# What happens when a creature is both vulnerable and resistant to the same damage type?

### Rules Questions

So let’s say, there is an Azer, which has weakness to cold. And they then cast Resistant Armor, Lesser on their self.

They pick Cold and Acid. So they now have Resistance 5 for cold and Acid.

How much damage would they take if they got hit with 8 Cold Damage.

I've always run it as half again (12) - 5 = 7 damage.

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No rule that I'm aware of, but as starfinder follows regular math unless specified otherwise, multiply then subtract.

That makes sense, thank you.

Garretmander wrote:
I've always run it as half again (12) - 5 = 7 damage.

That's how I've always run it as well, but reading this thread made me pause and think for a bit. And now I'm leaning the other way.

If I get hit for 20 points of electricity damage, and my Mk2 Electrostatic Field armor upgrade provides 10 points of resistance, that should lower the damage to 10 points. If I, personally, am vulnerable to electricity then the damage that hits me should be multiplied by 1.5, for a total of 15 points. Because my armor reduced the damage, and it wasn't particularly vulnerable to electricity. As opposed to a total of 20 if you multiply before the armor upgrade is counted.

Not saying I'm right here. And you could definitely ask questions like "but what if it was magical resistance granted directly to you?" (For consistency's sake I'd operate in the same order regardless of what the source of the resistance is.)

Belafon wrote:

If I get hit for 20 points of electricity damage, and my Mk2 Electrostatic Field armor upgrade provides 10 points of resistance, that should lower the damage to 10 points.

That's kind of begging the question. If a weapon does 20 points of electricity damage and you're vulnerable , are you "hit for" 20 points of damage or 30? Hit for doesn't have a defined order in the math here.

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The simple concept is that the damage would be affected by what one is wearing before it actually affects the one.

I don't think we should worry about the armor being hit first or whatever makes sense in a simulationist viewpoint, but from the gamist viewpoint.

PCs don't typically have vulnerabilities to damage types, NPCs do. Erring on the side of the PCs doing more damage and finishing fights quicker seems to me the better choice.

Lets the PC who planned ahead get more bang for their buck, even if the boss planned ahead as well.

Check to see what the PF2 order of operations is. I know there is one.

Xenocrat wrote:
Check to see what the PF2 order of operations is. I know there is one.

Isn't PF2 weakness 5, resistance 5? so they just cancel each other out? Sure, PF2 creatures/NPCs don't typically have both because they try and design for simple encounters and weaknesses are 'cleverly' disguised reasons for an encounter to have more hit points. But I'm pretty sure it isn't 'vulnerable fire' it's just 'weakness 10 fire' so they take 10 more damage from any fire damage, and resistance 10 fire just cancels out that vulnerability.

Don't know if this helps but I think in an old Pathfinder campaign there is a dragon who has prepared for the PC encounter. They have cast one of the resistance spells on themselves to reduce their elemental resistance, reducing the damage before their weakness kicks in. However that could also easily have just been my DM making it more challenging

I play the game to play a role playing game. If the rules are not specific, I choose what makes conceptual sense. And then I maintain consistency.

Garretmander wrote:
Xenocrat wrote:
Check to see what the PF2 order of operations is. I know there is one.
Isn't PF2 weakness 5, resistance 5? so they just cancel each other out? Sure, PF2 creatures/NPCs don't typically have both because they try and design for simple encounters and weaknesses are 'cleverly' disguised reasons for an encounter to have more hit points. But I'm pretty sure it isn't 'vulnerable fire' it's just 'weakness 10 fire' so they take 10 more damage from any fire damage, and resistance 10 fire just cancels out that vulnerability.

I don’t think you just sum them. If you take 4 points of fire damage with both resistance 5 and weakness 10 you can take either 9 (net them out, only apply 5 weakness), 0 (apply resistance first then weakness), or 9 (apply weakness then resistance.

I remember there is an order of operations, and I think it’s apply weakness first, but I’m not sure.

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Pathfinder Adventure Path, Companion, Starfinder Adventure Path, Starfinder Roleplaying Game, Starfinder Society Subscriber

I've always applied resistance before vulnerability. I consider it the final layer of defenses an attack needs to penetrate (which would also include miss chances, AC, and saving throws, in that order) to deal damage.

I don't think Starfinder or even Pathfinder 1E ever clarified the order of effects. (Full disclosure: Some PF1E devs did weigh in on vulnerability vs. hardness, when it came to robots, and decided that vulnerability was applied before hardness.)

But if you dig deep enough into the historical strata, the official D20 3.5 specified that resistance came before vulnerability. So, not an official Paizo ruling, but a precedent that's never been officially changed to my knowledge.

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The PF2 rule is on CRB 451.

"Apply immunities first, then weaknesses, and resistances third."

That plus the vulnerability/hardness thing makes me thing vulnerability should be applied first in Starfinder as a matter of consistency and implied developer trends in the company that make it probably this would be the outcome if the Starfinder devs did rule on it.

Pathfinder Adventure Path, Companion, Starfinder Adventure Path, Starfinder Roleplaying Game, Starfinder Society Subscriber

*nods*

BTW, by "the official D20 3.5" I meant to type "the official D20 3.5 FAQ," for posterity's sake.

Pathfinder Starfinder Roleplaying Game Subscriber
"Dr." Cupi wrote:
The simple concept is that the damage would be affected by what one is wearing before it actually affects the one.

Problem is, this means that two otherwise identical characters will have completely different efficacy, based purely on cosmetic differences. That would be a fairly terrible game design decision. If you have Resistance 10 to X, the effect should be exactly the same regardless of how you got it.

Metaphysician wrote:
"Dr." Cupi wrote:
The simple concept is that the damage would be affected by what one is wearing before it actually affects the one.
Problem is, this means that two otherwise identical characters will have completely different efficacy, based purely on cosmetic differences. That would be a fairly terrible game design decision. If you have Resistance 10 to X, the effect should be exactly the same regardless of how you got it.

For example?

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i'm late to the party but.
Generally I feel like resistances always proc first. Because it prevents incoming damage. vulnerabilities are triggered when you actually take damage. So, anything mitigating that damage cuts the amount coming in.

but I have no doubt that order of operation for me comes from Exalted and some video games and such. but its always what made sense to me. Since other effects (poisons, and I think biohacks) only work if enough gets through to trigger them. I always thought vulnerabilities were the same. It has to do actual damage to work.
So if something overwhelms the resistance it causes a stronger reaction~ kind of like soem allergies conditions.

I've always thought of 'taking damage' all being one step, one bit of math. No, 'this then that', just 'take the modified damage'.

So, starfinder following order of operations (multiply then add) is always what made sense to me.

Again, though, I would err on the side of helping out the players. Vulnerability then resistance tends to be better for them.

Pathfinder Starfinder Roleplaying Game Subscriber
"Dr." Cupi wrote:
Metaphysician wrote:
"Dr." Cupi wrote:
The simple concept is that the damage would be affected by what one is wearing before it actually affects the one.
Problem is, this means that two otherwise identical characters will have completely different efficacy, based purely on cosmetic differences. That would be a fairly terrible game design decision. If you have Resistance 10 to X, the effect should be exactly the same regardless of how you got it.
For example?

. . . Character X has Resistance 10 because of their armor. Character Y has Resistance 10 because of a cybernetic doohicky. Both are the same species with the same Vulnerability. If order matters, the same 15 point attack will do 10 to the one character, and 20 to the other. Despite having the same Resistance and the same Vulnerability. This is a bad situation, both because its tedious to track ( you need to know not just what a character has, but why they have it ), and poorly balanced ( because nothing in the game is priced around 'order of operation' mattering ).

Pathfinder Starfinder Roleplaying Game Subscriber
Garretmander wrote:

I've always thought of 'taking damage' all being one step, one bit of math. No, 'this then that', just 'take the modified damage'.

So, starfinder following order of operations (multiply then add) is always what made sense to me.

Again, though, I would err on the side of helping out the players. Vulnerability then resistance tends to be better for them.

*blink* How would "vulnerability then resistance" help the players? It would on average result in more damage, because the larger number is being multiplied. Or are you assuming that on average the enemies will have Vulnerability much more often than the players?

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That’s not an assumption, it’s clearly true.

Xenocrat wrote:
That’s not an assumption, it’s clearly true.

This exactly. There might be a race or two with vulnerability in the hundred+ playables, but I can't think of one off the top of my head.

But enemies sometimes do have vulnerabilities. Robots and fire type creatures immediately come to mind.

Metaphysician wrote:
"Dr." Cupi wrote:
Metaphysician wrote:
"Dr." Cupi wrote:
The simple concept is that the damage would be affected by what one is wearing before it actually affects the one.
Problem is, this means that two otherwise identical characters will have completely different efficacy, based purely on cosmetic differences. That would be a fairly terrible game design decision. If you have Resistance 10 to X, the effect should be exactly the same regardless of how you got it.
For example?
. . . Character X has Resistance 10 because of their armor. Character Y has Resistance 10 because of a cybernetic doohicky. Both are the same species with the same Vulnerability. If order matters, the same 15 point attack will do 10 to the one character, and 20 to the other. Despite having the same Resistance and the same Vulnerability. This is a bad situation, both because its tedious to track ( you need to know not just what a character has, but why they have it ), and poorly balanced ( because nothing in the game is priced around 'order of operation' mattering ).

Like what cybernetic doohickey?

"Dr." Cupi wrote:
Metaphysician wrote:
"Dr." Cupi wrote:
Metaphysician wrote:
"Dr." Cupi wrote:
The simple concept is that the damage would be affected by what one is wearing before it actually affects the one.
Problem is, this means that two otherwise identical characters will have completely different efficacy, based purely on cosmetic differences. That would be a fairly terrible game design decision. If you have Resistance 10 to X, the effect should be exactly the same regardless of how you got it.
For example?
. . . Character X has Resistance 10 because of their armor. Character Y has Resistance 10 because of a cybernetic doohicky. Both are the same species with the same Vulnerability. If order matters, the same 15 point attack will do 10 to the one character, and 20 to the other. Despite having the same Resistance and the same Vulnerability. This is a bad situation, both because its tedious to track ( you need to know not just what a character has, but why they have it ), and poorly balanced ( because nothing in the game is priced around 'order of operation' mattering ).
Like what cybernetic doohickey?

While it's a high level item (lvl 20), the seismic spine provides electrical and sonic resistance.

The seismic spine does not specify how it works, in concept. The item description is just full of crunch. I see no reason to conclude that the seismic spine doesn't just create a localized electromagnetic field that dampens both sound and drastic changes in charge. As it very well could be a localized field, damage would run through it before making it to the individual's body itself.

Any other examples?

I appreciate the discussion up to this point. It is solidly reinforcing my decision to default to apply resistance before weakness.

Just keep in mind that giving vulnerable enemies a resistance can nearly negate their weakness when designing NPCs (depending on CR) when estimating their challenge to the party.

Very true.