D&D 5E Booming Blade seems a bit powerful

[KarinsDad]

Somewhat tangential, but does anyone know what happens when two different instance of the same spell are trying to apply different effects?

If two different casters maintain Enhance Ability on the same target, one for Strength and one for Dexterity, what happens? Assuming they were cast using the same level of spell slot, by casters of equal level and casting ability, then I don't see anything to distinguish one as being more potent than the other. They're boosting different scores, so the choice of which one applies would matter.

If I try to apply a rule based on casting order, I get shenanigans. Saying the first instance takes priority means a target can prevent their self from being affected by a Suggestion or a Geas or Phantasmal Force by having an ally cast a version with a harmless effect. Or cast Bestow Curse on an ally, to give them disadvantage on attacks against the caster, and prevent anyone else from cursing them in the process. Saying the most recently cast instance takes priority fails for basically the same reason: now you can block the effect of another caster's spell by having a harmless version cast. Or you could block an enemy's Enhance Ability buff by boosting a score they don't care about--the spell doesn't say the target must be willing, and it offers no save, so why not cast it balefully?

I'm lead to believe that when the bless example was used, it was because the authors were thinking about spells that operate like bless when they wrote those rules. That is to say, spells of a fixed duration (+- concentration) and where each instance can have a different size but an equivalent kind of effect. In which case, the distinction between which of two equally potent effects wouldn't matter.. you don't have to know which instance of the spell is applying its effect, since you know they're all doing the same thing.

A very good set of questions.

I think the simple ruling on this is:

All versions of all spells affect at all times. Only the exact same effect (or boosted same effect) does not repeat. In that case, only the most potent version works (if same potency, do not take best of 2 rolls). To be the same effect, it has to be the same spell (special abilities by monsters are not spells unless otherwise stated, so multiple similar or same effects are possible).

So, someone could have Geas on them from an ally, but a different Geas from an enemy would also still work. DItto Bestow Curse since disadvantage against two targets would result in two different effects. Enhance Ability for both Str and Dex results in both being boosted.

Two different Suggestions could result in a conflict, so some simple alternating save until one spell is gone might be needed. A spell that results in 100% compulsion like Suggestion needs a way for only one of them to work at a time if and only if they conflict (a Suggestion in a higher level slot would be more potent and hence win in a conflict scenario). The other Suggestion spells duration still exists and if the winning Suggestion spell gets disrupted, the other Suggestion spell "turns back on".

A Suggestion that conflicts with a Geas, too bad. He will do the Suggestion and he will take damage from the Geas that day. Assuming that the conflict does not deal with harming the target of the Geas caster. Geas is still a Charm spell.


This way, every spell that is cast works, just like if there were only one spell there. The only difference is that two exact same effects spell basically have one of them turned off. Same spell different effects results in both spells working.

 

[Arceliar]

A very good set of questions.

I think the simple ruling on this is:

All versions of all spells affect at all times. Only the exact same effect (or boosted same effect) does not repeat. In that case, only the most potent version works (if same potency, do not take best of 2 rolls). To be the same effect, it has to be the same spell (special abilities by monsters are not spells unless otherwise stated, so multiple similar or same effects are possible).

So, someone could have Geas on them from an ally, but a different Geas from an enemy would also still work. DItto Bestow Curse since disadvantage against two targets would result in two different effects. Enhance Ability for both Str and Dex results in both being boosted.

Two different Suggestions could result in a conflict, so some simple alternating save until one spell is gone might be needed. A spell that results in 100% compulsion like Suggestion needs a way for only one of them to work at a time if and only if they conflict (a Suggestion in a higher level slot would be more potent and hence win in a conflict scenario). The other Suggestion spells duration still exists and if the winning Suggestion spell gets disrupted, the other Suggestion spell "turns back on".

A Suggestion that conflicts with a Geas, too bad. He will do the Suggestion and he will take damage from the Geas that day. Assuming that the conflict does not deal with harming the target of the Geas caster. Geas is still a Charm spell.


This way, every spell that is cast works, just like if there were only one spell there. The only difference is that two exact same effects spell basically have one of them turned off. Same spell different effects results in both spells working.

What you've just described would be the case if multiple instances of the same spell applied the "union" of their effects, in the set sense of the word, which is not the same as the "most potent" rule the PHB gives, as far as I can tell. For the example with bless, and most other spells I can think of, it should have the same effect. Now that I think about it, I'm pretty sure the union is what I had as a mental model for how spells combine, until reading this thread and getting hung up on the Combining Magical Effects rule. I would not be surprised if this was the RAI. Maybe the RAI and RAW diverged when the authors/editors were trying to explain it succinctly. I'd be very happy to see an errata change that.

 

[KarinsDad]

What you've just described would be the case if multiple instances of the same spell applied the "union" of their effects, in the set sense of the word, which is not the same as the "most potent" rule the PHB gives, as far as I can tell. For the example with bless, and most other spells I can think of, it should have the same effect. Now that I think about it, I'm pretty sure the union is what I had as a mental model for how spells combine, until reading this thread and getting hung up on the Combining Magical Effects rule. I would not be surprised if this was the RAI. Maybe the RAI and RAW diverged when the authors/editors were trying to explain it succinctly. I'd be very happy to see an errata change that.

The PHB does indicate that the duration of the same spell overlaps.

So given your question, one either gets into the shenanigans that you mentioned, or one gets into segregating effects. Same effect, you only get it once. Different effect same spell, it get each effect.

I really cannot think of a way to avoid the shenanigans otherwise without coming up with a lot of corner case rules.

 

[Arial Black]

That still doesn't change that both are individual spells and in effect and are triggered at the same time, with just a single instance of the damage is applied.

That would be contrary to the rules.

Both spells cannot be triggered at the same time, because 'being triggered' is part of the 'effect' of the spell, and only one of the spells can have its effect.

I would seriously question a DM that ruled that a player is running around with an effect that can't be triggered

If the trigger is part of the effect (it is), and the effect cannot take place because the same effect from a previous casting is already in place, then the trigger, being part of that effect, is also prevented from occurring.

 

[Sorcerers Apprentice]

That would be contrary to the rules.

Both spells cannot be triggered at the same time, because 'being triggered' is part of the 'effect' of the spell, and only one of the spells can have its effect.



If the trigger is part of the effect (it is), and the effect cannot take place because the same effect from a previous casting is already in place, then the trigger, being part of that effect, is also prevented from occurring.

But isn't being subjected to the movement hindering energy also part of the effect? Shouldn't that also be prevented from occurring in the first place?

 

[Pathkeeper24601]

That would be contrary to the rules.

Both spells cannot be triggered at the same time, because 'being triggered' is part of the 'effect' of the spell, and only one of the spells can have its effect.



If the trigger is part of the effect (it is), and the effect cannot take place because the same effect from a previous casting is already in place, then the trigger, being part of that effect, is also prevented from occurring.

By that logic, the target would only have a single sheath of booming energy since the only one copy of the spell can be applied since they are the same effect. This effectively makes the discussion moot as there is no second sheath that can't be triggered.

Edit: Also, the rules don't say the effects don't occur, only that the results of a single instance are are applied. So nothing says that if both copies could be on a target (which by your logic they can't) that they can't be triggered at the same time, it just says that only the results of one of them is applied.

 

[Arial Black]

But isn't being subjected to the movement hindering energy also part of the effect? Shouldn't that also be prevented from occurring in the first place?

Okay, the sonic sheath is the effect.

The sonic sheath has several properties:-

* it triggers when the creature voluntarily moves from his square

* when triggered, it does sonic damage

* after dealing the damage, the spell ends

ALL of these are 'the effect' of the spell.

Since the effects of multiple copies of the same spell cannot combine, but the second spell still exists and its duration is counting down, then the original sonic sheath does what it does (trigger/damage/ends early) while the second sheath does not manifest at all while the first is still there, but the second spell still exists, still has its duration counting down and still successfully targeted the creature; the only thing the second spell is not doing is 'having its effect'. The second spell didn't evaporate! It will begin to have its normal effect the moment that the first spell is no longer preventing it from taking effect.

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.

Note that this whole subject is about the duration of two spells overlapping while being on the same target. It's saying that both spells have their usual effects if the spells are different, but if the spells are the same then, while their durations overlap, only one has its effect in play. This shows that it is not the case that the second spell fails and goes away; the second spell is still going strong, it's just that it doesn't do anything during that overlapping duration. It will start to do its thing as soon as the durations are no longer overlapping.

As soon as the first spell ends then its sonic sheath goes away. As soon as that sonic sheath (the 'spell effect') goes away then the second spell's effect will start to come into play, creating a new sonic sheath the instant the first one ended. It was only the existence of the first sonic sheath that prevented the second from appearing, but the second spell successfully hit the target and is still counting down its duration.

 

[Ovinomancer]

Okay, the sonic sheath is the effect.

The sonic sheath has several properties:-

* it triggers when the creature voluntarily moves from his square

* when triggered, it does sonic damage

* after dealing the damage, the spell ends

ALL of these are 'the effect' of the spell.

Since the effects of multiple copies of the same spell cannot combine, but the second spell still exists and its duration is counting down, then the original sonic sheath does what it does (trigger/damage/ends early) while the second sheath does not manifest at all while the first is still there, but the second spell still exists, still has its duration counting down and still successfully targeted the creature; the only thing the second spell is not doing is 'having its effect'. The second spell didn't evaporate! It will begin to have its normal effect the moment that the first spell is no longer preventing it from taking effect.



Note that this whole subject is about the duration of two spells overlapping while being on the same target. It's saying that both spells have their usual effects if the spells are different, but if the spells are the same then, while their durations overlap, only one has its effect in play. This shows that it is not the case that the second spell fails and goes away; the second spell is still going strong, it's just that it doesn't do anything during that overlapping duration. It will start to do its thing as soon as the durations are no longer overlapping.

As soon as the first spell ends then its sonic sheath goes away. As soon as that sonic sheath (the 'spell effect') goes away then the second spell's effect will start to come into play, creating a new sonic sheath the instant the first one ended. It was only the existence of the first sonic sheath that prevented the second from appearing, but the second spell successfully hit the target and is still counting down its duration.

Those passages don't state that the second effect is paused, though, just that it's not applied. It's still in effect. So, when it's trigger occurs, it triggers, but the effect is not applied to the target. There's no basis to assume that the second effect ignores everything until the first is discharged, only that whatever the second effect produces, it's not applied. If RAW or RAI was intended to have effects pause and resume, pretty sure it would clearly say that. Instead, it just says applied only the most potent effect to the target but otherwise the spell functions normally.

 

[Ovinomancer]

Okay, the sonic sheath is the effect.

The sonic sheath has several properties:-

* it triggers when the creature voluntarily moves from his square

* when triggered, it does sonic damage

* after dealing the damage, the spell ends

ALL of these are 'the effect' of the spell.

Since the effects of multiple copies of the same spell cannot combine, but the second spell still exists and its duration is counting down, then the original sonic sheath does what it does (trigger/damage/ends early) while the second sheath does not manifest at all while the first is still there, but the second spell still exists, still has its duration counting down and still successfully targeted the creature; the only thing the second spell is not doing is 'having its effect'. The second spell didn't evaporate! It will begin to have its normal effect the moment that the first spell is no longer preventing it from taking effect.



Note that this whole subject is about the duration of two spells overlapping while being on the same target. It's saying that both spells have their usual effects if the spells are different, but if the spells are the same then, while their durations overlap, only one has its effect in play. This shows that it is not the case that the second spell fails and goes away; the second spell is still going strong, it's just that it doesn't do anything during that overlapping duration. It will start to do its thing as soon as the durations are no longer overlapping.

As soon as the first spell ends then its sonic sheath goes away. As soon as that sonic sheath (the 'spell effect') goes away then the second spell's effect will start to come into play, creating a new sonic sheath the instant the first one ended. It was only the existence of the first sonic sheath that prevented the second from appearing, but the second spell successfully hit the target and is still counting down its duration.

Let me try this a second way. The rules say a thing works unless there's an exception. So, going into combining the same spell, we first must assume that both spells work as written, and then look for any exceptions. There is an exception in this case, and that is for two spells working on the same target, only the most potent effect is applied to the target. That's the exception, nothing else changes. So, when I review the spell effect, all of those things continue to work as written on the target with the only exception that the only effect applied is the most potent. Nothing there states that you pause the effect of a spell and only continue counting it's duration while a second spell of the same name is in effect. That exception is very different from only applying the most potent effect.

So, for booming blade (or any spell), both castings are checking the same triggers and resolving and ending as per their effects, but the target only ever has the most potent effect from both applied to them.

 

[Pathkeeper24601]

Okay, the sonic sheath is the effect.

The sonic sheath has several properties:-

* it triggers when the creature voluntarily moves from his square

* when triggered, it does sonic damage

* after dealing the damage, the spell ends

ALL of these are 'the effect' of the spell.

Since the effects of multiple copies of the same spell cannot combine, but the second spell still exists and its duration is counting down, then the original sonic sheath does what it does (trigger/damage/ends early) while the second sheath does not manifest at all while the first is still there, but the second spell still exists, still has its duration counting down and still successfully targeted the creature; the only thing the second spell is not doing is 'having its effect'. The second spell didn't evaporate! It will begin to have its normal effect the moment that the first spell is no longer preventing it from taking effect.



Note that this whole subject is about the duration of two spells overlapping while being on the same target. It's saying that both spells have their usual effects if the spells are different, but if the spells are the same then, while their durations overlap, only one has its effect in play. This shows that it is not the case that the second spell fails and goes away; the second spell is still going strong, it's just that it doesn't do anything during that overlapping duration. It will start to do its thing as soon as the durations are no longer overlapping.

As soon as the first spell ends then its sonic sheath goes away. As soon as that sonic sheath (the 'spell effect') goes away then the second spell's effect will start to come into play, creating a new sonic sheath the instant the first one ended. It was only the existence of the first sonic sheath that prevented the second from appearing, but the second spell successfully hit the target and is still counting down its duration.

Actually, the 'effect' of the spell is the melee attack that does additional damage and triggers the sonic sheath effect. You are starting your interpretation in the middle of the spell and ignoring the initial part.

So, you show that at that point both sheath effects must occur to meet the "while their durations overlap". Overlap does not exclude both spells from being in effect. As you show, they both must be in effect for there to be an overlap. I notice you don't highlight "the most potent effect ... from those castings applies". So both effects must be active and checked to determine the most potent. All effects respond to the same trigger on an individual basis, but only one result is applied. Nothing suggests sublimation of either spell, just application of a single result. One could be dispelled, and the other would still be there to provide damage if the target moves. In the same way, for Death Ward both copies would trigger when the target first goes to 0, but if one was dispelled, the target would still be under the effects of the other.