Instant Settlement: Caves

No light, no light...

The saga of generating random areas continues! We've moved quite a bit away from the original generator, but we aren't done yet! Today, we'll talk about using the country generator to make caves, then in two weeks we'll finally make entire worlds with it.

Now, are caves really a settlement? Sure! Animals and humanoids of all kinds live there. Particularly, we can move towards less scrupulous inhabitants like goblins, bandits, or natural predators.

Let's go!

Instant Settlement: Caves

Recently, there's been some discussion on how to make a good random cave. A cave is twisty and turny, and has passages randomly connecting its various areas.

I'm less concerned about that, actually. If the players need to go to a certain area, don't make the cave random! Use the dungeon to direct the action! Create a critical path and guide the players along it.

I'm more concerned about generating the specific cave areas and their relationship with each other. How did the cave form? What sort of inhabitants live there? Etc.

Let's start with a random roll. Well, let's start with the same roll as last time.

There we go.

Now, as for how this cave formed, we can associate the various regions between the dice in different ways:

• A region with 2-3 d4s was formed by an animal
• A region with 2-3 d6s was formed by heat
• A region with 2-3 d8s was formed by a plant
• A region with 2-3 d10s was formed by water
• A region with three different dice was formed by a shifting of the ground itself

Each region will change slightly based on its depth. If we want a particular area to feature something on the following lists, it should be at that depth.

At the surface:

• Animals could be feral humans, notorious humans hiding from the law, or cave-dwelling creatures like Owlbears or Bulettes
• Heat could come from the sun, a hot spring or lake, or an open volcano
• Plants could include tree roots, magic plants created by druids, or invasive vines and grasses
• Water likely flows through an area due to a river or lake connected to the cave
• A ground shift could come from an earthquake, but more often from a landslide, above-ground explosion, or sinkhole

A bit deeper:

• Animals feature standard underdark fare - dwarves, drow, Quaggoths, Behir, Beholders, or creatures trying to hide from all of civilization such as Vampires
• Heat still includes underground hot springs, but also includes closed volcanoes and thermal vents
• Plants no longer have access to sunlight, thus fungus, mold, and Myconids live at this level
• Water flows from underground rivers or springs, or drips from stalactites
• A ground shift at this level is likely from an earthquake, though random cave collapses can also form and destroy passageways

And at the lowest levels:

• Animals are rare, and are likely barbaric creatures such as Goblins and Duergar, or creatures accustomed to deep earth such as Xorn or Galeb Duhr
• Heat almost exclusively comes from dormant volcanoes, though deep enough the natural heat comes from the core of the planet
• Plants at this level have trouble have difficulty existing, but small microbes may create caverns by making the soil in an area unstable and forcing a collapse. These areas are more often than not filled with toxic gases
• Water at the deepest level is essentially an underground lake. With only caverns below it, a lake could be miles deep
• At this level, a ground shift could happen for any reason, though at a large enough scale you could be looking at a tectonic plate shift

The other thing we can look at is how recently or quickly an area formed. We can determine this by adding together the numbers on the dice within a region, just like last time.

• 3-7: a fast-forming or recent area
• likely inhabited by creatures
• only a few passages in and out
• water, heat, and light are controlled - usually by the inhabitant
• vegetation isn't overly present here
• 8-13: a slow forming or older area
• could be inhabited by long-standing races, or could be overtaken by nature
• plenty of passages in and out
• water, heat, and light are difficult to control, but that doesn't mean it can't be done
• vegetation has likely taken over the area
• 14+: a very slow forming or ancient area
• might have once been a dwelling but more likely long-abandoned
• many passages in and out have formed over the years
• water, heat, and light are pretty set. Changing them takes a lot of effort
• vegetation adapted to the conditions is absolutely present

So, with all that in mind, we get this:

The best part about this cave design template is that is can be scaled up or down to nearly any size. Let's try a couple.

This area was nonexistant until a recent landslide opened up a cave (1) just beneath the surface. It lead to an ancient underground spring (5) that had created a small pool (4) and some erosion, causing a nearby area of rock (6) to crumble, exposing the roots of an oak tree (7). Some bandits found the cave, and established a hideout there (2) after clearing out the gricks who had made their home near the pool (3)

 A massive earthquake recently opened the ground up (1), surprising the human civilizations that dwelt on the surface. The passages lead deep into the earth, creating a connection to the underground city of the dark elves (2) and their underground lake (4-5). Though the dark elves have explored much of the lake (4), they have not ventured into its winding cavernous depths (5), despite the legend of a tunnel (6) leading to the fabled giant mushroom forest (7). However, the elves were quick to combat the surface dwellers to protect the breeding grounds of their precious spiders (3)

To the southeast lie the caverns of the purple worms (3). Heed the advice of the many dwarven cities in the area (2): do not venture further than their borders! Though the earth has recently had many cave-ins (1), a dwarven guide can still easily take you through the dank passages of the southwest (4), through Kuo-toa territory (5) and betwixt the stoneshatter caves (6) to reach the underground forest (7) - where a magical light feeds the trees and creates life. But be warned - it is a long and perilous journey!

I hope that this was useful. Obviously, I'd love to hear about any updates to this system if actual geologists want to chime in.

What a miserable life. Who would want this?

Thanks for reading!