Vulnerabilities, you say?

Some of them can be killed with physical trauma but others are too tough and will only die to fire or drowning or something.

...Too tough for physical trauma to take?  How the heck is that happening on a biological basis, you don't normally get that sort of thing outside of deep-sea geothermal magnet harpoon snails!

Well, it might just be that they haven't invented machine guns.

Sure, she'll get right on that in between the thousand other inventions she can't secure workshop space to start making.

Have they invented guns yet?

Nope.

Well, there's a start.

Sulfur, saltpeter, charcoal.  She has a vague impression of a 5:3:1 ratio in some factor to be the best, but she can probably just make a best guess at the products and stoichiometry out the rest...

S, KNO3, C (plus various, but mostly just...C.) -> CO2, N2, SO2?, K???/KN??? - do the lookup...

Well, she'll need paper first, this is a bit much to do in her head.

...Sure would help if she remembered how electron shells work, but it is the periodic table...

s shells contain 2 electrons, p shells contain 6 electrons...

s p -> 2s 2p -> 3s 3p -> 4s 3d 4p ...d shells contain 10 electrons but weirdly...Okay she doesn't need to worry about d shells, K just barely scrapes 4s.

K -o, O ----oo, C --oooo, N ---ooo, S ----oo...

K2S?

S, 2 KNO3, 3C -> K2S, N2, 3CO2?

Potassium sulfate?  Potassium sulfide?  ...those are different chemicals, hmm.  ...SO4 is a thing, H2SO4 is a chemical she remembers existing from a truly horrible black-humor sort of poem...

(That might change the math, ugh.)

S, 2KNO3, C -> K2SO4, N2, CO2?

Alright, she has any idea.  The rest is just shutting up and multiplying.

Probably.  Maybe.

6.02*10^28, don't fail her now.

...wait, she doesn't need mass-in-grams, ratios are dimensionless.

C=12.0

N=14.0

O=16.0

S=32.1

K=39.1

32.1 : 2(39.1+14.0+3(16.0)) : 12.0

32.1 : 2(39.1+14.0+48.0) : 12.0

32.1 : 2(101.1)(39.1+62.0) : 12.0

32.1 : 202.21, adjust sigfigs after math, dangit... : 12.0

32 : 202 : 12

/ 4

8 : 50.5 : 3

...Well, it's close to 3 : 5 : 1, like she was expecting originally, if you squint really hard.  More like 3 : 16 : 1.

Mythbusters did determine that ratio empirically, anyway.

(And it didn't create a diamond-shooting cannon in conjunction with bamboo, though it probably would've worked with enough duct tape.)

...Maybe she should check the other one, too, just in case.

32.1 : 202(.1) : 36.0

32 : 202 : 36

8 : 50.5 : 9

2 : 12.5 : 2.25.

Well, she'll test both.

"Hah!"

"...ssh, me."

Alright, now to invent the breech-loading rifle...

And maybe see if Wheat's around.

Wheat is in in his office again this time, doing some kind of paperwork!

"Heya.  I come bearing gifts.  Namely, the correct ratio of elemental sulfur, saltpeter, and charcoal - elemental carbon, really - to make gunpowder with, for when you need to make things explode.  And also probably gun design tips, but that's a matter for militarily-minded folks, not ourselves."

"All right, sounds exciting," says Wheat. "This is for, what exactly, I don't often find I want things to explode..."

"I can think of plenty of things that need exploding, right over on the other side of the Barricade!  ...Probably not right over there, but, y'know, demons are very explode-able!"

"They can't usually get over the wall, but yeah, that's true. Do you like, throw this stuff at them, or -"

"You can wrap it in a metal casing and shove it down their throats, but it's more often used to propel metal or rock at things, very fast, from a safe distance.  That's why I mentioned guns; they're weapons suitable for that purpose.  You stick the 'gun'-powder in a metal tube with a closely-fitted projectile, you ignite the gunpowder, the gunpowder goes boom and launches the projectile out, faster than the speed of sound."

"Oh, interesting. That does sound like it might puncture some demons' armor."

"Sure would, yep!  Wish I knew the formula for smokeless powder, honestly.  Black powder, the iconic example of gun powder, very definitively creates smoke.

"On the other hand, once we have electrical generators and can reliably troport electrical resistance...I bet we could make railguns.

"...or coilguns, or other sorts of 'shoot a projectile really fast, but this time with magnets'.

"Because the main problem was - is - well, partially power draw - but more keeping the electrical resistance from melting the gun, if I recall correctly, and if you transfer that out of your wiring, boom, you have a room-temperature superconductor.  And those are just bullshit."

"I've lost you."

"Yeah, it's not stuff that I really understand the theory of myself; I just know that you can create nonzero net force, and therefore motion and work, from electrical current slash electrically-induced magnetic fields.  Electricity and magnetism are actually the same fundamental particle interaction, just...perpendicularly.  ...You do have lodestones, right?  ...oh, hell, would you?  I don't..."

Are north, south, east, and west meaningfully directions?

The language does not appear to have words for them!

"...Well, anyway, if you've ever found a rock that iron sticks to, that's magnetism at work!"

"Yeah, magnets are useful, I use them for stirring sometimes."

"Magnetism is quite literally perpendicular to electricity, I should note.  You can generate electricity by moving a magnet through coiled wire."

"- that's so... random," says Wheat.

"Not if you understand electromagnetism, apparently!  Ironically, despite the simplicity of modeling it, the least-understood fundamental force of my homeworld was gravity.  Which is...actually plausibly a lot weirder, around here, because infinite planes do not make pleasant equation-fodder...Also, fun fact, light is also part of electromagnetism.  In addition to a whole bunch of other weird shit that goes on with light, because sometimes whether it's a particle or a wave depends on whether you're looking.  Not that we'll have the infrastructure to repeat the double-slit experiment anytime so-ooooh, but chemical photography might work... but...yeah.  Light's weird as fuck.  ...I should probably sit down with a physicist, if you have any, sometime soon.  I don't want to forget what I know, and I have less study material available."