Demons live deep in the underworld. The underworld is a strange place: It is a cave system, composed mainly many extremely large caverns, with a few wide corridors connecting them. The ground of these caves is unusually soft and loamy, and has many relatively wide streams cutting through it. There are no trees, but instead the only plants are climbers, which stick to the high walls of the caverns, with the roots at the margins of the soil. There is also a clade of mosses, and several types of lichens. These plants feed on the radiation of the cavern walls. There are also many types of fungi and animals, including many domesticable animals with large bones, tusks, and other hard parts

While the demons have no shortage of stone, it is still expensive, and would not be suitable for vehicles, and various other things. There are also metals, which could be used in wagons and other such constructions, but are still generally quite dense, and it seems like they would generally be better used for weapons and other such things. Furthermore, neither stone nor metal are useful fuels

Out of all the materials that might be found in the underworld, what could replace wood, specifically in the realms of fuel, building construction, and things like vehicles and furniture?

  • $\begingroup$ Why do you need building construction in a cave? Generally you build a building to control the climate/protect yourself from the elements. In a cave the environment generally changes little, so all creatures living there will be adapted for the climate. It doesn't seem required to have a house. As worst you dig out a cave. They are soft and loamy, so it should be easy to do so. If you need elevators and such I can understand, but your requirements for building material has shrunk so much you can use the iron and stone you have. $\endgroup$
    – Trioxidane
    Jul 4, 2021 at 11:10
  • $\begingroup$ @Trioxidane There are still animals in the caves that would need to be protected from, and there might be cooler areas that people may want to live in, and thus would need a house to keep in warmth $\endgroup$ Jul 4, 2021 at 11:14
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    $\begingroup$ If you have mosses, liches, and vine/climber plants why don't you have trees? It seems sunlight is not an issue. Also, why is stone expensive? Your demons are surrounded with it. Any demon can just smack away with stone hammers and get building material. Answering this to your audience will help suspension of disbelief. $\endgroup$ Jul 4, 2021 at 12:29
  • $\begingroup$ All the vines I've ever encountered are quite woody. While they would be hard to use for tools, they would burn just fine. If these are not regular vines with woody stems, please specify. otherwise, pressed and dried vegetation should work perfectly well (except for chimneys & oxygen consumption, which I'll guess are bigger problems). Can these folks persuade vines to grow into curtains, walls, etc.? $\endgroup$
    – DWKraus
    Jul 4, 2021 at 22:55
  • $\begingroup$ For fuel, they'd probably use coal (or maybe coke), not wood. Coal is underground. $\endgroup$
    – Tom
    Jul 5, 2021 at 7:37

3 Answers 3


Replace wood (...) in the realms of fuel, building construction, and things like vehicles and furniture?



You could breed animals into varieties that produce blubber. That is a nice fuel. The biggest point of the whaling industry by the 1800's to 1900's was harvesting whale oil, which burns without making smoke - great for a cave system.

building construction

Vertebrate animals have bones[citation needed], and sometimes leather, which your demons could use to craft stuff and build buildings.

and things like vehicles

Horses were THE land vehicle for humans for more than 90% of our history. Saddled models were the most popular, but in most times and places you would also find makes that came with carts attached. Some vehicles included multiple horses attached to the same carriage for extra HP.

and furniture

See the part about building constructions. If you can make a cot out of it, you can make a chair out of it.

On top of that, feathers, wool and silk are great for making cushions and beddings.

  • 2
    $\begingroup$ At least within the realm of fantasy, invertebrate animals can also provide useful building materials. For example, in the video game Morrowind there is a large building built from the carcass of a gigantic crab. $\endgroup$ Jul 4, 2021 at 23:26
  • $\begingroup$ Horse domestication happened around 3500 years ago, Humans are the product of Neanderthal and Sapiens hybrids. Neanderthals were born 450'000 years ago, Sapiens 300'000 years. The first time multiple tribes gathered together to build the first ever monument was 12'000 years ago, The first city built was 7500 years ago. as you can see, it doesn't matter how you count the beginning of humanity, horses were not used for 90% of our history. Based on your own definition horses were part of 0.8% to 46% of human history $\endgroup$
    – Green
    Jul 5, 2021 at 12:54
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    $\begingroup$ @Green That's prehistory, not history. $\endgroup$ Jul 5, 2021 at 14:32

All kinds of scavenged stuff.



The underworld has portals. And it is lucky for its residents that it does because otherwise the air would be stagnant and things that breathe would suffocate. Certain of these portals produce high winds, either in or out - sometimes steadily and sometimes this will vary unpredictably. All of the portals lead to other places.

Portals offer access to these other places for the demons. This can be risky; a portal can shut, or can lead to a dangerous place. The portals are not all consistent. Some portals are pretty predictable and offer the demons opportunity to gather raw materials or scavenge / steal finished goods. The demons thus have a hodgepodge of materials and items depending on portals, availability and bravery / luck of individual demons.


Some additional possibilities to add to The Square-Cube Law's fine answer:


Organic matter akin to peat could accumulate, which could be harvested and burned. You could have types of lichen or algae that produces hydrogen or methane as part of it's metabolism, which are cultivated in catchments. And of course the vines could be burned directly.


A number of earthen construction forms could be made to work and be easier than dealing with rock. Perhaps your loamy soil hardens when fired, or when mixed with a cement analogue that can be mined in the caves.


See above. Also ropes made of vines or leather can be used for hanging furniture,


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