Before stepping through any door, a body’d better have a quick lesson in cosmology – how else is a basher going to know where and what things are? First, it’s important to know just what a plane is. To the serious philosopher types, a plane’s a world, or a collection of worlds, that operates according to its own particular laws, including those affecting magic, gravity, and even the mortals of the place. On some of these planes, the laws of “up” and “down” aren’t the same; on others, evocation magic yields different results; and elsewhere, behaving even slightly out of line with the powers of the place makes for grim results.
Planes are either immense and infinite, in which case they’re just called planes, or they’re limited by definite borders and are called demiplanes. The exact number of planes is unknown and probably infinite, and planar travellers know of only three major categories: the Prime Material Plane, the Inner Planes, and the Outer Planes. Still, those three have more than enough space for a flaming large number of different planes.
To get around in the planar multiverse, there are three basic rules to remember. These truths pretty well describe the structure of the multiverse, so learn them well!
The Grand Design
Okay, enough philosophy. The next question is, “How does the whole multiverse fit together?” Well, that depends on who gets asked. A Bleaker will say there ain’t no scheme, while a Godsman will go on about innate celestial glory and the like. None of them will answer the question straight. Maybe the best thing to do is to get a hold of the Guvners and ask them. (Fact is, their answer’s no better than anyone else’s, but they like to put things into nicely defined categories, and at least that’ll give a clear picture.) Their answer would go something like this:
There’s three (remember the Rule of Threes?) basic divisions of the multiverse. Although they’re all connected to each other in a variety of ways, it’s easiest to picture each as separate from the others.