World Axis Model (Variant)
Parallel planes were strange reflections of the Prime, formed by the will of the primordials in the age of creation who gathered what they considered to be imperfections of the Prime and created new planes from them. Parallel planes were the closest of the planes to the Prime and resembled it geographically, though they were very distinct in their own manner.
The Parallel Planes are:
The Feywild
A vibrant twin of the Prime, the Feywild was the home of the fey and was filled with vitality and powerful arcane magic.
The Shadowfell
A dark and twisted echo of the Prime formed by Shar from the Plane of Shadow and part of the Negative Energy Plane, the Shadowfell was the home of shadow creatures as well as much of the undead that filled the planes.
The Transitive Planes are:
These planes had little in common, except for their most common use: getting from one plane to another. A great number of spells that allowed travel from one plane to another briefly send travelers through one of the transitive planes before they reached their destination. Since the Spellplague the use of the term transitive plane had fallen out of disfavor, though the name's meaning still applied.
Astral Sea
The Astral Sea served as a transitive plane between the astral dominions, much as it did prior to the Spellplague, though now the dominions drifted freely.
Elemental Chaos
Similarly, the Elemental Chaos allowed travel between the elemental realms.
Shadowfell
The Shadowfell, in addition to serving as a strange and dark echo of the Prime also was a stop for many planar travelers. Most commonly this purpose was served for the recently dead, who passed through the Shadowfell on their way to judgment in the Fugue Plane.