After a short diversion, today I am continuing with my world-building series of posts.
In my not-so-humble opinion, planar travel should not be “normal” unless you are running a Planescape-style campaign. The domains of gods, demons, and elemental creatures should be strange locations that are shrouded in mystery. Being able to travel/survive in on another plane of existence, even for a short time, should be a campaign-defining event, not Tuesday.
Unless you are running a Planescape-style campaign, I would recommend keeping your multiverse as simple as possible. There is the Material Plane, Heaven, Hell, and those weird planes that spells interact with (such as the Ethereal Plane and Astral Plane).
That’s it. Mostly. With one little exception.
When powerful spellcasters get bored with reality, they create demi-planes that are their own personal playground. The normal rules do not quite apply there.
This is the perfect place for the spellcasters to do twisted experiments in privacy and if the players are brave / foolish to enter them, a great place to have weird shenanigans happen. However, in the world I am creating, demi-planes are incredibly dangerous for another reason.
If the Material Plane is your skin, imagine that demi-planes are blisters. Blisters are delicate and may “pop” easily, allowing unpleasant microbes easier access to infect you. However, instead of microbes, there would be horrible Lovecraftian entities entering the world to wreck havoc. Imagine a city besieged by orcs, yet the real danger is a seemingly normal doorway near the palace where the court wizard lives. If the delicate balance of the demi-plane is not maintained, the orcs will be the least of anyone’s worries.
The TL;DR version is that I want anything other than the Material Plane to be weird in every possible way. If traveling to another plane of existence loses any wonder or grandeur than I have failed as a GM.