An immunity trick

[Anthrowhale]

The book of exalted deeds has two spells: Empyreal Ecstasy and Sublime Revelry which each make the target:

...take only half damage from all melee and ranged attacks...

Since these are two different spells each of which halve the damage, these effects accumulate. Hit points are abstract concepts, so the multiplication by addition rule applies. Hence, the multiplier is x(1-0.5-0.5)=x0. Hence, the damage from all melee and ranged attacks is reduced to 0.

Does anyone see a flaw in this?

If a Dragonborn Telthor takes Initiate of Mystra and Selective Spell then casts Selective[Self] Antimagic Field, Mystic Shield, Empyreal Ecstasy, and Sublime Revelry, what are the methods available to effect it?

[incorporeal] eliminates all mundane sources by default and Antimagic Field eliminate all magical sources by default. Note here that I'm assuming Selective[Self] AMF causes a AMF to not affect [self], although it separately affects spells that affect [self]. Initiate of Mystra is used to allow additional chosen spell effects on [self].

There are a few oddball effects left.

Transdimensional instantaneous conjuration(creation) spells which project into the AMF could damage an Incorporeal creature in an AMF. However, Empyreal Ecstasy + Sublime Revelry eliminates all damage. (Instantaneous Conjuration(creation) spells with an area of effect are suppressed by the AMF. The text in the RC makes this clear as does a careful reading of the PHB.)

Invoke Magic allows the casting of an L4- spell inside of an AMF. However, Mystic Shield makes you immune to the effects of all L6- spells.

A Serrenwood bow or arrows could damage an incorporeal creature inside of an AMF, but again Empyreal Ecstasy + Sublime Revelry shuts this down. This is true even if it's an elvencraft bow wielded as a staff.

Obviously enough castings of Disjunction could eventually break the AMF. Similarly another Initiate of Mystra could cast spells inside of an AMF. And Epic Spells have a chance of penetrating an AMF. What else is there?

[Troacctid]

The biggest problem I see is that division isn't multiplication. If it were, then passing your save against an empowered fireball would cause you to take the full non-empowered damage (150% - 50%) instead of half the empowered damage.

[Elves]

3 possible counterarguments

1) that while the rule amounts to net instances of +x, the application of the RAW involves reducing the value of the extra multiple by 1 which would arguably reduce the effect of the second spell to nil
2) that rather than multipliers (such as crit value stacking), these are two separate effects so each applies independently for net 75% reduction
3) that the rule for multipliers doesn't extend to division, like troacctid suggests.

Do we have any published examples of how divisions interact?

[Rebel7284]

I see two readings that make sense to me:

1. They don't stack at all. Both add a rule that if you were going to take damage, you take half instead. Since dividing damage by two satisfied both rules, you simply take half damage.
2. They both set up replacement effects that you can apply in any order you want, but either way, you end up preventing 75% of damage.

[Anthrowhale]

... division isn't multiplication.

Changes by a constant factor are specified in at least 3 ways throughout the rules: as division ("half" here), as multiplication ("x4" critical multiplier), and as a percentage (as in leap attack). The multiplication rule specifies only one of these, but applying it only when the word "multiply" is used seems excessively literal since there is no semantic difference between dividing by 2 and multiplying by 0.5 (or multiplying by 2 and dividing by 0.5). As an example, I interpret leap attack as giving an x3 power attack multiplier with a 2-handed weapon.

If it were, then passing your save against an empowered fireball would cause you to take the full non-empowered damage (150% - 50%) instead of half the empowered damage.

I disagree here. The process of specifying damage is distinct from the process of mitigating damage. In the game these are done by different people, for example. Specifying damage is done first, and then mitigation operates off the specified value. Stated another way, there is no "memory" about how damage is specified (other than explicit type information).

On the damage side, an enervated empowered fireball does 200% of normal damage. On the mitigation side, someone with fire shield[cold] who makes a save against any fireball (enervated, empowered, both, or vanilla) takes zero damage.

1) that while the rule amounts to net instances of +x, the application of the RAW involves reducing the value of the extra multiple by 1 which would arguably reduce the effect of the second spell to nil

I'm not quite following this. Each spell creates a multiplier of 0.5=1-0.5. The general formula for accumulation is that a multiplier of 1+x and a multiplier of 1+y create a multiplier of 1+x+y. Since x and y are both -0.5, you get a multiplication by 0.

2) that rather than multipliers (such as crit value stacking), these are two separate effects so each applies independently for net 75% reduction

If we accept that constant factor changes apply the abstract multiplier rule, then this seems to be ruled out.

Do we have any published examples of how divisions interact?

Well, Fire Shield, Radiant Shield, Investiture of the Orthon, and Piercing Cold provide examples. 3 of these 4 say 'zero' while one says 25%.

1. They don't stack at all. Both add a rule that if you were going to take damage, you take half instead. Since dividing damage by two satisfied both rules, you simply take half damage.

This is handled by the combining magical effects rules. Ruling that the second spell has no additional effect is contradicted by

Spells ... usually work as described, no matter how many other spells ... happen to be operating ... on the same recipient.

[Batcathat]

This is handled by the combining magical effects rules. Ruling that the second spell has no additional effect is contradicted by

I'm not sure that supports your argument. If the recipient takes half damage from attacks that fulfills the description of both effects. If anything, it could be argued that saying that the recipient takes no damage mean the spells doesn't work as described (since it specifically says the target "takes half damage", rather than something like "damage is reduced by 50 percent").

[Anthrowhale]

If the recipient takes half damage from attacks that fulfills the description of both effects.

Let's play with the idea.

1. If the recipient of an enervated empowered fireball takes 150% of normal fireball damage, that fulfills the description of both enervated and empowered.
2. If a leap attack charger wields a two-handed weapon and deals x2 power attack damage, that fulfills the description of both PA with two-handed weapons ("Special If you attack with a two-handed weapon... instead add twice the number subtracted from your attack rolls.") and leap attack ("...you deal +100% the normal bonus damage from your use of the Power Attack feat.").

Both of these interpretations seem rather controversial. How would you draw a line which avoids these interpretations while still collapsing EE+SR to half damage? I don't see a good one.

[Max Caysey]

The book of exalted deeds has two spells: Empyreal Ecstasy and Sublime Revelry which each make the target:

Since these are two different spells each of which halve the damage, these effects accumulate. Hit points are abstract concepts, so the multiplication by addition rule applies. Hence, the multiplier is x(1-0.5-0.5)=x0. Hence, the damage from all melee and ranged attacks is reduced to 0.

Does anyone see a flaw in this?

If a Dragonborn Telthor takes Initiate of Mystra and Selective Spell then casts Selective[Self] Antimagic Field, Mystic Shield, Empyreal Ecstasy, and Sublime Revelry, what are the methods available to effect it?

[incorporeal] eliminates all mundane sources by default and Antimagic Field eliminate all magical sources by default. Note here that I'm assuming Selective[Self] AMF causes a AMF to not affect [self], although it separately affects spells that affect [self]. Initiate of Mystra is used to allow additional chosen spell effects on [self].

There are a few oddball effects left.

Transdimensional instantaneous conjuration(creation) spells which project into the AMF could damage an Incorporeal creature in an AMF. However, Empyreal Ecstasy + Sublime Revelry eliminates all damage. (Instantaneous Conjuration(creation) spells with an area of effect are suppressed by the AMF. The text in the RC makes this clear as does a careful reading of the PHB.)

Invoke Magic allows the casting of an L4- spell inside of an AMF. However, Mystic Shield makes you immune to the effects of all L6- spells.

A Serrenwood bow or arrows could damage an incorporeal creature inside of an AMF, but again Empyreal Ecstasy + Sublime Revelry shuts this down. This is true even if it's an elvencraft bow wielded as a staff.

Obviously enough castings of Disjunction could eventually break the AMF. Similarly another Initiate of Mystra could cast spells inside of an AMF. And Epic Spells have a chance of penetrating an AMF. What else is there?

I would argue that selective spell does not affect AMF because amf affect magic and not creatures.. ergo you are being immune to effect that does not affect you! Secondly the rules talk about multiplication and not division, so that’s just out! Sorry, but I’d say everything in your argue meant is wrong!

[Darg]

Vulnerability to Energy

Some creatures have vulnerability to a certain kind of energy effect (typically either cold or fire). Such a creature takes half again as much (+50%) damage as normal from the effect, regardless of whether a saving throw is allowed, or if the save is a success or failure.

The question is, is this an exception or the rule?

Personally, I don't like having the multiplication rules apply to division. I rule it as an exception myself. (Saving throw for half +50%) * 50% * 50%

[Anthrowhale]

...amf affect magic and not creatures...

AMF causes incorporeal undead (PHB) or incorporeal creatures (RC) to "wink out". Selective [incoporeal creature] AMF implies they do not wink out. That's the only reason for selective spell here.

Secondly the rules talk about multiplication and not division...

This is addressed above.

[malloc]

Controversial reading maybe, but might 1/2 + 1/2 => 1/3 (increase by 1), similarly to how 2+2=>3?

My instinct is to say 75% damage taken, through standard math, but the above seems reasonable as well.
/e
For clarity, 1/2+1/2 => 33% damage taken, because the alternate (effects becoming less impactful) is silly.

[Anthrowhale]

The question is, is this an exception or the rule?

I don't understand well enough. I've always thought of vulnerability as implying 150% damage if you fail the save and 75% damage if you don't based on the "find damage total, then find damage mitigation, then record total damage" algorithm. Reading carefully though, it seems like you could parse it so that you get 100% damage on a save. Which is your preferred parse?

Controversial reading maybe, but might 1/2 + 1/2 => 1/3 (increase by 1), similarly to how 2+2=>3?

This seems like a reasonable house rule.

It seems like several people draw a distinction between division and multiplication which I find very unintuitive. My view is drawn from 2*x = x/0.5 and 0.5*x = x/2 so multiplication 'is' division and division 'is' multiplication. I realize we use different words and symbols, but the semantics are shared making them synonymous for me.

[Kitsuneymg]

AMF causes incorporeal undead (PHB) or incorporeal creatures (RC) to "wink out". Selective [incoporeal creature] AMF implies they do not wink out. That's the only reason for selective spell here.

This is addressed above.

I’m going to argue you’re wrong. I mean, you’re right mathematically. But you’re wrong game wise.

WotC treats increases and decreases differently already and explicitly in parts of the game. Just look at stacking rules. Bonuses of the same type don’t stack, but penalties do, despite a penalty being mathematically the same as a negative bonus. Also, calling a -1 morale penalty a negative bonus would make it go away is you had a +1 morale bonus since only the highest bonus stacks. This is obviously not the intention nor is it the raw afaict.

Since there is explicit rules for -1 being treated differently than +(-1), I would say there is precedence for multiply by 1/2 and divide by 2 being different. And since they use division explicitly, I contend they are not meant to touch the multiplication rules.

[Elves]

I'm not quite following this. Each spell creates a multiplier of 0.5=1-0.5. The general formula for accumulation is that a multiplier of 1+x and a multiplier of 1+y create a multiplier of 1+x+y. Since x and y are both -0.5, you get a multiplication by 0.

they word this process as
"When two or more multipliers apply to any abstract value, combine them into a single multiple, with each extra multiple adding 1 less than its value to the first multiple. Thus, a double (×2) and a double (×2) applied to the same number results in a triple (×3, because 2 + 1 = 3)."
In this case, what is "1 less than the value" of .5?

[gijoemike]

I am going to be the odd man out with my interpretation on this. But I don't think these spells should combine with the multipliers in any way. I read this as a spell effect that takes place long after the damage multiplier is calculated and resolved. The spell effect is take 1/2 of the total damage you would be dealt from source X. It wouldn't matter if you had 2, 3, or 4 similar effects the end result would be to take only half the total calculated damage. No multiplication game happens. Let me explain further.


In Mathematics Multiplication and Division are resolved in reading order at the same time. But you can move items around and still get the same answer because division is just multiplying fractions afterall.

2 * 3 / 2 = 6/2 = 3
2 / 2 * 3 = 1 * 3 = 3
3 / 2 * 2 = 1.5 * 2 = 3

Lookie, they are all the same result!

But in D&D math adding in a 1/2 anywhere except the extreme end doesn't work.
Also it breaks the additive property of the D&D math.

Spirited Charge with crit with a x2 weapon can be calculated as such.

feat(x2) + crit(x1) = x3 total damage
crit(x1) + feat(x2) = x3 total damage

So D*D turns multiplication into addition but it retains the same result if things are moved around due to the commutative property of mathematics.


Arguing that the Spells should be included at this phase results in

feat(x2) + crit(x1) - spell(.5) = 2.5? <<<<< This is new. Clearly not intended. We cannot roll this.

arguing the spell effect goes at the very end and is not additive. Besides being against any and all rules pertaining to the subject and rules of mathematics. What is about to be calculated hurts a math teachers soul...

feat(x2) + crit(x1) * 1/2 = 1.5x << how does one roll this?
feat(x2) * spell(1/2) + crit(x1) = 2x << that doesn't match any intended affect.
crit(x1) * spell(1/2) + feat(2x) = 2.5 << Huh? Spell barely makes a dent now.


The only way for it to work is thus
Feat(x2) + crit(x1) = x3 || crit(x1)+Feat(x2) =x3
Roll the 3x damage.
Calculate total which we will mark as variable T.
Damage taken = T/2. <<< This is in a completely different phase after the roll and total calculation.

No matter how many spell effects are cast on the target the end result is T/2. There isn't any ((T/2)/2)/2/2/2... The spell effect takes T and does math to it. The different spells don't interact, they don't stack effects with each other. You get 2 different effects of T/2. At best it is a dispel safety net.

[Anthrowhale]

Bonuses of the same type don’t stack, but penalties do

A difficulty with this argument is that penalties don't have types so they are symmetric to untyped bonuses which stack.

In this case, what is "1 less than the value" of .5?

-0.5? That was my interpretation.

Damage taken = T/2. <<< This is in a completely different phase after the roll and total calculation.

I agree with damage mitigation being a different process.

You get 2 different effects of T/2. At best it is a dispel safety net.

I disagree here. Reading through combining magical effects, the default is that:

Spells ... usually work as described, no matter how many other spells ... happen to be operating... on the same recipient.

So, the default is that each spell works without interference from the other. There are many caveats that come next, and they must all be checked. A few notable ones:

1. This is not a 'penalty on damage roll' since it's not subtracting a fixed constant.
2. There is no type associated with this effect so type stacking rules do not come into play.
3. EE and SR are not identical spells so this is not an example of "same effect more than once in different strengths".

[Elves]

-0.5? That was my interpretation.

So you're arguing that two .5 multipliers become .5 + (.5 - 1) = 0?

[Anthrowhale]

So you're arguing that two .5 multipliers become .5 + (.5 - 1) = 0?

Yep, this seems like the consistent view.

It's specified as what happens in {Fire Shield, Radiant Shield, Investiture of the Orthon), but not Piercing Cold (where .5 and .5 means .25).

Searching for another, this is also what happens with miss chances, except that they are explicitly capped at 50% in the RC.

[Darg]

Piercing Cold uses the language "half damage," not x times or half again as much, or +50%.

Fire shield and such use the language "half damage." Based on piercing cold, half damage means exactly that: half damage. Those spells say it negates damage on a save, so no matter the multiplier it would still do 0.

[Anthrowhale]

Piercing Cold uses the language "half damage," not x times or half again as much, or +50%.

Yep.

Fire shield and such use the language "half damage." Based on piercing cold, half damage means exactly that: half damage. Those spells say it negates damage on a save, so no matter the multiplier it would still do 0.

The set of instantiations of constant < 1 multipliers seems to be:

...take only half damage ...take no damage on a successful save

...takes half damage... takes no damage on a successful save...

...deal half damage... (or one-quarter on a successful saving throw)...

... only the highest miss chance applies...

So, 3 defensive instances have x.5 and x.5 implying x0 (or, /2 and /2 implying /\infty if you want to think that way). 1 defensive instance (miss chance) has x.5 and x.5 implying x0. 1 offensive instance has x.5 and x.5 implying x.25. Are there any other instances?

[Elves]

Yep, this seems like the consistent view.

It's specified as what happens in {Fire Shield, Radiant Shield, Investiture of the Orthon), but not Piercing Cold (where .5 and .5 means .25).

Searching for another, this is also what happens with miss chances, except that they are explicitly capped at 50% in the RC.

Yeah, that looks technically legit then. Although I expect the intent was for them to apply separately, successively, rather than triggering the multiplier rules. Nor do I expect WOTC was especially rigorous about using "50%" vs "half damage", @Darg.

[The_Jette]

As the DM, I would rule that if you had the spell effect of taking half damage from all attacks, and that it came from two different sources, that you took half damage. Personally, I see it as gaining the same bonus from two different spells. And, it's similar to having DR from two different types (e.g. 5/magic dr at the same time as 3/cold iron dr; if the attack isn't magic, you subtract 5 from it, but if it is magic and isn't cold iron you subtract 3). So, if one gets dispelled, you still have the other. That's how I'd rule it.

[Darg]

As the DM, I would rule that if you had the spell effect of taking half damage from all attacks, and that it came from two different sources, that you took half damage. Personally, I see it as gaining the same bonus from two different spells. And, it's similar to having DR from two different types (e.g. 5/magic dr at the same time as 3/cold iron dr; if the attack isn't magic, you subtract 5 from it, but if it is magic and isn't cold iron you subtract 3). So, if one gets dispelled, you still have the other. That's how I'd rule it.

Damage reduction isn't a bonus or penalty. As such the same type modifier rule doesn't apply. It's even shaky that damage reduction against the same type doesn't stack, but what can you do against something so vague and has such mass assumption behind it.

Either way, if you can only halve damage once then what about damage multipliers? Shouldn't they follow the the same rule for fairness and balance?

[The_Jette]

Damage reduction isn't a bonus or penalty. As such the same type modifier rule doesn't apply. It's even shaky that damage reduction against the same type doesn't stack, but what can you do against something so vague and has such mass assumption behind it.

Either way, if you can only halve damage once then what about damage multipliers? Shouldn't they follow the the same rule for fairness and balance?

No, they shouldn't. Because they're not the same thing. Consider this: you have to roll to confirm if a critical hit is a critical hit or just a regular hit. But, you don't have to roll to confirm if a crit fumble is a regular miss or a critical miss. Why aren't they the same for fairness and balance? Because they're entirely different situations that should be handled differently. If someone has two spells that both grant half damage from attacks, that's what they're getting. They're getting half damage from attacks.

[JNAProductions]

No, they shouldn't. Because they're not the same thing. Consider this: you have to roll to confirm if a critical hit is a critical hit or just a regular hit. But, you don't have to roll to confirm if a crit fumble is a regular miss or a critical miss. Why aren't they the same for fairness and balance? Because they're entirely different situations that should be handled differently. If someone has two spells that both grant half damage from attacks, that's what they're getting. They're getting half damage from attacks.

Critical misses aren’t RAW, though.

You miss on a 1, but that’s it. Nothing worse happens.

[The_Jette]

Critical misses aren’t RAW, though.

You miss on a 1, but that’s it. Nothing worse happens.

I agree. Which is not the same thing that happens on a critical hit. Which was my point. I was just saying that just because two things are opposites of each other doesn't mean that you have to do anything to balance them out, since they're not necessarily the same thing anyways.

[Darg]

No, they shouldn't. Because they're not the same thing. Consider this: you have to roll to confirm if a critical hit is a critical hit or just a regular hit. But, you don't have to roll to confirm if a crit fumble is a regular miss or a critical miss. Why aren't they the same for fairness and balance? Because they're entirely different situations that should be handled differently. If someone has two spells that both grant half damage from attacks, that's what they're getting. They're getting half damage from attacks.

Reflex save for half damage. Fire shield for half damage. You save and take half. Fail and take half. Is this what you are saying?

[The_Jette]

Reflex save for half damage. Fire shield for half damage. You save and take half. Fail and take half. Is this what you are saying?

Nope. Didn't say that at all. What I said was that if you have two spells that do (literally) the same thing, you get the effect. If you have fire shield (half fire damage), and another spell that also gives you half fire damage, you would take half fire damage on a failed reflex save. That's what I'm saying.

[Anthrowhale]

What I said was that if you have two spells that do (literally) the same thing, you get the effect.

1. The effects of Empyreal Ecstasy and Sublime Revelry are not identical. They just have some identical elements.
2. The spell stacking rules say that by default spells stack, then lists exceptions. None of the exceptions apply here.
3. Starmantle also generates half damage, but of a different sort (weapons only and requires a reflex save to activate). If you want to avoid accumulations resulting in immunities, it would need to be based on something other than identical elements to effects.

Overall, I think it's very reasonable to houserule in a way which prevents immunities, but some care is required.

[The_Jette]

1. The effects of Empyreal Ecstasy and Sublime Revelry are not identical. They just have some identical elements.
2. The spell stacking rules say that by default spells stack, then lists exceptions. None of the exceptions apply here.
3. Starmantle also generates half damage, but of a different sort (weapons only and requires a reflex save to activate). If you want to avoid accumulations resulting in immunities, it would need to be based on something other than identical elements to effects.

Overall, I think it's very reasonable to houserule in a way which prevents immunities, but some care is required.

I understand what you're saying but disagree with your conclusion. The spells are not identical, so the non-identical parts would be in place. But, the identical parts, specifically that of causing the target to take half damage from attacks, would not stack. It's not a house rule but an interpretation of rules as written. You and I can look at the same piece of written information and understand it to apply in entirely different fashions. I was simply trying to add to the conversation with my interpretation of how the rules were written.