When designing the World of Yezmyr I decided to chuck EGG's 'classical' planes right out the window. Well, I did keep the Astral Plane, and the Prime Material Plane is pretty much the same as it ever was. Beyond that, however, I made liberal changes. For instance, I don't use the Ethereal Plane. Instead, one accesses other planes by following the appropriate path. Stepping in different places and crossing various 'lines' leads to different realities. In addition to not using the Ethereal Plane, I likewise don't support the concepts of the Positive and Negative energy planes, nor do I have much use for the Concordant Opposition.
Following the Astral Plane and the Prime Material Plane are the Plane of Shadow and the Nullity. The Plane of Shadow is my general purpose home for all manner of preternatural spookiness. It is associated with both the undead and negative energy in general. The Nullity, on the other hand, is where demons come from. (As an aside, none of the demons found in D&D exist in the cosmology of Yezmyr. My demons are all custom, but I'll save those details for a future series of posts.) In any case, if you were to ask me offhand what the Nullity is like, I'd tell you that it's like dereferencing a
NULLpointer: therein lies only madness and death.
These planes are followed by an infinite procession of smaller planes and demi-planes. The idea is that I should be able to create these quickly and naturally, with each ideally suited for a specific adventure—or mini-adventure. In fact, I've done just that and created a score of planes for use in future 'unusual' adventures. In addition to custom creations, I have felt free to reference some of my favorite literary realms, including, among others, Jorge Luis Borges' Library of Babel and Brian Aldiss' Hothouse, Non-Stop, and Pile/Elip. That's the beauty of the infinite latticework: there's room for everything—even stuff I decide to like in the future. I'll never run out of room.
It is important to note that there is no 'engineered' organization to these planes. There is no overarching cosmological diagram. These planes simply exist and are multiply interconnected, and that is that. Looking deeply into the details is the province of starry-eyed sorcerers. Suffice it to say that those who are armed with the appropriate knowledge (and psi-drugs) will be able to go far in the dimensional web surrounding the World of Yezmyr. But as with M.A.R. Barker's infinite latticework, one must exercise great caution, for a single misstep can lead to imprisonment, among even worse fates.