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 vs. Damage Riders

A damage source could be described as what initializes the damage. Examples include striking a target with your weapon, a spell, or thrown items such as an Alchemist's Fire. Damage sources often 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 spell).

A damage rider is something which adds additional damage onto the damage source. It can only be present in the event there is an applicable damage source for it to "ride along" with, hence the name of a damage rider. Examples of damage riders include the Hex spell adding damage to the damage from a Warlock's eldritch blast or weapon attacks, coatings applied to weapons providing additional damage to a weapon attack, a 6th level  Draconic Bloodline applying their elemental affinity to a spell of the appropriate damage type, or a raging 25 adding rage damage to their weapon attacks. Many damage riders are gained from passives from buffs. Any eligible damage riders from a damaging will be applied to a damage source which is a part of that damaging effect.

Damage Riders treated as Damage Sources

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.

Example Calculation

A character with 18 Strength, the Tavern Brawler Feat, Lightning Charges, and the Ring of Flinging uses the Returning Pike to make a thrown weapon attack against a target which is affected by Hex.

Damage Sources:

• Thrown weapon attack using the Returning Pike applies 1d10 (damage die) + 1 (weapon enchantment) + 4 (Strength modifier) piercing damage

Damage Riders:

• Lightning Charges 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 adds 1d6 necrotic damage to each damage source.

Damage Riders treated as Damage Sources:

• The Tavern Brawler feat allows characters to add their Strength modifier an additional time to damage rolls when using unarmed strikes, improvised weapons, or thrown weapons. When applied to melee attacks this damage bonus is treated as a damage rider. But as of Patch 3 with thrown weapons, this +4 piercing damage from the character's strength score being applied a second time due to the tavern brawler feat being treated as a damage source.

Calculating total damage:

To determine the total damage applied take each "damage source" and "damage rider treated as a damage source". Then apply the damage riders onto each of these. In this example that means one should evaluate the pike damage source plus all damage riders, followed by the Tavern Brawler damage source and all damage riders applied again.

Tavern Brawler on thrown weapon attacks is a Damage Rider which is treated as a Damage Source, meaning the damage roll in the above scenario would on average yield 28.5 total damage (ignoring resistances) calculated as follows:

* 1d10 (5.5 avg) (weapon damage die) + 1 (weapon enchantment) + 4 (Strength modifier) Piercing from the Returning Pike thrown weapon attack, [Damage Source]
** +1d4 (2.5 avg) Piercing damage from the Ring of Flinging, [Damage Rider]
** +1 Lightning damage from Lightning Charges, [Damage Rider]
** +1d6 (3.5) Necrotic damage from Hex, [Damage Rider]

* +4 Piercing damage from Tavern Brawler, [Damage Rider treated as Damage Source]
** +1d4 (2.5 avg) Piercing damage from the Ring of Flinging being applied to Tavern Brawler damage source, [Damage Rider]
** +1 Lightning damage from Lightning Charges being applied to Tavern Brawler damage source, [Damage Rider]
** +1d6 (3.5 avg) Necrotic damage from Hex being applied to Tavern Brawler damage source [Damage Rider]

As a hypothetical scenario to show the impact that this minor detail can have, instead imagine Tavern Brawler were to be treated as a damage rider in the above scenairo. In this hypothetical scenario the above damage roll would yield 21.5 total damage on average (ignoring resistances) calculated as follows:

* 1d10 (5.5 avg) (weapon damage die) + 1 (weapon enchantment) + 4 (Strength modifier) Piercing damage from the Returning Pike weapon attack, [Damage Source]
** +1d4 (2.5 avg) Piercing damage from the Ring of Flinging, [Damage Rider]
** +1 Lightning damage from Lightning Charges, [Damage Rider]
** +1d6 (3.5) Necrotic damage from Hex, [Damage Rider]
** +4 Piercing damage from Tavern Brawler, [If Tavern Brawler were to hypothetically be treated as a damage rider with thrown weapon attacks]

Effects which apply "Damage Riders"

Weapons and Equipment

Item	Relevant Effect	Notes
Callous Glow Ring	The wearer deals an additional 2Radiant damage against creatures that are illuminated	N/a

Abilities

Class	Subclass	Level Obtained	Relevant Effect	Notes
Rogue	N/a	1	Sneak AttackDeal 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 a damage rider if you use the Sneak Attack Action. Using the automatic Sneak Attack reaction is instead a "Damage Rider Treated as a Damage Source."
Sorcerer	Draconic Bloodline	6	Elemental Affinity: DamageWhen you cast a spell that deals damage of the type associated with your draconic ancestry, you add your Charisma modifier to the damage.	N/a

Spells

Spell	Spell Level	Relevant Effect	Notes
Hex	1	Make your attacks deal an additional 1d6Necrotic damage [sic] to the target...	N/a

Miscellaneous

Spell	Relevant Effect	Notes
Lightning Charges	Lightning courses through you. You have +1 to Attack Rolls and deal an additional 1Lightning damage. If you gain 5 charges, they are consumed the next time you deal damage, and you deal an additional 1d8Lightning damage.	Lightning Charges were "Damage Riders treated as Damage Sources" until Patch 3

Effects which apply "Damage Riders treated as Damage Sources"

Weapons and Equipment

Item	Relevant Effect	Notes
Phalar Aluve: Shriek	All enemies within 6m of range have a 1d4 penalty to Charisma, Wisdom and Intelligence Saving Throws. Affected creatures receive an extra 1d4Thunder damage. The sword will stop Shrieking if unequipped.	N/a

Abilities

Class	Subclass	Level Obtained	Relevant Effect	Notes
Rogue	N/a	1	Sneak AttackDeal 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 automatic Sneak Attack action is instead treated as a damage rider.

Spells

Spell	Spell Level	Relevant Effect	Notes
Hunter's Mark	1	Mark a creature as your quarry to deal an additional 1d6Physical damage whenever you hit it with a weapon attack.	N/a

Miscellaneous

Spell	Relevant Effect	Notes
Tavern Brawler Feat	When you make an unarmed attack, use an improvised weapon, or throw something, your strength modifier is added twice to the damage and Attack Roll	N/a

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."
• Tavern Brawler is treated as a Damage Rider with unarmed attacks and improvised weapon attacks, but as a "Damage Rider treated as a Damage Source" when it comes to thrown weapon attacks.
• 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.