D&D 5E Combining Magical Effects

[Giant2005]

Here is the actual rule in question:

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.

Now it is pretty clear that rule was made in order to prevent buff and debuff stacking, but how does it interact with two instances of spells like Spirit Guardians or Flaming Sphere? At the end of a creatures turn, if it is in range of two Flaming Spheres, does it take damage from both or just one?
So how do you think that rule works regarding damage spells RAW, RAI, and how would you rule it personally?

 

[CapnZapp]

Just like two Fireballs deal twice as much damage as one Fireball, two Spiritual Weapons deal twice as much as one.

On the other hand, two Cloud of Daggers or two Insect Plagues or two Evard's Black tentacles doesn't create an area twice as dangerous as one. Edit: This applies to Flaming Sphere too, since it doesn't deal direct damage but only creates an area.

Direct damage always stacks. Other effects doesnt.

Two Slow doesn't slow you any more than one. Two Sleep doesn't make you sleep any harder than one. Two Fear doesn't affect you more than one.

 

[CapnZapp]

Now it is pretty clear that rule was made in order to prevent buff and debuff stacking, but how does it interact with two instances of spells like Spirit Guardians or Flaming Sphere? At the end of a creatures turn, if it is in range of two Flaming Spheres, does it take damage from both or just one?
So how do you think that rule works regarding damage spells RAW, RAI, and how would you rule it personally?

Two instances of Spirit Guardians can create a larger effect (area) than one. That's the only benefit.

The joint area covered by two Spirit Guardians is not more dangerous or difficult to traverse than one. No double damage. No two saves. No two halvings of the speed.

Edit: the same applies to Flaming Sphere. I first mistakenly thought you used the sphere to attack, much like a Spiritual Weapon. You don't - the sphere is technically treated as an area, and two instances of the same spell doesn't stack: two Flaming Spheres can't stack to create a 4d6 area.

You would, however, be within your rights to ask for the 2d6 to be rolled twice, so you could pick the greatest damage. (If the Flaming Sphere of Bob is DC 15 and causes 6 points of damage and the Flaming Sphere of Sue is DC 14 and causes 8 points of damage, Joe the Goblin makes one DC 15 save and, upon failure, takes 8 points of damage for standing in the area covered by both spheres)

Spiritual Weapon (or Fireball etc) doesn't need to stack to cause double damage. And so they cause double damage.

 

[CapnZapp]

So how do you think that rule works regarding damage spells RAW, RAI, and how would you rule it personally?

My answers above cover how I think the rule works RAW, RAI, RAF and HIWRIP

 

[Plaguescarred]

how does it interact with two instances of spells like Spirit Guardians or Flaming Sphere? At the end of a creatures turn, if it is in range of two Flaming Spheres, does it take damage from both or just one?

Only once i believe since only the most potent effect of the same spell cast multiple times apply while overlapping. So multiple flaming sphere shouldn't make their overlapping area any more hot than a single one is for exemple.

 

[UngeheuerLich]

I think the errata document has the text for stacking game effects in general. One example is a fire aura and they don't stack. The stronger one deals damage. On the other hand I maybe overrule that and make the strongest one deal full damage and every other half.
But then I am a very lazy DM and don't fix anything that does not seem broken in actual play. But I usually have some ideas to balance something just in case.

 

[Plaguescarred]

Yes the DMG Errata says;

Combining Game Effects (p. 252). This is a new subsection atthe 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 issubjected 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

 

[CapnZapp]

TBH I view that errata not as a genuine change, but more of an "oops we forgot to add the rule from the PHB into the DMG" moment.

 

[CapnZapp]

The thing is, they still fail to provide the truly deciding and useful example.

Such as my Flaming Sphere example above.

The tricky part is how to judge "most potent one". What does "potent" mean. We get no definition, so we have only natural language.

In my example above, I decided to go with the most generous intepretation, where the goblin needs to save versus the hardest DC and is subject to the most damage, even when they originate with different castings.

In this way, while castings of the same spell doesn't stack, they "cooperate".

---

However.

I can definitely see a DM deciding to go with one or the other, but not with this amalgam of both. Perhaps for simplicity, or perhaps because the rules never say anything about amalgamating two castings.

So if your DM decides to simply say "the casting with the most damage is the one to use" that can't be contested - it's a very reasonable interpretation of the rule.

If your DM decides to instead say "the casting with the highest save DC is the one to use" that's also difficult to argue with.

Of course, your DM could go even further, and simply say something like "additional castings doesn't count". While indeed very simple and fast to use, it will have to remain a ruling rather than a strict interpretation of RAW, since it ignores the "use the potent" clause.

 

[Plaguescarred]

Well the errata clarify that when two or more same-named spell overlap, only the effects of one of them—the most potent one—apply while the durations of the effects overlap. In the case of 2d6 fire damage (save for half) only one of them means that it doesn't really matter if you use the first or second casting, only one spell will have an effect.