Mystaran Multiverse
by Ethan DeneaultLets look at what the D&D multiverse is, shall we? (I'm disregarding the, IMHO, apocryphal cosmology of PC1) Most of my info comes from discussions on the list, the Gold Box, WotI, and my own thoughts (as an astrophysicist).
Existence:
There exists a Being(s) known as the Old Ones The Old Ones created the Multiverse.
The Multiverse has Five Forces - Defined as Matter, Energy, Time, Thought and Entropy. These forces control all aspects of the Multiverse. (This is akin to the four fundamental forces of the RW universe - Gravity, E/M, Weak, Strong)
The Guardians of the Five Forces are the Immortal Hierarchs. Each Full Hierarch is charged with maintaining the balance of the Five, so that none gain ascendancy, and the Multiverse remains in balance.
The Multiverse is a collection of realities, much like Feynman's "Sum over all realities" theory. Each reality is equally likely, but switching between realities requires tremendous magics or technologies. (in WotI, Realities are called "Dimensions", but I'll reserve that term for something else).
Realities are defined as vector spaces in 6 or more spatial dimensions. The first three dimensions are known as "normal" dimensions, while dimensions 3-4-5 are the "nightmare" dimensions. Mortal beings can only exist in four of these dimensions, whereas Immortals exist in 5. However, a being can only perceive one less dimension than that being exists in. (i.e. mortals perceive 3, and Immortals perceive 4.)
Mortals are of two major types - those that perceive Dimensions 1-2-3 and those that perceive 5-4-3. (note, no Mortal can perceive dimensions greater than the 5th). The Former, are known as "Normals" and the latter are "Nightmare creatures". It is best to consider each type of creature to be mutually exclusive, Normals and Nightmares fear the existence of the other, and their limited perception of the other's existence is frightening to them.
Immortals exist in all 5 dimensions 1-5. Normals perceive 1-4, while Nightmares perceive 5-2. To an Immortal, the Nightmare/Normal distinction becomes unimportant, as Immortals can perceive each other fully.
Old ones perceive every dimension, but exist in their true form in only the 6th and higher dimensions.
There are no known creatures that perceive only the 2nd-3rd-4th dimensions.
There are groups of being known as the "Outer Beings" that do not exist in "Absolute" dimensionality. These beings skip a dimension, and exist in the others. For example, and Outer being may exist in Dimensions 1-3-4-5. Outer Beings may exist in the 6th or higher dimensions, but this is unknown. Outer beings may be the manifestation of errant Old Ones, but this has not been proven.
Planar Structure:
There exists an infinite number of planes in each reality, the only planes that exist in all the realities are the "Fundamental Planes". These are defined as:
The Prime Plane.
The 4 Elemental Planes
The Ethereal Plane
The Astral Plane.
The Prime plane is akin to the Universe in the real world. The Four Elements and Five Forces are in perfect balance.
Each elemental plane is ruled by a single Element. Every Force, barring Entropy, is usually ascribed to these planes - Matter and Earth, Energy and Fire, Thought and Air, Time and Water. However (and this is this author's opinion) the Five Forces are not part of these planes, and are not conjoined with them. The Forces are independent of planar orientation.
The ethereal plane is a murky "soup" in which the Prime Plane and the Elemental Planes float in. (If it can be defined that way!! :) The Ethereal is like the "Shadow" of it's enclosed planes.
The Astral Plane is the boundary of the Fundamental Planes. Beyond the Astral the planar orientation is variable among the realities. This leads to the supposition that the Old Ones created the Fundamental Planes only, and the Outer planes were created by the Immortal generations of each reality.
Immortals:
Immortals are a higher step on the evolutionary ladder than
mortals. Immortals exist as beings of pure power, aligned
with one of the Five Forces. Immortals are a natural
progression from mortality, and the best and brightest
mortals are allowed into their ranks upon proving their
worth. There are billions of Immortals, a high proportion of
which come from the Fundamental Planes in each reality, the
rest come from the innumerable outer planes of each reality.
Immortals are charged with maintaining the balance of the
Five Forces in their reality, and thus, each reality has
it's own Full Hierarchs, but there are no more than 5 in
each reality.