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Gnomish Workshop: Pierce de Resistance

This article was first broadcast in Episode One Hundred Ninety Nine on 9th February 2022.

Gnomish Workshop door opening
Ryu: What are you doing!?
Lennon: Gah! Um…this isn’t what it looks like
ROSTRO: Please state the nature of the mathematical inquiry
Lennon: No, no, you’re already working on mine.
ROSTRO: The assumption that my processing capabilities are limited to a single focus is erroneous.
Ryu: I thought you were on my side here!?
Lennon: Um…well I mean I came in here to ask Ostron a question and he…well he dropped off pretty quick actually, and the machine just started giving me some useful information…
Ryu: Ever heard of “fruit of the poisonous tree”?
Lennon: Look I was trying to figure out my spells, okay? I seem to be stuck with this Warlock thing so I may as well make the best of it. Are *you* going to help me choose what the most efficient spells are?
Ryu: You know I don’t handle the magical bits.
Lennon: Right, so I went to our resident wizard, and then the wizard went unconscious, and now I’ve got this.
ROSTRO: The information collation is largely complete, though note a thorough analysis only encompasses the information from four resources thus far.
Ryu, mockingly: Ohhh what happened to all those vaunted processing abilities?
ROSTRO: Given the request was placed one minute ago with expedited priority I initially limited my survey. A full analysis of all resources available for 5th edition will take slightly longer.
Lennon: How much longer?
ROSTRO: Thirty seconds
Ryu: I do not want to interact with this thing any longer than I absolutely have to. Let’s just go with this. Wait, what did you even ask about?
Lennon: Spell resistances.
ROSTRO: The analysis is concluded.


For most low level encounters and mundane creatures you don’t need to pay attention to damage types very much. About the only one that regularly comes up is if you’re fighting skeletons, in which case pass out the hammers and maces because you need that sweet bludgeoning damage.

However once you start climbing past CR 5 or adventuring in exotic locations there’s a greater chance that various enemies will have resistances or outright immunities to certain types of damage. If you have a character where they have methods of altering their damage type, or if they have access to spells at all, then it’s worth knowing how frequently various types of damage will be reduced or outright negated.

There are two complimentary mechanics involved. Damage reduction results in any source of damage being halved, rounding down in the case of damage values that are not even numbers.

Some clarifying notes on that mechanic. Sources of resistance are complimentary, therefore if a creature has multiple effects that convey resistance to a particular damage type, all that can apply, do. Resultantly if a creature that is naturally resistant to fire also dons a garment imbued with resistance to fire, they will reduce fire damage by half, and then reduce it by half again. A faster method would be to quarter the initial value but I have been informed some people resent that level of mathematical calculation.

Also, the sources of resistance are not mutually exclusive. If a creature is benefiting from resistance to damage from spells and resistance to fire, both resistances will again be applied in the case of something such as a firebolt spell being targeted at the creature.

The other thing about resistance is the whole halving issue. If you have a creature taking multiple hits that they’re resistant to, people who know a lot about math will argue that there is a big difference between totaling all the hits and dividing that in half as opposed to halving each individual hit. There is a difference, to be clear, but how much it matters is debatable. Basically, the more hits there are, the more when you cut the damage in half matters. As an example, say someone gets hit with Scorching Ray and they’re resistant to fire. Sorching Ray has three rays that do damage and for the sake of argument the creature being targeted didn’t bother to get out of the way of any of them. They each do 2d6 damage which averages to 7 and works perfectly for this example. Three sevens total 21 damage. Halved, that’s 10.5, which rounds down to 10 damage. However, if you halve each hit individually, that’s 7 divided in half to 3.5, which rounds down to 3 each. Three 3s totals to 9, so by dividing the numbers individually you saved yourself from taking…one whole point of damage.

Realistically that’s usually the best you can hope for unless you’re regularly defending yourself from multiple hits of magic missile at 6th level or higher, and Magic Missile is almost impossible to be resistant to anyway for reasons ROSTRO will make us tell you later. Short version, if you make a big deal about dividing the numbers beforehand, you’re going to maybe save yourself from losing 2 or 3 hit points over the course of the whole fight, and you will annoy anyone at the table that doesn’t like doing math, so good luck with that.

Immunity is at least simpler; the damage just doesn’t happen. It is important to note, however, that eliminating the damage doesn’t mean the attack, whatever it was, didn’t hit or wasn’t made. So if there are abilities or effects that trigger on keywords like “hits with an attack” or “casts a spell”, those still occur.

Now onto “what damage type should I choose for a spell.” And the answer is…Force. ROSTRO put up the numbers and even I can see there’s not even a contest here. Yes, the reason so many Warlocks stick with Eldritch Blast isn’t just for nostalgia or because it’s the cool thing to do (which it’s not, just to be clear). ROSTRO surveyed –

ROSTRO: Tested.
Lennon: Whatever.

There were 2006 monsters that ROSTRO went over and only ten had any kind of resistance or immunity to force damage. Not only that, two creatures actually had vulnerability to it. Vulnerability is the opposite of resistance; instead of halving the damage, you double it, and in 5e it’s very rare to find creatures with any kind of vulnerability at all; out of all the monsters only 88 had any kind of vulnerability at all, and 22 of them were the aforementioned skeletons. So the fact that force damage has some creatures vulnerable to it, and so few that resist it in any way, means it’s the clear choice for effectiveness.

Evidence suggests that enlisting the help of a quasi- or self-proclaimed deity is advantageous in producing magical damage as the next mathematically efficient category for damage output is radiant damage. While there are almost three times as many creatures that exhibited both resistances and immunities, that still only represents 1.5% of the total universe of creatures tested. Radiant damage also enjoys the second highest non-physical number of creatures vulnerable to it at 13.

Conversely, any attack which results in poison damage is the statistically worst available method of aggression. 510 creatures, effectively one quarter of the total collection, displayed a complete and unavoidable immunity to poison damage, with an additional 80 displaying some measure of resistance. Furthermore, only the bodytaker plant appears to possess any vulnerability to poison damage, which in no way offsets the severe handicap the damage type presents.

The second worst efficacy in elemental damage lies with cold damage, although the margins in this comparison are somewhat debatable. 101 creatures are totally immune to cold damage, with a further 237 being resistant to it, resulting in a total of 338 beings to whom cold damage is a substandard mode of attack. Compare to fire damage. The total number of creatures able to reduce fire damage is 322, less than with cold, however 136 of those are immune to fire, representing 6.8% of the total group, whereas only 5% of the group were immune to cold. Further complicating matters, 8 creatures presented with evidence of vulnerability to cold damage, while 31 seemed vulnerable to fire.

Ryu: Oh god the numbers…

What the whiny calculator is getting at is that fire and cold are probably on par with each other, but fire is more of a gamble; it hits more creatures harder, but there are also more creatures that will completely shrug it off, whereas with cold you’ve got more creatures that will be mildly annoyed by it and less that can just ignore it.

Speaking more generally, ROSTRO’s survey of the creatures –

ROSTRO: Testing.
Ryu: Okay…fine…

…testing of the creatures suggests the non-elemental damage types are much more likely to hit the way they’re supposed to, so Force, Radiant, and Psychic is the way to go. If for some reason you absolutely have to go elemental, aim for thunder damage; there are only 18 creatures with immunity to it, mostly the whispy cloud type creatures, and fifty eight are resistant, with five out of the 2000 being vulnerable to boot.

Now if you’re sitting there looking at your mundane weapon and swinging it around vainly hoping for some sort of spark to shoot out of the end, fear not! ROSTRO did not forget about you.

Ryu: “Fear not” isn’t the sentiment I would pick.
Lennon: The less you interrupt, the faster we get through this.

Now, there are only three different damage types for the mundane weapons; bludgeoning, piercing, and slashing, and ROSTRO has bad news for all the bards and rogues swinging those French pointers around. Out of the three, weapons doing piercing damage definitely lose out against the other two, with 43 creatures being resistant to it. Slashing only has 25 that are resistant, but it also has 9 that are totally immune (send a thank you to HR and all of its cousins for that one). Bludgeoning would seem to be the winner; it has 36 creatures resistant to it, but only 1 with immunity and a full 22 with vulnerability to the damage type where the others enjoy none.

Now a note about those numbers; ROSTRO only covered the creatures there with complete immunity or resistance to the mundane damage. There are another 285 with what it calls “fiendish immunity” or resistance. That’s the mechanic where the creature is immune or resistant to the damage, but only if it’s from a nonmagical weapon. “Fiendish” comes from the fact that most of the creatures with it are fiends of some kind, usually either devils, demons, or yugoloths. However it couldn’t find any examples where the three types weren’t grouped together, so it didn’t really matter for the comparisons.

Despite the accuracy of the data presented here, practical reality dictates that the conclusions drawn are not universally applicable. Depending on the probable scenarios any given adventuring group will encounter, the efficacy of certain spells will shift drastically. For example, a campaign largely focused around a raging conflict between orcs and giants is unlikely to produce a large number of creatures exhibiting the poison immunity warned against. Similarly the superiority of bludgeoning weapons will be far less apparent if the party never encounters extensive quantities of undead.

A prime example of this is the fact that dragons are a problematic species.

Ryu: Okay, you know what-
Lennon: Hey, no, put it…[to ROSTRO] you better finish up quick mate!

To clarify, in general certain resistances or immunities are frequently aspects of a particular species. Undead are almost universally resistant or immune to necrotic damage; fiends generally ignore cold, fire, and poison; and constructs exhibit immunity to poisons and psychic damage. Consequently, foreknowledge that ones primary adversaries belong to a particular taxonomic category often provides guidance regarding the most effective spell types to select.

Ryu: Dragons, however, are *wonderful and special creatures and they mess up the stupid machine’s math because it’s stupid!*
Lennon: Um…I know we usually paraphrase what’s on the screen but-
Ryu: Don’t push me!

Now, if the campaign or even the adventure involves a possible fight with a dragon, as opposed to a fight with a lich or something, that actually tells you very little about what to prepare unless you know the exact dragon in question. The reason, obviously, is that each dragon has a different elemental affinity, and the recent statting of the gem dragons has made that even more of a factor. You can’t even grab eldritch blast and be guaranteed it will work, since an amethyst dragon might wander into your line of fire and completely shut you down.

Ryu: Not that you should be trying to kill the dragons anyway. Ohhh that’s it! I am so done I just-
Lennon: Um, Ryu?
ROSTRO: Incorrect
Lennon: What?
KDM: Listen to me very carefully my good fellow because I’m only going to say this once. Get Ryu out of the workshop, now!
Lennon: But…um….you-
KDM: If she attacks ROSTRO, either she’s going to die, which will make me unhappy, or ROSTRO will explode, which will make me equally unhappy and will also level the Guild House and I think most of the surrounding area. But apart from that I will be unhappy. And you’ll be the only other one around.
Lennon: Right…um…fireman’s carry, or-
KDM: Just pick us up and get us out of here! ROSTRO darling you might want to make yourself scarce. Ryu seems a bit…oh drat
Ryu: Hey! Let go of me! [I will rip that thing apart with my bare hands, I don’t care what my Strength mod says!]
Continues threatening bodily harm to ROSTRO
Ostron: Whoa! Did I miss something?
Lennon: Explanations later, scrying pool now. Get the door!

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