Taking a clue from D&D many fantasy worlds exhibit different planes of existence. What for?
In D&D, it’s places for the angels, demons and other critters to come from. But that is not very relevant in play. We do not usually study the lifecycle of Barbed Devil, we smite it. Of course, we can use it as locations for play, much like distinctive regions on a map. Doing so, we can use it to color our plot in ways, which might resonably be more exotic than normal places. But really, if we want a place with weird physics we could also put on the map and have a place with weird physics just right there. It’s fantasy after all. And it might arguably more interesting, too, as the neighbors then have to deal with sitting next to a weird physics place.
In urban fantasy other planes are often used differently from the D&D model. The other world is often somehow reflective of the real one. That has several functions. Firstly it can grant insight into what’s going on, which is useful in mystery plots. A place’s character and history can be shown in its reflection. Secondly it can allow for reaching places that are barred in the real world allowing the supernaturals to move in secretive ways. Urban fantasy also often has pocket places servicing the supernatural community so they can do their business apart from people.
A fourth kind of extradimensional space is travel space. You enter travel space to cross vast distances. This is done in scifi with hyperjumps or the like, in fantasy it is often depicted as a labyrinth or pathways that can be traversed. The fifth kind regularly used in fiction is more like a reflection of the inner thoughts of the people going there. They are often used to have the characters contend with their inner demons.
- Oddly flavored adventuring areas
- Backsides of reality, often showing a distorted and revealing image
- Diagon Alleys for “special” people to meet
- Tavel dimensions
- Spaces that make the traveler’s subconscious explicit
For my Rebellion setting, I do not want a great variety of other worlds. The gods left enough strongholds abandoned to have all kinds of places on the map, so no need for D&D style planes. A way to get around quickly is useful though. Let’s have travel space.
To make one I have to figure out:
- How to get in?
- How to navigate it? / How to get out?
- How does it look?
- How did it come to be?
As for the history, that can solve another problem in the same shot. The gods, at least in the central region of the world, left. Where did they go? Some like the Forest Boy or the Earth Mother discorporated in a way. Some were killed by the rebels and turned into magic items. Some left to the far reaches of the earth. But those are all rather unattractive options. Meaning the gods who were really into these courses of action, likely already did so on their own intiative. (Except the dying perhaps.) It would be nice if the rebels could offer something to the gods.
Hey, Mr. Winter. You like the world frozen over, yes? How about you take those people who want to follow you and go to when that has totally happened already?
The travel space was created when several sympathetic gods discorparted to create it. It not only leads to other places but also into the deep past. The world is several billion years old and human civilisation has been around for 10k years at most. There is a lot real estate back there. The scheme relies on not positing groups too close to now, since that might mess up history. I’m totally ripping of that one Star Trek episode here.
But since those gods and their followers already went and nothing bad had had come of that… the plan totally worked, right? Right? Tune in next time.
Anyway, the main problem with teleportation in RPGs is that you do not want characters to appear anywhere (unless you do). So exiting the travel space is only possible at preinstalled gates, which also allow entring. Those gates are often close to the abandoned divine strongholds as they used them to leave. That is useful because you can totally come out next to those interesting adventuring locations. Gates may be closed but can be opened by anyone who is not soulscraped by mentally pushing it open. They might not be obvious in closed state, though.
Entering might also be possible anywhere with portable items, which can be handed out as quest goals.
There are also the Feuerbälger (fire brats), small red-skinned fire-resistant humanoids with horns, who have the ability to open a gate at any sufficiently big fire. The leading constructor of the tavels space was the god now known as the Lord of Ashes. The Feuerbälger are his servants still and can also navigate the tunnels reasonable well. These abilities are not public knowledge. The Feuerbälger are known to reside on Red And Cursed Isle of the coast and guard the tomb of the Rebellion’s mortal leader.
The traveling space consists of tunnels that are warm, close to 40°C. Walls and ground are covered in ash or soot. You want to bring food and especially water. There are way signs posted from time to time at intersections left by previous travelers. But mostly travelers have to work with trial and error which severely limits the usage of the system. There is no widespread use among the baseline population, though that might change if viable routes between interesting places can be found.
Many tunnels are broken and blocked. And I suppose tunnels into deep time have been demolished. Otherwise that would introduce those D&D planes through the backdoor.