I've a couple of questions regarding stacking multiple area effect spells:

  1. Does Celestial Brilliance spell (BoED p94) stack with itself? That is, if two instances of this spell are cast and an evil outsider is within both areas of effect, does it take 4d6 points of damage or 2d6? Why? (there are plenty of spells like that, e.g. wall of fire, it's just Celestial Brilliance which is easy to stack)

  2. What if it was an emanation, instead of an unspecified area effect?

  3. What if it was a spread?

  • \$\begingroup\$ As a DM, I would break out the most resounding "NO" I had in my bag of tricks, answers, but at first glance I can't find a rule that allows or disallows it either way. \$\endgroup\$
    – dpatchery
    Commented Jul 5, 2011 at 14:35
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    \$\begingroup\$ I think the part that says "different strength spells only use the best version" covers it. \$\endgroup\$
    – Cthos
    Commented Jul 5, 2011 at 14:38
  • \$\begingroup\$ @Cthos yep, definitely. Good find. \$\endgroup\$
    – dpatchery
    Commented Jul 5, 2011 at 14:40

2 Answers 2


They would not stack

It's covered by this sentence:

In most cases, modifiers to a given check or roll stack (combine for a cumulative effect) if they come from different sources and have different types (or no type at all), but do not stack if they have the same type or come from the same source (such as the same spell cast twice in succession). If the modifiers to a particular roll do not stack, only the best bonus and worst penalty applies. Dodge bonuses and circumstance bonuses however, do stack with one another unless otherwise specified.

Emphasis mine.

Note, that this is referring to Bonuses, but I believe the same applies to Damage as well, unless the spell says it stacks, it wouldn't stack.

Similar Reference in the Magic Section:

In cases when two or more identical spells are operating in the same area or on the same target, but at different strengths, only the best one applies.

Which I think covers the damage stacking aspect.

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    \$\begingroup\$ +1 The second quotation is what seals it. Note that the rule applies for all scenarios 1, 2 and 3 in the question. The type of area of effect has no influence on the stacking rules. \$\endgroup\$
    – dpatchery
    Commented Jul 5, 2011 at 14:43
  • \$\begingroup\$ Thanks, your second quote is what I've overlooked. (being theoretical now) Still, since the damage is rolled anew each round, is it rolled twice and the larger applied? Or we should use Same Effect with Differing Results section rule here and apply only one instance of the spell? Or both spells have similar effects with similar (2d6) strength and, once again, only one of them applies? \$\endgroup\$ Commented Jul 5, 2011 at 15:50
  • \$\begingroup\$ @Jeor I would say you would only roll it once. I've always read it as since they have similar effects only the stronger (pre calculation) applies. So you'd apply the "similar effect" rule before rolling. And since they're both 2d6, only 2d6 would ever get rolled. \$\endgroup\$
    – Cthos
    Commented Jul 5, 2011 at 16:30

Damage stacks. Bonuses and penalties or similar usually do not: SRD on Casting Spells

Spells that provide bonuses or penalties on attack rolls, damage rolls, saving throws, and other attributes usually do not stack with themselves. More generally, two bonuses of the same type don’t stack even if they come from different spells (or from effects other than spells; see Bonus Types, above).

Different Bonus Names : The bonuses or penalties from two different spells stack if the modifiers are of different types. A bonus that isn’t named stacks with any bonus.

Same Effect More than Once in Different Strengths : In cases when two or more identical spells are operating in the same area or on the same target, but at different strengths, only the best one applies.

Same Effect with Differing Results : The same spell can sometimes produce varying effects if applied to the same recipient more than once. Usually the last spell in the series trumps the others. None of the previous spells are actually removed or dispelled, but their effects become irrelevant while the final spell in the series lasts.

It's pretty clear that whole section deals with bonuses and penalties and not pure damage (even if they affect damage rolls of other attacks, they are not damage spells themselves).
It's also pretty neat for instance to imagine an enemy sandwiched between two Walls of Fire and a Blistering Radiance (or two) cast on top of him. They all do fire damage so same effect, but they should all apply damage normally. There's no reason not to stack.

I'll go even further and say that overlapping area spells do stack all their effects. What I mean is if an area has 2 spells that Slow entering creatures and a creature enters, he has to make two saves, one against each spell. If he fails both saves he still only gets movement halved, not quartered. The Slow effect on him is not stacked. However if dispel is cast on him it has to dispel both spells/effects to "cure" him. This view is supported by logic of Same Effect with Differing Results ("None of the previous spells are actually removed or dispelled") and the section on Charm stacking:

Multiple Mental Control Effects : Sometimes magical effects that establish mental control render each other irrelevant, such as a spell that removes the subjects ability to act. Mental controls that don’t remove the recipient’s ability to act usually do not interfere with each other. If a creature is under the mental control of two or more creatures, it tends to obey each to the best of its ability, and to the extent of the control each effect allows. If the controlled creature receives conflicting orders simultaneously, the competing controllers must make opposed Charisma checks to determine which one the creature obeys.

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    \$\begingroup\$ @Cthos quotes a section from the SRD that cuts the PH examples that show the effect is important, not the bonuses, penalties, or even damage, and multiple celestial brilliance spells create effects that don't stack because they're essentially the same source. That the effect deals damage is of secondary concern. Likewise, for comparison, two overlapping walls of fire don't deal a dude running through them twice as much damage, but if the dude ran through two separate walls of fire, he'd be dealt damage twice. \$\endgroup\$ Commented Sep 22, 2016 at 20:48
  • \$\begingroup\$ do you mean on page 172 PHB? i don't see examples there with damage spells \$\endgroup\$
    – Simanos
    Commented Sep 22, 2016 at 21:41
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    \$\begingroup\$ I know! That's what I mean. Let me take this further: the spell celestial brilliance is pretty much, just a bigger, badder light spell (even targeting an object). Two overlapping light spells don't make the overlapping part even brighter; likewise, two overlapping celestial brilliances don't deal more damage. The effect is even called out as dealing damage on the affected creature's clock rather than caster's. \$\endgroup\$ Commented Sep 22, 2016 at 21:58
  • \$\begingroup\$ my point is there are no examples with damage roles because the authors assume damage always stacks, only other effects do not stack, but if you're affected by two charm spells, the effect does not stack but needs two rolls to dispel. Like if you cast a spell that makes an area slow people twice, people will have to roll two saves when they enter the area. They just will not have been slowed twice (1/4th) if they fail both saves. \$\endgroup\$
    – Simanos
    Commented Sep 22, 2016 at 23:04
  • \$\begingroup\$ what i mean is, the effects do not stack, but the area spells do, i should add this to my answer if i can figure an elegant way of saying it \$\endgroup\$
    – Simanos
    Commented Sep 22, 2016 at 23:05

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