Two theories about the abyss are as follows:
1. The Abyss has an infinite number of layers
2. The Abyss has so many layers that they seem to be infinite
Here is a third theory.
The Abyss has but a single layer.
This layer is an eternal expanse of darkness, cut through by three lines of burning light, which twist and spiral and zigzag, but still they inexorably progress to intersect at a single point. The point of intersection blazes like a miniture sun. Enter the point. See an endless wasteland, scarred by armies of Devils and hordes of Demons. The Plane of Inifinite Portholes. Now pull back from the point, back into the blackness. Examine the three lines. Look closer. What appear to be three solid lines of light reveal themselves to be, in actuality, made up of an infinite number of glowing points of light, connected by a complex web of faint glowing strands. Look outward. See strands of glowing points growing off of the main bands. See them branching, growing into forests and clusters, forming a latice of glowing fillaments. Clusters of points can be found, with branches growing off them. An immense web of faintly glowing points extending into the endless void. Now look closer, look a single cluster of three points. Look within each.
Here is the Tripple Fold realm of Graz'zt. See the small cluster of dim points surrounding it. Each point of light is surrounded by a cluster of dimmer points, flickering in and out of existence. Look at a point where too many of the cloud of points around it have vanished, too quickly. See the point explode outward, the fillaments connecting it to other points snapping, causing other points to wink out, causing further explosions. See the cloud of dim points from the initial explosion rocketting outward, colliding with the flotsam of the other collapsing points. See them coalessing into new clusters, new points of light, forming new connections with the main latice. See this repeating endlessly, a constantly shifting web of evil and chaos.
The Abyssal Latice
On the most basic level, the Abyss is made up of miniscule, almost insignifigant pockets of stable chaos, evil or a combination of the two. The pockets exist in an endless void of seething chaos/evil. New pockets of stablility are always forming, and old pockets of stablility are always disolving.
As pockets of stablility bump into each other, they form clusters of reality. These clusters attract more pockets of stability, which, in some cases, form a thick enough shell around the core cluster so as to insulate it from the seething mass of chaos/evil that surrounds it. Interior pockets cease to disolve. As the cluster grows bigger, the pocket of stability begins to take on a shape or form, defined by the bits of chaos and evil that make it up.
Eventually, some clusters become large enough to be catagorized as sublayers. At this point, the cluster is still very unstable, and if enough of the outer shell of pockets of stablility collapses without being replaced by new pockets of stability, the inner layers will rapidy begin to disolve back into the seething chaos/evil, causing the sublayer to disolve.
Sublayers in proximity to each other begin to attract one another, coallesing into a macrocluster, which mirrors the smaller clusters in general structure, substituting sublayers for pockets of stability.
At this point, the the macrocluster becomes far more stable, as is classified as a propper layer. However, if enough of the outer layer of clusters disolve, the layer can collapse, hurling those sublayers that do not collapse outward. Sublayers hurrled from a collapsing layer tend to collide with other sublayers thrown from the collapse of other layers, and often form new layers of their own.
Proper layers both either attract or repell one another, depending on the types of sublayers that make them up. Layers that are attracted to each other strongly enough will merge, forming larger, more stable layers. Layers that repulse one another strongly enough will send each other flying in different directions. Some layers, that have the right levels of attraction and repulsion, will form constelations. Such layers are similar, but different enough to remain separate. Often, a particular constelation will contain some layers that would naturally merge with or repulse each other, that are held togethor/apart by the attraction/repulsions of the other constituent layers. Layers in a constelation are constantly moving about because of these forces
Layers within a constelation react violently to the collapse of a layer within the constelations. Such a collapse could cause the entire constelation to break apart, its individual layers shattering in a chain reaction. The proximity of so many free sublayers usually results in the rapid formation of several new constelations.
Constilations react to one another similarly to how layers do, and a constelation of constelations is refered to as a branch. When numerous branches form a constelation, it is refered to as a Tree. Three known Trees exist. The point of intersection for these Abyssal Trees is a massive proper layer that is, apparently, connected either directly or indirectly, to every other proper layer in the Abyss. This junction layer is refered to as the Plane of Infinite Portholes.
Thus, the Abyss is in fact both infinite, and always changing.
Next: An examination of various types of Sublayers and their properties.
-- is of a swirling protomatter blob of paraplanes that move, cycle, wax and wane in some kind of malign semi-pattern. [It's distinguished from Limbo in that the latter plane is so chaotic that there are no well-defined blobs, period; it's one indistinguishable mass. The dilution of Chaos by Evil is what allows one to speak of Abyssal "layers" or "paraplanes".] This explains both why the Abyss was thought of as being infinite and bounded by 666: for a while, there really only were 666 definable paraplanes inhabiting the locale known as the Abyss, but with time more have emerged/coalesced/surfaced or however you want to view it. It also means that portals from one layer to another will shift on a regular basis depending on the alignment of the two layers, and gives Graz'zt some extra flair -- his will, and his alone, is what binds the Triple Realm of Azzagrat into a single coherent unit.
Sublayers
Properties
Abyssal Layers are made up of clusters of sublayers. Sublayers vary in their properties, but certain categorical similarities exist between types of sublayer, the most common of which are identified via a system of mathmatical profixes and prefixes attached to the layer number. Some of these profixes and prefixes are displayed below.
Link Subalyers: When a sublayer disolves, the pockets of stability that make it up either disolve back into the chaos/evil that is the basis of the Abyss, or are hurled in clusters from the point of collapse. When enough pockets of stability from a collapsed sublayer are integrated into separate sublayers, a link between those sublayers is established. Pockets of stablility begin to shunt back and forth between the sublayers. When sublayers with this connection become part of separate proper Layers, natural portholes between the layers form.
Nomenclature: Linking sublayers are denoted by the +i profix added to the identification number of the proper layer it is part of, which is followed by an identification number in {}. All sublayers in a Linking set have the same identification number.
Ex: Layers 45+i{276}, 46+i{276} and 47+i{276} connect the three layer of Azzagrat via natural portholes.
Charged Sublayers: Certain sublayers are made up of greater amounts of chaos or evil. Such sublayers naturally attract sublayers of opposite charge, chaos attracting evil, evil chaos, and repelling similarly charged sublayers.
Nomenclature: Charged sublayers are denoted with either a +xa or -xa, a + denoting a chaotic charge and a - denoting an evil charge. x is a number representing the degree to which the sublayer is charged.
Next up: More sublayer types