Do Two Class Features That Add The Same Modifier to Damage Double It?

Question

I've had a question that I can't seem to find an answer to and it's hard to formulate a question that I feel is clear enough without explaining the setup.

Lets use a 6/2 Sorc/Warlock as an example. Say the Warlock took the Undying Light patron from the Unearthed Arcana - Underdark supplement. Their 1st level feature Radiant Soul allows them to add their Charisma modifier to any radiant or fire damage they do. Next, they take the Red Dragon Draconic Bloodline for their sorcerer levels. At 6th level, they get to add their Charisma modifier to any fire damage they do. Lets say their Charisma is 16 (+3).

Does this mean any fire spell they cast will have double their Charisma damage (+6)? I can't find answers to say one way or another since it's an added feature from two different classes.

Example: this character would cast a Firebolt that deals 2d10+6 fire damage on a hit.

I assume yes, considering if it was a Tempest Cleric and Blue Dragon Sorc, you would add Wisdom and Charisma to your lightning spells and I see nothing wrong with that.

Answer 1

Yes, these 2 effects will stack. There is a rule to prevent stacking the proficiency bonus from being stacked on a roll, and there is a rule that says you can't benefit from 2 of the same spell simultaneously, but these are the only rules that restrict bonus stacking.

The most concrete example we have of stacking an ability modifier is the Paladin's Aura of Protection, which Crawford, lead designer of 5e, has confirmed allows them to add their Charisma modifier twice to Charisma saving throws - once because, well, it's a Charisma saving throw, and once from Aura of Protection.

Another example of identical effect stacking is benefiting from multiple Auras of Protection, where Crawford confirmed that you can benefit from identical effects as long as they aren't spells. Twice.

Answer 2

Yes; the DMG-Errata supports the stacking of these two effects

Chapter 8 Combining Game Effects (p. 252).
This is a new subsection > at the end of the “Combat” section: Different game features can affect a target at the same time. But when two or more game features have the same name, only the effects of one of them—the most potent one—apply while the durations of the effects overlap. For example, if a target is ignited by a fire elemental’s Fire Form trait, the ongoing fire damage doesn’t increase if the burning target is subjected to that trait again. Game features include spells, class features, feats, racial traits, monster abilities, and magic items. See the related rule in the “Combining Magical Effects” section of chapter 10 in the Player’s Handbook. {Italics added}

What is a game element? Is it a spell or a feat or a class/race feature, or is it an effect granted by this? The example given is that the same trait of different creatures does not stack, not that any feature that also does burning damage but with another name does not stack.

The cited Twitter/Tweet above also mentioned that you can stack multiple "flat" bonuses. If the effect would be the game feature, than having a ring of protection and the shield spell would not stack, or having shield of fate and shield spell. But we know that those do stack.

As the feature = effect is not true (chapter 10 combining magical effects) means that yes you stack agonizing blast and radiant soul.

Answer 3

Pg 3, "Light, Dark, Underdark" Unearthed Arcana

Radiant Soul

... when you cast a spell that deals radiant damage or fire damage, you add your Charisma modifier to that damage.

PHB, pg 102

Elemental Affinity

... when you cast a spell that deals damage of the type associated with your draconic ancestry, add your Charisma modifier to that damage.

Each of these enable you to add your Charisma modifier to the damage. The question is: if you have both is one simply irrelevant or do you add your Charisma bonus twice?

The rules do not say.

Personally, I would rule that it is not added twice because:

1. The precedent with the proficiency bonus is that it can never be added more than once (p.12). While it can be doubled this is specifically called out as a doubling, which is not what is going on here.
2. There are precedents for adding different ability bonuses (e.g. the monk's unarmoured defence), however, there is none for adding the same ability bonus more than once.
3. It is analogous to the Combining Magical Effects (p. 205).
4. The effects allow you to apply your presence in the form of your charisma bonus to the damage. I would need some convincing that your radiant soul and draconic ancestry combined to allow you to be twice as good at that.

Answer 4

The relevant rules:

Radiant Soul

...when you cast a spell that deals radiant damage or fire damage, you add your Charisma modifier to that damage.

and

ELEMENTAL AFFINITY

...when you cast a spell that deals damage of the type associated with your draconic ancestry, add your Charisma modifier to that damage.

In this case the OP is choosing Red Dragon ancestry so the Elemental Affinity applies to fire damage.

I would say the answer is 'no' based on a narrow interpretation of the rules. You either add the modifier or you don't, the number of effects that allow you to is irrelevant.

I base this on the clear split between classes that use weapons and those that use magic. Weapon users always get to add their key ability modifier to damage rolls, and casters by default never do. The purpose of these class features and others like them seems to be to allow a caster to sometimes benefit from a high key ability modifier.

I can't speak to designer intent, but there is a clear pattern that this kind of damage modifier only gets added once per hit. Even on a critical hit where the dice are doubled you still only add the modifier once. The Two-Weapon Fighting Style class feature lets Fighters and Rangers add theirs twice -- on separate attacks (and if they take the Duelist style, it's a flat +2 damage bonus, rather than double the ability modifier).

It's no accident that you can't multiclass Fighter/Barbarian or Rogue/Monk to double your Strength or Dexterity bonus to damage. It's also no accident that this particular combination only arises from multiclassing, and only from the "highly volatile" and "unstable" Unearthed Arcana rules. If the intent was that the bonus could be doubled, I'd expect that there would at least be one combination of class features within the same class that would allow it.

I don't know about the Tempest Cleric, but the Knowledge Cleric has a feature that let's them add their Wisdom modifier to some damage rolls, and if someone wanted to build a cleric/sorcerer or cleric/warlock so they could add both their Wisdom and Charisma, that would be different: they'd have a domain that is otherwise fairly weak in combat, they'd have to get to Cleric level 8, and they wouldn't get the maximum benefit until they had maxed out two abilities (level 16 at the earliest with the standard array and races I believe). It would be a nice reward for a character concept that took significant investment and sacrifice.

Answer 5

Yes they add their bonuses to fire damage, there is no "stacking"

Combining Magical Effects (page 205, PHB)

The effects of different spells add together while the durations of those spells overlap. The effects of the same spell cast multiple times don't combine, however. Instead, the most potent effect—such as the highest bonus—from those castings applies while their durations overlap. For example, if two clerics cast bless on the same target, that character gains the spell’s benefit only once; he or she doesn’t get to roll two bonus dice

(Emphasis mine)

RADIANT SOUL -- ELEMENTAL AFFINITY

These are two separate abilities with different names. So even if we extrapolate this rule out to affect Magical Abilities instead of just spells, these two abilities have different names which means they are different abilities and therefor they are not violating the combining magical effect rules. The charisma bonus is just how you determine the bonus the ability provides.

Answer 6

Bonuses (+X) always stack. Things that double, halve, replace, or negate numbers have special rules, none of which have anything to do with this particular case.

Answer 7

Yes, you would add your charisma modifier twice to the spell.

Answer 8

Maybe not, but it's unclear

The only interaction between multiple ability modifiers that I can recall at the moment is Unarmored Defense. Namely: The Barbarian and Monk's Unarmored Defense do not stack.

Additionally, because both abilities say "add your Charisma modifier to that damage", I would say no. It's not "Add a number equal to your CHA mod" it's "add your CHA mod".

Given this evidence, I would tend to say no, you cannot add it twice. However, it is unclear, and this is definitely a RAI interpretation at best.

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That being said, I can definitely see how damage rolls are very different than AC, so it could very well be that it's fine to do. I think if you can add two different ability modifiers to a damage roll, then there should be no reason you can't add the same one twice. The difference will be fairly small. Your example has an 8th level character gaining an extra +3 to +4 damage per round. When your dealing ~36 damage in a single round, +/- 10% isn't a huge deal.

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This sounds like a good question to ask the game devs on twitter tho.

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Pg 3, "Light, Dark, Underdark" Unearthed Arcana

Radiant Soul

Starting at 1st level, your link to the Positive Plane allows you to serve as a conduit for radiant energy. You have resistance to radiant damage, and when you cast a spell that deals radiant damage or fire damage, you add your Charisma modifier to that damage. Additionally, you know the sacred flame and light cantrips and can cast them at will. They don’t count against your number of cantrips known.

PHB, pg 102

ELEMENTAL AFFINITY

Starting at 6th level, when you cast a spell that deals damage of the type associated with your draconic ancestry, add your Charisma modifier to that damage. At the same time, you can spend 1 sorcery point to gain resistance to that damage type for 1 hour.