As a thought for clarifying things. The shifting caves are via earthquakes, cave ins, and tunnels that collapse into others.

This is much less likely to happen to caravan routes, mostly for narrative reasons.

Infinite ever shifting caves are incredibly useful to the story, being constantly lost is not. Not unless that is the story, and it should be the players who decide that.

If only through a botched roll.

Maps work by showing which turns to take, and importantly the distance between the turns, with guides on where the scouts should step. Think of it as a list of vectors and distances.

Paths may not be stable, but if you follow a guide (either a map or markings/spore trails) you should come out of the rock face roughly where you’d expect to.

Take a wrong turn, or walk around the wrong side of a cavern, and you lose the trail. Even with a map, there’s a chance of losing the trail, at which point you either have to backtrack, or start exploring randomly. This should be a result of the Scout’s tracking and or navigational skills.

Basically, this is so that players have a degree of agency in their cave diving. It’s their rolls that see them safe, not GM rolls. (GM rolls are for encounters in the caves, things that might also be traveling those infinite paths)

Leaving markings is part of what stabilizes the route, footprints and otherwise. You could magically remove such traces and no one would be able to follow the path.

This also implies, correctly that you could use stealth, careful foot placement, or otherwise to avoid leaving a trail at all. You’d still leave body heat in the air as you pass, but with magic, you could even clear that away. At which point, someone would likely need to be within visual distance to follow, otherwise at the first branching, they’d have at best a 50% of following you.

Edit; Thinking about well traveled caravan routes, they would be very difficult to disrupt. Any caravan that regularly runs that route would have it mapped, Which requires some creative mapping, but can be done. Which leads to people finding maps to all sorts of goodies in the caves.

As a note here, the winds next to a cliff are treacherous at best. Up drafts, downdrafts, and extreme lateral forces.

This generally limits travel by airship to a single terrace at a time, but clever and skilled pilots can overcome these issues, provided their airship is suitably reinforced.

I have heard tale of a legendary battle where there was enough dakka, but I don’t believe it.

Fun fact, the horizon on Earth is easily calculated as the square root of your height in meters, multiplied by 13.

Standing at the water’s edge of the Low Shore, you’ll never see the Horizon, it’s covered by clouds and rain… But it would be a hair less than 5km for the average sized adult human.

Standing on the edge of the Green Hell terrace and looking out, The Horizon is 161km out, which is not far enough to see the opposite shore line, but the Horizon is again blocked by clouds and rain, particularly the cloud wall at 100km out.

Standing on the edge of the Emerald Hills Terrace, the horizon is roughly 280km out, once again in the Low Sea.

From the Arid Steppe it’s 360km out, once again in that same region of the Low Sea.

From the Frozen Wastes, the Horizon is roughly 430km out, which puts it in the Low Sea.

And Finally, if you could stand on the Airless Wastes, the Horizon would be just over 500km out, nearly at the center of the Low Sea, but still just barely blocked by the Cloud Wall, just like every Terrace below.

That’s why I’m putting it together.

I’ll have more posts on the History, and Religions, and then move on to the various Sentient Races. Then I’ll start doing Kingdom Maps.

For a spoiler of each;

the History goes back to the earliest settlers coming out of the walls, no races are known to be native to the Canyonlands.

The gods of the Canyonlands are all Ascended Mortals. These gods often rule a territory or maybe even just a single city, within their domain, they are extremely powerful, but are no more knowledgeable about the world or its past than anyone else. There are powerful deities, known up and down the canyon, and none of them know more about the world than the average scholar.

As to Sentient Races, aside from Humans, and every flavor of Elf, Dwarf, Orc, etc., there are also Crab People who are in a constant war against the things that lurk below.

There are tiny communities of every race you want in your world, but humans outnumber everyone else several times over.

As a note here, 1000km is the distance between New York City and Indianapolis, or Paris and Vienna.

This means that the world holds as many as 40 Canyons. Some of these Canyons will be at different tech levels, and have slightly different magic density. The Structure, however, is identical between all Canyons.

Travel between different Canyons is normally impossible. The top of each Canyon is an airless, and magicless void. While caves into the walls are non-Euclidean. There are some notable Trade routes carved into the walls, tunnels that reliably connect different cities, but most of the tunnels will loop back into the same Canyon, albeit in a random location relative to the start.

It’s said that the caves have an infinite depth, and yet somewhere, somehow, they connect to anywhere. The trick is in finding the route.

Oddly, most of those who wander into a cave, come back out again in their Home Canyon, even if they somehow stumbled into another, The next time they enter the caves, they’ll likely end up home, or at least somewhere in their home Canyon. Children born within the walls have the even greater ability to reliably find their home within the caves, with no more than a week of randomly wandering the caves.

This is purely a storytelling mechanic to allow a GM to let players play in different sandboxes, while still bringing them home at the end of the day.