list of items and abilities which have DRS effects, and what the relevant DRS effect is. Most of the below effects appear to instead be treated as normal damage riders for Honour mode difficulty, so the below tables should only be applied to other difficulty settings.

Weapons
Item Act Found Relevant Effect Notes
Arrow of Acid All Deals Weapon Damage + 2d4Damage TypesAcid (Dexterity Save to negate). Creates a permanent Acid Surface. N/a
Arrow of Fire All Deals weapon damage + 2d4Damage TypesFire (Dexterity Save to negate). Creates a Fire Surface for 2 turns. N/a
Arrow of Ice All Deals weapon damage + 2d4Damage TypesCold (Dexterity Save to negate). Creates an Ice Surface for 2 turns. N/a
Arrow of Lightning All Deals weapon damage + 2d4Damage TypesLightning (Dexterity Save to negate). N/a
Prepared (Condition) Prepared (Condition) All Spend 6 m / 20 ft of your movement to deal additional physical damage (minimum 1) on each successful weapon attack for the rest of the turn. Weapon Action available to all Greataxes. Recharges on Short Rest
Assassin's Touch One Deathly Slumber: Deals an additional 1d4 Damage TypesNecrotic damage to creatures that are  Knocked Out Knocked Out or Sleeping Sleeping . N/a
Deep Delver: Dig Deep One Inflicts Shattered on hit. When attacking a Shattered target, deal an additional 1d4Damage TypesPiercing damage. N/a
Dragon's Grasp: Burned Alive One Deals an additional 1d4Damage TypesSlashing damage to Burning Burning targets. Can apply multiple times.
Exterminator's Axe: Scourge of Pets One Deals an additional 1d6Damage TypesFire damage to Plants, Insects or Small creatures. N/a
Firestoker: Burned Alive One Deals an additional 1d4Damage TypesPiercing damage to Burning Burning targets. Can apply multiple times.
Hoppy: Revitalising Strike One Revitalising Strike: Smash into a foe, wounding them and healing your own injuries. On a hit, heal 1d6hit points. You deal additional  Damage TypesNecrotic damage equal to your Proficiency Bonus. This is a weapon action specific to this weapon. As with all weapon actions, it recharges on a short rest.
Loviatar's Scourge: Willing Whip One Willing Whip: Grants Resistance to Damage TypesNecrotic damage. Deals an additional 1d6Damage TypesNecrotic damage to nearby targets, including the wielder. This damage does not benefit from many damage riders that are applied to the base weapon attack. For instance when used as part of a smite attack, bonus damage applied to spells is not applied to the damage caused by the willing whip ability.
Ritual Dagger: Blood Sacrifice One Blood Sacrifice: Pain is a path to power. Take 1d4Damage TypesSlashing damage to receive a +1d4 bonus to Attack Rolls and Saving Throws. Damage riders are applied to the self inflicted damage.
Shortsword of First Blood One Break the Unbroken: Deal an additional 1d8Damage TypesPiercing damage to targets that still have all their hitpoints. The target must be at full health.
The Blast Pendant: Lightning Blast One Lightning Blast: Once per Long Rest you may focus the electricity in your veins as a bonus action. Your next lightning spell or cantrip deals additional Damage TypesLightning Lightning damage equal to your remaining Lightning Charges Lightning Charges. On a hit, all of your Lightning Charges are consumed. This is a usable once per long rest and only applies to Lightning Spells or cantrips.
Very Heavy Greataxe: Gargantuan Cleave One or Two Gargantuan Cleave: Swing your weapon with all your might. You can attack multiple targets, but become Off Balance Off Balance. This is a weapon action specific to this weapon. As with all weapon actions, it recharges on a short rest.
Blooded Greataxe: Relentless Revenge One When the wielder has 50% HP Icon.png hit points or less, they deal an additional 1d4Damage TypesSlashing damage. N/a
Phalar Aluve: Shriek One All enemies within 6m of range have a 1d4 penalty to Charisma, Wisdom and Intelligence Saving Throws. Affected creatures receive an extra 1d4Damage TypesThunder damage. The sword will stop Shrieking if unequipped. This is a weapon action specific to this weapon. As with all weapon actions, it recharges on a short rest.
Soulbreaker Greatsword: Soulbreaker One Soulbreaker: Rend the enemy's body and soul, dealing an additional 4Damage TypesPsychic damage, and possibly Stun Stun them. This is a weapon action specific to this weapon. As with all weapon actions, it recharges on a short rest.
Lightning Jabber Two Throwing: Lighting Damage: When launched at a target, deal an additional 1d4Damage TypesLightning damage. This is only works when thrown.
Render of Mind and Body: Psychic Steel Virtuoso Two When the wielder attacks with Advantage Icon.png Advantage, they deal an additional 1d8Damage TypesPsychic damage Only applies to attacks made with the weapon itself.
Moonlight Glaive: Moonlight Butterflies Two Moonlight Butterflies: Strike a foe, conjuring an illusory swarm of moon-pale butterflies, gaining Advantage Icon.png Advantage on attacks against the target. Deal additional Damage TypesPsychic damage equal to your Proficiency Bonus. When the target moves away from your illusion, it takes 1d6Damage TypesPsychic damage. This is a weapon action specific to this weapon. As with all weapon actions, it recharges on a short rest.
Punch-Drunk Bastard Two Tippler's Rage: When you have the Alcohol Alcohol condition, you have Advantage Icon.png Advantage on Attack Rolls. You also create a blast with each attack, dealing 1d4Damage TypesThunder damage for 3m / 10ft. This damage does not benefit from many damage riders that are applied to the base weapon attack. For instance when used as part of a smite attack, bonus damage applied to spells is not applied to the damage caused by the Tippler's Rage ability.
Justiciar's Scimitar: Shadowsoaked Blow Two Shadowsoaked Blow: Strike an enemy, adding your Proficiency Bonus to the damage. Moreover, if the attack hits, it also deals an additional 1d6Damage TypesPsychic damage. This attack doesn't break concealment. This is a weapon action specific to this weapon. As with all weapon actions, it recharges on a short rest.
Sword of Life Stealing Two On a Critical Hit, the target takes an extra 10Damage TypesNecrotic damage as long as it isn't a construct or an undead. You also gain 10 temporary hit points. N/a
The Undead Bane: Profane Scourge Three Profane Scourge: Strike with subjugating fury, adding your Proficiency Bonus to the damage roll. If you hit a Fiend or Undead creature, deal an additional 2d6Damage TypesSlashing damage and possibly Bane Bane it. Undead and Constructs can't Bleed Bleed. This is a weapon action specific to this weapon. As with all weapon actions, it recharges on a short rest. This weapons special bonus damage vs undead and fiends is applied to both the weapons base damage and the damage applied by the Profane Scourge weapon action.
Craterflesh Gloves: Craterous Wounds Three Whenever you score a Critical Hit, deal an additional 1d6Damage TypesForce damage. N/a
Stalker Gloves: Skullduggery Attack Three Your  Sneak Attack Sneak Attack deals an additional 1d4Damage TypesForce damage N/a
Hellfire Greataxe: Hellflame Cleave Three Hellflame Cleave: Spew hellish flames and strike your foes. On Save: Targets still take half damage. Hellfire ignores Resistance and Immunity to Damage TypesFire damage. This is a weapon action specific to this weapon. As with all weapon actions, it recharges on a short rest. This weapon action counts as a spell for effects that add bonus damage to spells. Bonus damage is applied to the base weapon damage and to the bonus fire damage separately.
The Sacred Star: Dawnburst Strike Three Dawnburst Strike: Deal additional Damage TypesRadiant damage equal to your Proficiency Bonus. On a hit, light erupts around you in a 3m / 10ft area. Enemies in the light must succeed a DC 13 Constitution Saving Throw or be Blinded Blinded. This is a weapon action specific to this weapon. As with all weapon actions, it recharges on a short rest.
Balduran's Giantslayer: Topple the Big Folk Three Deal additional damage equal to your Proficiency Bonus. On a hit, Large, Huge, or Gargantuan creatures take an additional 2d6Damage TypesSlashing damage and must suceed a Strength Saving Throw or fall Prone. This is a weapon action specific to this weapon. As with all weapon actions, it recharges on a short rest.
Crimson Mischief: Redvein Savagery Three (Only when wielded in main hand) When you make an attack with Advantage Icon.png Advantage, the target takes an additional 7Damage TypesPiercing damage. This applies for most damage sources in the base attack, It does not apply on some DRSs eg the ranger colossus slayer ability.
Duelist's Prerogative: Withering Cut Three (Only when wielded in main hand) On a hit with a melee weapon, use a reaction to deal additional Damage TypesNecrotic damage equal to your Proficiency Bonus. N/a
Nyrulna: Zephyr Connection Three Zephyr Connection: This weapon will return to your hand when thrown. You cannot be forced to drop the trident. When thrown, the weapon creates an explosion that deals 3d4Damage TypesThunder damage in a 6m/20ft blast centered on the target. This is only works when thrown.

This damage does not benefit from many damage riders that are applied to the base weapon attack.

Silver Sword of the Astral Plane: Soulbreaker One or Three Soulbreaker: Rend the enemy's body and soul, dealing an additional 4Damage TypesPsychic damage, and possibly Stun Stun them. This is a weapon action specific to this weapon. As with all weapon actions, it recharges on a short rest.
Class Abilities
Class Level

Obtained

Relevant Effect Notes
Rogue Rogue 1 Sneak Attack Sneak Attack: Deal an extra 1d6 damage to a foe you have Advantage against. You can also use Sneak Attack if you have an ally within 1.5m / 5ft of the target and you don't have Disadvantage. Sneak Attack is only treated as a damage source if you use the automatic reaction. Using the Sneak Attack action is instead treated as a damage rider.
Paladin Paladin 2 Divine Smite Divine Smite: Your weapon emanates divine might as you strike, dealing an additional 2d8Damage TypesRadiant damage. Deals an additional 1d8Damage TypesRadiant damage to Fiends and Undead. N/a
Hunter Hunter 3 Colossus Slayer Colossus Slayer: Once per turn, your weapon attack deals an extra 1d8Damage TypesPhysical damage if the target is below its hit point maximum This can be applied multiple times for each damage source in the portion of the attack that triggers it. This could include the entire attack or just portions of it.
Cleric Cleric 8 Divine Strike Divine Strike: Once per turn, deal 1d8 damage (damage type depends on Cleric Domain) in addition to your weapon's damage. The 1d8Damage TypesPhysical variant from War Domain War Domain is treated as a damage source only when triggered as a reaction. All other variants of Divine Strike Divine Strike work as damage sources either when used as a reaction or when used directly.
Way of Shadow Way of Shadow 11 Shadow Strike Shadow Strike: Teleport to a foe from a hidden position, striking them with the creeping, psychic ferocity of the shadows themselves, dealing an additional 3d8Damage TypesPsychic damage. N/a
Warlock Warlock 12 Lifedrinker Lifedrinker: Your melee attacks deal additional Necrotic equal to your Charisma modifier. N/a
Spells
Ability Ability Type Relevant Effect Notes
Eldritch Blast Eldritch Blast Cantrip Conjure a beam of crackling energy. Deals 1d10Damage TypesForce damage to a target. This cantrip fires an additional beam at level 5 and 10. Has a damage source per beam fired.
Ensnaring Strike (Melee) Ensnaring Strike (Melee) and Ensnaring Strike (Ranged) Ensnaring Strike (Ranged) 1st Level Spell Your attack summons thorny vines, dealing Weapon Damage and possibly Ensnaring Ensnaring your target.

Ensnared creatures cannot move and take 1d6Damage TypesPiercing damage at the start of each turn. An ally can use their Help Action to try and tear away the vines.

Ensnaring Strike allows spell based bonus damage to ride along with weapon based damage riders as sources. Most damage riders do not apply to the ongoing damage.
Hail of Thorns Hail of Thorns 1st Level Spell Shoot a volley of thorns. They deal weapon damageDamage TypesPhysical and explode, dealing an additional 1d10Damage TypesPiercing damage to the target and surrounding creatures. The initial hit and explosion are separate damage sources.
Hunter's Mark Hunter's Mark 1st Level Spell Mark a creature as your quarry to deal an additional 1d6Damage TypesPhysical damage whenever you hit it with a weapon attack. Only when used with thrown weapon attacks.
Ice Knife Ice Knife 1st Level Spell Throw a shard of ice that deals 1d10Damage TypesPiercing damage. It explodes and deals 2d6Damage TypesCold damage to anyone nearby. It leaves an Ice Surface. On miss, the shard of ice still explodes. The Piercing and Cold Damage are separate damage sources.
Magic Missile Magic Missile 1st Level Spell Create three darts of magical force, each dealing 1d4 + 1Damage TypesForce damage to its target. The darts always hit their target, and can each be targeted individually. Each dart fired is a separate damage sources.
Searing Smite Searing Smite 1st Level Spell Your weapon flares with white-hot intensity. It deals, on top of weapon damage, an extra 1d6Damage TypesFire damage and marks the target with Searing Smite Searing Smite.

A target with Searing Smite takes 1d6Damage TypesFire damage every turn, until it succeeds on a Constitution Saving throw.

The weapon damage and extra fire damage are separate damage sources. Searing Smite allows spell based bonus damage to ride along with weapon based damage riders as sources. Most damage riders do not apply to the ongoing damage.
Thunderous Smite Thunderous Smite 1st Level Spell Your weapon rings with thunder as you strike, pushing your target 3 m / 10 ft away and possibly knocking them Prone Prone. In addition, your weapon deals an additional 2d6Damage TypesThunder damage. The weapon damage and extra thunder damage are separate damage sources. Thunderous Smite allows spell based bonus damage to ride along with weapon based damage riders as sources.
Witch Bolt Witch Bolt 1st Level Spell Link yourself to a target with a bolt of lightning. Deal an additional 1d12Damage TypesLightning each turn by activating it. The additional activations apply most damage riders and are a separate damage source.
Wrathful Smite Wrathful Smite 1st Level Spell Your weapon absorbs your wrath as you strike, possibly Frightening Frightening your target. In addition, your weapon deals an additional 1d6Damage TypesPsychic damage. The weapon damage and extra psychic damage are separate damage sources. Wrathful Smite allows spell based bonus damage to ride along with weapon based damage riders as sources.
Branding Smite Branding Smite 2nd Level Spell Your weapon gleams with astral radiance as you strike and possibly mark your targets with light, preventing it from turning Invisible Invisible. In addition, your weapon deals an additional 2d6Damage TypesRadiant damage. The weapon damage and extra radiant damage are separate damage sources. Branding Smite allows spell based bonus damage to ride along with weapon based damage riders as sources.
Heat Metal Heat Metal 2nd Level Spell Cause a metal Weapon or Armour to glow red-hot and force the creature touching it to let go or receive Disadvantage Icon.png Disadvantage on Attack rolls and Ability Checks. If the creature is only wearing metal armour, it always receives Disadvantage.

If the creature is still touching the metal, you can use a Bonus Action on subsequent turns to Reapply Heat Metal Reapply Heat Metal to deal another 2d8Damage TypesFire damage and force the creature to let go or receive Disadvantage.

The additional activations apply most damage riders and are a separate damage source.
Scorching Ray Scorching Ray 2nd Level Spell Hurl 3 rays of fire. Each ray deals 2d6Damage TypesFire damage. Each ray is a separate damage source.
Blinding Smite Blinding Smite 3rd Level Spell Evoke a heavenly flare and possibly Blind Blind your target. In addition, your weapon deals an additional 3d8Damage TypesRadiant damage. The weapon damage and extra radiant damage are separate damage sources. Blinding Smite allows spell based bonus damage to ride along with weapon based damage riders as sources.
Call Lightning Call Lightning 3rd Level Spell Call down lightning to hit all targets within range and its area of effect for 3d10Damage TypesLightning damage. The additional activations apply most damage riders and are a separate damage source.
Lightning Arrow Lightning Arrow 3rd Level Spell This spell allows spellcasters to fire an arrow of electricity that bursts on impact, dealing additional Lightning damage to creatures in the vicinity. The initial hit and explosion are separate damage sources.
Ice Storm Ice Storm 4th Level Spell Impel a storm of hail and ice to crash from the sky, covering the ground and striking all objects and creatures within range, dealing Damage TypesBludgeoning and Damage TypesCold damage. It also creates an Ice Surface that lasts 2 turns. The Bludgeoning and Cold damage are separate damage sources.
Curriculum of Strategy: Artistry of War Curriculum of Strategy: Artistry of War 5th Level Spell Summon the apparitions of 6 master strategists. Each apparition strikes a target of your choosing, dealing 2d6 + 6Damage TypesForce damage (for a total of 12d6 + 36Damage TypesForce). Each of the six apparitions is a separate damage source.
Destructive Wave Destructive Wave 5th Level Spell Create a shockwave of either divine or malevolent thunder that damages nearby creatures and possibly knocks them Prone Prone. This spell deals 5d6 Damage TypesThunder damage and 5d6 Damage TypesRadiant or 5d6 Damage TypesNecrotic damage. The Thunder and Radiant or Necrotic damage are separate damage sources.
Flame Strike Flame Strike 5th Level Spell This spells allows the caster to make a pillar of divine flame at a chosen location dealing 5d6 Damage TypesFire damage and 5d6 Damage TypesRadiant damage. The Fire and Radiant damage are separate damage sources.
Sunbeam Sunbeam 6th Level Spell This spell allows spellcasters to project a beam of light, Blinding and dealing 6d8 Damage TypesRadiant damage to everything in its path. You can then use Recast Sunbeam Recast Sunbeam on subsequent turns without expending a Spell Slot. The additional activations apply most damage riders and are a separate damage source.

Technical details

The scripts defining all the effects in the game are found in .txt files inside Gustav.pak and Shared.pak. (See Modding:Unpacking and converting files). In these scripts, damage rider effects are implemented with one of several damage functions. These are:

  • WeaponDamage(), CharacterWeaponDamage(), and CharacterUnarmedDamage():
    The basic, well-behaved damage bonuses are implemented with this function. The bonus will apply only to the triggering attack, and nothing else.
    Example effect: 2Damage TypesAcid from Caustic Band.
  • DamageBonus():
    Damage riders using this function will apply their bonus damage to each independent damage instance. When combined with damage riders using DealDamage() (see below), a single attack can create numerous independent damage instances. In these cases, DamageBonus() will apply its bonus damage multiple times, but WeaponDamage() only once.
    Example effect: 2Damage TypesRadiant from Callous Glow Ring.
  • DealDamage():
    This function is used by all damaging attacks, spells, and status effects to apply their damage. It is also used by "damage riders treated as damage sources" to apply their bonus damage. It creates a separate damage instance that can be independently boosted by applicable DamageBonus() effects. Furthermore, damage riders using DealDamage() can trigger each other in some cases, creating far more damage instances than might be expected.
    Example effect: 1d8Damage TypesPhysical from Colossus Slayer.

Each of these functions can optionally specify the damage type. If not specified, the damage type will be inherited from the triggering DealDamage() instance.

Potential bugs

The following items compose a non-exhaustive list which indicates that the "Damage Riders" as compared to "Damage Riders treated as Damage Sources" may include several bugs and therefore many of these abilities may change in future patches:

  • Patch 3 changed Lightning Charges from a "Damage Rider treated as a Damage Source" to a "Damage Rider."
  • Patch 5's patch-notes mention a change to Tavern Brawler in regards to thrown weapons, likely intending to change it from a "Damage Rider treated as a Damage Source" to a "Damage Rider" - in fact no change was made. Instead, Dwarven Thrower, Lightning Jabber, and Hunter's Mark were updated in a comparable manner, leaving them still able to trigger certain other DRS-effects while not applying Damage Riders themselves.
  • Sneak Attack is treated as a Damage Rider when a character uses the Sneak Attack action, but as a "Damage Rider treated as a Damage Source" when Sneak Attack is applied by the automatic reaction system.