Caves don't occur deeper than 3,000 meters in nature due to the pressure exerted by the earth at such depths

He was in the points of light setting? Probably one of the cooler gods I have seen considering how he just thrashes madly around underground with fucked up legs and his blood gave life to the monsters in the underdark not to mention "The King that Crawls" just sounds fucking cool.

In my experience, trying to explain things in 'realistic' terms will just fuel player nitpicking.

Saying 'It's magic', or sticking to a metaphysical explanation works best.

>How would you justify a under dark-esque series of caves and tunnels that goes deeper than this

You don't. You say "There is a cave system that... just keeps going past the limit. We have no idea how, or why, or what's past the 3,000 mark."

This is worth fleshing out, imagine a world where magic as a force naturally warps the world to be fantastic and grand, perhaps over exposure to magic might make a person believe they are the hero in a story?

The Earth surrounding the cave has enough Cavorite ore around it to counteract the high pressure, making it possible for the cave to be that deep.

Yeah magic.

So it super deep mining possible? Will we have to start to do more dangerous, extreme, insane operations into the bowels of the earth to rip it clean of more and more and more resources until we're finally wiped out?

What does the magic do that allows caves to form more than 3,000 meters deep?

I think we can build supports when mining that can support more wight than caves usually can

Disregard pressure, for starters

Everything it needs to

A cave filled with an approximately incompressible medium is already sufficient. Just pump your mine full of liquid and work in that. Similar things already allow us to extract otherwise unreachable oil sources.

Why do you assume gravity, pressure and so on work in a way that's analogous to reality? You're in a setting defined by elemental alchemy and mysticism, with divine creation and planes that completely defy rational analysis. Just because it seems to have similar results on the surface is no reason to assume it's the same all the way down. The very fact the underdark and similar exists can be taken as proof of this.

One of my favourite ways to flesh out the metaphysics of the setting is to simply say that physics exists exactly as it does in real life, but magic is another, new, and extremely important fundamental force that has subtly influenced absolutely everything, from quantum interactions to macro-astrological formations since the beginning of time, with higher concentrations creating stronger lapses in standard physics until it's dispersed.

Not to be an obstinate ass but why? fleshing out the explanation could give a lot of detail to the world

There is a portal to the Elemental Plane of Caves, where caves over different physical laws at the 3000m mark.

Alternatively a portal back to 100m so it really just FEELS like the caves go deeper and deeper

To be clear this isn't meant as a criticism of DnD, I just thought it would be interesting to see what different explanations people could come up with

Nobody knows. Maybe if you stop bothering the GM with questions and actually get on with adventuring, you'll have a better chance of finding out.

I wish I was a player, I am my groups perma-GM

Gigantic crystals form support columns for the caverns.

Adamatine veins provide unseen support in the earth for the caverns.

The sides of the caverns have been treated magically by the secretions of the dholes and bholes that made them.

In other words, ANYTHING.

Why?

Autism demands rigid rules and definitions of everything. Mystery and disorder are anathema, to be hated and screamed and screamed and SCREAMED at until they get their way and the hard numbers make them feel safe again.

No one here is screaming

Not every setting has to be fully detailed and explained but what's wrong with having a more detailed a fleshed out setting?

No! Am progress!

It would be interesting if an empire or something executed people by throwing them out the bottom of the world

I'd post that "it depends on the setting" pic but someone already posted it

I'm guessing OP is fishing for explanations for a home brew setting

3000 meters is deep enough.

3,000 meters of cave isn't enough for you?

No, for a reason that's hard to explain it's not

I remove the page in the geology book that says:
>Caves don't occur deeper than 3,000 meters in nature due to the pressure exerted by the earth at such depths.

Why are you so upset? it's not like OP is shitting on people for having less realistic settings

The Underdark reaches depths of 10 miles, which is 16,093 meters deep. Over 5 times as deep as the deepest naturally occuring caves in the real world. OP is asking how such a thing or its equivalent could be explained.

>so fucking deep

I know the word autism gets thrown around a lot on the Internet, but this time I genuinely think it's real.

First day on Veeky Forums? Autistically delving into the logic of fantasy or other stuff is a staple of the board.

Under rated post

Nah, this time is fine. It would be autism if he was screaming something about how D&D is unrealistic because the underdark is deeper than 3000 meters then it would be autism. Just coming up with explanations for fantastical elements isn't autistic, it's just worldbuilding.

Honestly, the "It's fantasy, I don't have to explain anything" crowd is just as bad.

It's not very interesting desu. It's an answer to a question no one ever asked and no one really needs to know to enjoy the setting. Hopefully.

Honestly I can understand why some people get upset at trying to explain fantastical elements as it's been done poorly a lot, that being said OP doesn't seem autistic and deserves better than "it's magic I don't got to explain shit"

>The Underdark reaches depths of 10 miles, which is 16,093 meters deep.
That's insane, but the writers obviously have no sense of scale.

I think the idea is that an explanation would lead to more interesting world building, for example if there's an ore that provides the necessary support to prevent the caves from collapsing you suddenly have a rare ore with interesting properties native to the deeper caves

Things like these add flavor to the setting, and it helps with immersion.

No explaining unimportant details is fine, you obviously can't explain everything, but explaining unimportant details in terms of in-setting rules usually helps the players understand the rules better and maybe they can come to utilize these factoids in their plans.

Let me try to present an example:

A player asks the GM how are these caves deep underground possible. The GM answers "It's fantasy, I don't have to explain" and that's the end of the discussion, not very interesting. On the other hand, the GM might instead answer "Mana runs through crystal columns and fills in the gaps, providing the columns with great strength" which then becomes information that the player can use in a plan, for example to disrupt the mana in some columns to collapse the ceiling in a section of the caves.

In the end, worldbuilding details like that add a lot to the immersion and make the world feel more like a world and less like a game.

I'm of the opinion that if the players ask a question about the world, the GM should never answer with "That's just how it is" or "Doesn't matter, it's fantasy" because the only thing this achieves is remind the players that they're in a game and is in no way interesting. The better option, if the GM doesn't have an answer ready is to bullshit his way through an explanation (and write it down for further reference).

a plane thats inverted. Instead of a ball where people live on the outside, its a sphere and people live on the inside. The sphere is so massive that it seems flat and clouds obscure the horizon. The sun is actually a duo of magical entities that are bright and dim respectively and emit a sort of reverse gravity that pushes things away so people dont "fall" towards the center of the sphere

It's the membranous plane that separates the Prime Material and the Elemental Plane of Earth.

Past a certain depth, the Elemental Plane of Earth exerts increasing amounts of pressure on the Prime Material. The result is a sub-plane of the Prime Material that is closely associated with the Elemental Plane of Earth, acting as a barrier that prevents it from directly leaking into the Prime Material.

To extrapolate on this, the Prime Material has three other membranous sub-planes associated with each of the other Elemental Planes, where physics doesn't function as it truly should.

The God of Caves decided that law was stupid and unfairly hampered his domain and repealed it. Next.

But the God of Science decided to reintegrate it.

Fuck your god

I like to come up with something cool for me, but remind the players that while there might be wizards researching cave formation, their characters wouldn't know what happened or why.

At the absolute worst, the GM can give a "unfortunately nobody knows how X works, the secret seems to have been lost to time" or something similar, giving an in-setting answer of vagueness, but that's just as a last resort. Giving actual answers is always better.

I mean if the player's character has an academic background they should know something is up, high-school level physics would let you know that a cave can support only so much weight

Only if high school physics applies to the fantasy setting. Which it doesn't, necessarily.

But this would only be true for a planet with the same circumference, mass and density as Earth. Why would a fantasy world have any of these in common?

>Giving actual answers is always better
Yeah, the caveat being that even if there is an answer the PCs might not know it.

What I do in those cases is have an answer ready anyway, but I only tell the players what they character would know or deduce, and then if they decide to inquire further, they may come across a useful answer.

Also, if I know the answer myself, even if I don't tell the players, I can use it for the game in case the players do something that would have unintended side effects,like a cave collapse because they accidentally drained the mana from those crystals, for example.

Beyond that, why would a fantasy world care about its circumference, mass and diameter, necessarily?

That doesn't make sense, by that logic caves would be even less deep since the plane of earth constantly tries to close any non solid gap.

Because things have the same weight in the setting which suggests that the gravity of the planet is the same

There is nothing saying that a fantasy pound is equal to a real world pound

Why? People observed things falling for centuries before gravity became understood and accepted. The exact same surface level details could be based on an entirely different set of principles with very different implications.

The general rule for fantasy is that if it's not explicitly mentioned as being different, it's the same as our world.

Thus, even if the functional details of gravity are different, it would still be safe to assume that it's 9.81 m/s^2 and that a 50 meter fall would kill an regular human. Similarly, Newton's laws of motion would apply the same in most cases, aside from explicitly mentioned exceptions.

Just saying "It's fantasy, so no real world rules apply" is exceedingly unhelpful and hinders players.

That aside, even if our high school physics don't apply at all, a fantasy world would have it's own version of high school physics in which an educated character would know.

naturally occurring portals that artificially expand the underground into other cave systems and even other planes.

If you don't say that a fantasy pound is different to a real world pound, it is assumed that a fantasy pound is equal to a real world pound.

I've always thought it more that, unless otherwise stated, it is similar enough to be analogous, not absolutely the same.

Are they though? Consider strength weight limits vs what's actually achievable.

If you're going to have a legitimate explanation for why caves can go so deep you might as well have a legitimate explanation for how strength 20 and beyond works.

This is a prime example of a slippery slope.

That's why dwarf live in mountains bucko.
They don't dig 3000m down. But thousands of meters mostly horizontally.

The weight of a fantasy pound is usually treated as roughly equivalent to real pound, for example the amount of weight that the average person can handle is roughly the same

Have you tried not playing DnD?

Which of course then gets you looking at non magical monstrous creatures with entirely impossible physical makeups, especially amongst the flying and swimming creatures.

Rule of cool

OP didn't state that this was set in DnD and besides strength rules are a part of the systems rules not necessarily canon to the setting

Post another setting then. It'll either be A) Realistic enough that a cave that deep shouldn't be in the setting or B) fictional enough that an explanation doesn't need to be realistic.

That's exactly what I said.

It's the same in the sense that if something would work in the real world, it would work the same in the fantasy world unless explicitly stated. The underlying reasons might be entirely different but that hardly matters.

In effect: The "What" is the same, but the "why" might be different.

However, I'd go as far as to say that if there are no details implying that the "why" is different, then the "why" is also the same.

Looking at gravity: If you state that the world is flat and nothing else, I would expect gravity to still accelerate me a 1g, but why gravity works like that on a flat world is different. On the other hand, if you don't state anything about the world, I will assume that the world is a sphere of about the same mass as Earth and gravity works the same way.

Basically my point is: Anything not explicitly stated as different is the same. Also, as a player, if you spring those differences on me in the middle of a plan I made because you didn't introduce the differences beforehand and I assumed everything was the same, and those differences fuck me over, I will be upset.

Secret option C there is a logical explanation as to why the cave is that deep

You go too far!

And that 'logical explanation' has no real world equivalent, making it only as real as fictional elements in the setting. Option B.

Usually if the PCs ask a question they shouldn't know the answer to yet, you can deflect it by saying something like "hmm yeah, that IS wierd, isn't it?", which prompts them to think deeper about it and want to investigate the mystery.

For anyone actually using gravity as a means to justify something like this: how many of you actually calculate how much heavier your party's gear would be in a situation like this?

I guess it's different in my groups. I always point out that the fantasy world is formed of the four elements and such, and while basic mechanical physics might make more sense, anything more complex will not. You're better off coming up with a metaphorical/metaphysical plan based on the themes and fantastical nature of the setting than applying any sort of real world scientific principle, because the latter is completely out of theme with the setting as a whole.

>doesn't need to be realistic
Maybe I am misinterpreting you but I believe you said specifically that any reason why a cave would be that deep isn't realistic, a logical explanation would contradict that

Do you think slapping 'logical' on something fantastical magically makes it realistic?

I mean in this case a cave collapsing because the weight of the overhead rock and earth is basic mechanical physical

No? If the caves are a matter of thematic and metaphorical significance, then that is more important in context. And, given the given example was the underdark, this absolutely applies.

The explanation doesn't have to be fantastically magical, simply shifting the composition of the planets crust could create deeper caves for example

>Dorfs gonna dorf
>wiped out by whatever they dug up
>while the buildings and such are all pulverized to dust by the angry whateverthefuck, the dwarven mastercrafted tunnels and great halls stand the test of time

>replace dorfs with your great race of choice

Which still leads to the problem of: how many of you are actually causing your PCs to feel the effects of increased gravity this much closer to the center of their planet?

Trying to come up with serious answers to these kinds of questions only invites more questions. At some point you are going to have to settle for a hand wave.

Sorry if I misunderstood your post, my point was that a cave collapsing to due to much weight was basic enough physics that it's kind of a head scratcher as to why the underdark hasn't collapsed, not that this can't be ignored in favor of theme and coolness

I'm saying that, by the very nature of the world, the thematic relevance and significance of Underdark can be the actual, in universe reason why it hasn't collapsed.

Actually as you get closer to the center of the planet you experience less gravity, that and questions like these can lead to good world building, I can understand if that's not appealing to you though

OK, that's actually pretty cool, this kind of makes me want to run a game where in universe theme tone and storytelling tropes are the main laws that govern reality

May as well work out the kinks in my setting
1/2

Prana is the primordial element from which all others are made. It is also know as life-force or soulstuff, because souls are self-contained and organized acumulations of prana. Any and all sentient beings have souls*, while animals have proto-souls. Having a soul in the first place demands that something has its own name, making it distinct enough that it may acquire spiritual links with other soul-possessing beings. Such links are called "ley lines", happening whenever one develops feelings of any kind upon something**. Prana flows through ley lines***.

The planet in question qualifies. Known as Ghara by most of its inhabitants, all of which either developed strong feelings upon it. Fondness of one's homeland, hating a war-torn kingdom, wishing to conquer your neighbors' lands, all this makes a ley line ultimately connected to the planet itself. The daily routine of one billion soul-possessing mortals sustains Ghara's Soul, which is further strengthened by being worshipped as a earth-goddess/father-god/Land Spirit by most of them.

Gravity is not an effect of mass, but of prana. Ghara's Soul is the greater concentration of prana other than the Sun. Its cosmic purpose is to make itself suitable for the living of soul-bearing creatures. Its own survival also depends on having souls linked to it.

That's why gravity is uniform throughout the crust: more living space to eventually house soul-bearing beings. Dwarfs are the most common example of this.