Damage mechanics

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 . 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 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 spell adding damage to the damage from a Warlock's or weapon attacks, coatings applied to weapons providing additional damage to a weapon attack, a 6th level applying their elemental affinity to a spell of the appropriate damage type, or a raging 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, , and the uses the to make a thrown weapon attack against a target which is affected by .
Damage Sources (DS):
*Thrown weapon attack using the applies 1d6 (damage die) + 1 (weapon enchantment) + 5 (Strength modifier) piercing damage
Damage Riders (DR):
* add +1 Lightning Damage to each damage source
*The adds 1d4 damage which is of the same type as the weapon used (piercing in this example) to each damage source.
* 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 's passive, Throwing: Lightning Damage, 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 with all damage riders applied again. 
Treating the bonus lighting damage from throwing the as DRS' means the damage roll in the above scenario would on average yield 36 total damage (ignoring resistances) calculated as follows:
* from the thrown weapon attack, [DS]
** damage from the , [DR]
** from , [DR]
** damage from , [DR]
** damage from Tavern Brawler on a character with 20 Strength, [DR]
* damage from the bonus effect of throwing the , [DRS]
** damage from the , [DR]
** from , [DR]
** damage from , [DR]
** damage from Tavern Brawler on a character with 20 Strength, [DR]
As a hypothetical scenario to show the impact that this minor detail can have, instead imagine the bonus lighting damage from throwing the 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:
* from the thrown weapon attack, [DS]
** damage from the , [DR]
** from , [DR]
** damage from , [DR]
** damage from Tavern Brawler on a character with 20 Strength, [DR]
** damage from the bonus effect of throwing the in the hypothetical scenario where it is treated as a traditional damage rider [DR]
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
 	All 	Deals Weapon Damage + (Dexterity Save to negate). Creates a permanent Surface. 	N/a
 	All 	Deals weapon damage + (Dexterity Save to negate). Creates a Surface for 2 turns. 	N/a
 	All 	Deals weapon damage + (Dexterity Save to negate). Creates an for 2 turns. 	N/a
 	All 	Deals weapon damage + (Dexterity Save to negate). 	N/a
 	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
 	One 	Deathly Slumber: Deals an additional 1d4 damage to creatures that are   or . 	N/a
 	One 	Inflicts Shattered on hit. When attacking a Shattered target, deal an additional damage. 	N/a
 	One 	Deals an additional damage to targets. 	Can apply multiple times.
 	One 	Deals an additional damage to Plants, Insects or Small creatures. 	N/a
 	One 	Deals an additional damage to targets. 	Can apply multiple times.
 	One 	Revitalising Strike: Smash into a foe, wounding them and healing your own injuries. On a hit, heal . You deal additional   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.
 	One 	Willing Whip: Grants Resistance to damage. Deals an additional 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.
 	One 	Blood Sacrifice: Pain is a path to power. Take damage to receive a +1d4 bonus to Attack Rolls and Saving Throws. 	Damage riders are applied to the self inflicted damage.
 	One 	Break the Unbroken: Deal an additional damage to targets that still have all their hitpoints. 	The target must be at full health. Only applies to attacks made with the weapon itself.
 	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 Lightning damage equal to your remaining . 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.
 	One or Two 	Gargantuan Cleave: Swing your weapon with all your might. You can attack multiple targets, but become . 	This is a weapon action specific to this weapon. As with all weapon actions, it recharges on a short rest.
 	One 	When the wielder has 50% or less, they deal an additional damage. 	N/a
 	One 	All enemies within 6m of range have a 1d4 penalty to Charisma, Wisdom and Intelligence Saving Throws. Affected creatures receive an extra 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.
 	One 	Soulbreaker: Rend the enemy's body and soul, dealing an additional damage, and possibly them. 	This is a weapon action specific to this weapon. As with all weapon actions, it recharges on a short rest.
 	Two 	Throwing: Lighting Damage: When launched at a target, deal an additional damage. 	This is only works when thrown.
 	Two 	When the wielder attacks with , they deal an additional damage 	Only applies to attacks made with the weapon itself.
 	Two 	Unnamed ability adds to all regular attacks 	DRS deals damage despite base weapon dealing
 	Two 	Moonlight Butterflies: Strike a foe, conjuring an illusory swarm of moon-pale butterflies, gaining on attacks against the target. Deal additional damage equal to your Proficiency Bonus. When the target moves away from your illusion, it takes damage.	This is a weapon action specific to this weapon. As with all weapon actions, it recharges on a short rest.
 	Two 	Tippler's Rage: When you have the condition, you have on Attack Rolls. You also create a blast with each attack, dealing 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.
 	Two 	Shadowsoaked Blow: Strike an enemy, adding your Proficiency Bonus to the damage. Moreover, if the attack hits, it also deals an additional 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.
 	Two 	On a Critical Hit, the target takes an extra damage as long as it isn't a construct or an undead. You also gain 10 temporary hit points. 	The Life Stealing Critical passive is coded to only function when Sword of Life Stealing crits, even though the description appears to say it functions off any critical hit.
 	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 damage and possibly it. Undead and Constructs can't . 	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.
 	Three 	Whenever you score a Critical Hit, deal an additional damage. 	N/a
 	Three 	Your   deals an additional damage 	N/a
 	Three 	Hellflame Cleave: Spew hellish flames and strike your foes. On Save: Targets still take half damage. Hellfire ignores Resistance and Immunity to 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.
 	Three 	Dawnburst Strike: Deal additional 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 . 	This is a weapon action specific to this weapon. As with all weapon actions, it recharges on a short rest.
 	Three 	Deal additional damage equal to your Proficiency Bonus. On a hit, Large, Huge, or Gargantuan creatures take an additional 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.
 	Three 	(Only when wielded in main hand) When you make an attack with , the target takes an additional damage. 	This applies for most damage sources in the base attack, It does not apply on some DRSs eg the ranger colossus slayer ability.
 	Three 	(Only when wielded in main hand) On a hit with a melee weapon, use a reaction to deal additional damage equal to your Proficiency Bonus. 	N/a
 	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 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.
 	One or Three	Soulbreaker: Rend the enemy's body and soul, dealing an additional damage, and possibly 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
 	1 	: 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.
 	2 	: Your weapon emanates divine might as you strike, dealing an additional damage. Deals an additional damage to Fiends and Undead. 	N/a
 	3 	: Once per turn, your weapon attack deals an extra 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.
 	8 	: Once per turn, deal 1d8 damage (damage type depends on Cleric Domain) in addition to your weapon's damage. 	The variant from is treated as a damage source only when triggered as a reaction. All other variants of work as damage sources either when used as a reaction or when used directly.
 	11	: Teleport to a foe from a hidden position, striking them with the creeping, psychic ferocity of the shadows themselves, dealing an additional damage. 	N/a
 	12	: Your melee attacks deal additional equal to your Charisma modifier. 	N/a
Spells
Ability	Ability Type 	Relevant Effect 	Notes
 	Cantrip 	Conjure a beam of crackling energy. Deals damage to a target. This cantrip fires an additional beam at level 5 and 10. 	Has a damage source per beam fired.
and 	1st Level Spell	Your attack summons thorny vines, dealing and possibly your target.
Ensnared creatures cannot move and take 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.
 	1st Level Spell	Shoot a volley of thorns. They deal and explode, dealing an additional damage to the target and surrounding creatures. 	The initial hit and explosion are separate damage sources.
 	1st Level Spell	Mark a creature as your quarry to deal an additional damage whenever you hit it with a weapon attack. 	Only when used with thrown weapon attacks.
 	1st Level Spell	Throw a shard of ice that deals damage. It explodes and deals damage to anyone nearby. It leaves an Surface. On miss, the shard of ice still explodes. 	The Piercing and Cold Damage are separate damage sources.
 	1st Level Spell	Create three darts of magical force, each dealing damage to its target. The darts always hit their target, and can each be targeted individually. 	Each dart fired is a separate damage sources.
 	1st Level Spell	Your weapon flares with white-hot intensity. It deals, on top of weapon damage, an extra damage and marks the target with . 
A target with Searing Smite takes damage every turn, until it succeeds on a Constitution .	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.
 	1st Level Spell	Your weapon rings with thunder as you strike, pushing your target away and possibly knocking them . In addition, your weapon deals an additional 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.
 	1st Level Spell	Link yourself to a target with a bolt of lightning. Deal an additional each turn by activating it. 	The additional activations apply most damage riders and are a separate damage source.
 	1st Level Spell	Your weapon absorbs your wrath as you strike, possibly your target. In addition, your weapon deals an additional 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.
 	2nd Level Spell	Your weapon gleams with astral radiance as you strike and possibly mark your targets with light, preventing it from turning . In addition, your weapon deals an additional 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.
 	2nd Level Spell	Cause a metal Weapon or Armour to glow red-hot and force the creature touching it to let go or receive on s 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 to deal another damage and force the creature to let go or receive Disadvantage.	The additional activations apply most damage riders and are a separate damage source.
 	2nd Level Spell	Hurl 3 rays of fire. Each ray deals damage. 	Each ray is a separate damage source.
 	3rd Level Spell	Evoke a heavenly flare and possibly your target. In addition, your weapon deals an additional 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.
 	3rd Level Spell	Call down lightning to hit all targets within range and its area of effect for damage. 	The additional activations apply most damage riders and are a separate damage source.
 	3rd Level Spell	This spell allows spellcasters to fire an arrow of electricity that bursts on impact, dealing additional damage to creatures in the vicinity. 	The initial hit and explosion are separate damage sources.
 	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 and damage. It also creates an Surface that lasts 2 turns.	The Bludgeoning and Cold damage are separate damage sources.
 	5th Level Spell	Summon the apparitions of 6 master strategists. Each apparition strikes a target of your choosing, dealing damage (for a total of ). 	Each of the six apparitions is a separate damage source.
 	5th Level Spell	Create a shockwave of either divine or malevolent thunder that damages nearby creatures and possibly knocks them . This spell deals damage and or damage. 	The Thunder and Radiant or Necrotic damage are separate damage sources.
 	5th Level Spell	This spells allows the caster to make a pillar of divine flame at a chosen location dealing damage and damage. 	The Fire and Radiant damage are separate damage sources.
 	6th Level Spell	This spell allows spellcasters to project a beam of light, Blinding and dealing damage to everything in its path. You can then use 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: 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: 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: 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.
Category:Bugs