The Outer planes, also called the Planes of Power, were 16 planes arranged in a circle (the Great Wheel) defined mainly by alignment and surrounding a 17th neutral plane known as the Outlands.
Interconnectivity of the planes in the Great Wheel model..
It was later adopted into Forgotten Realms when they released setting books for them.
Following the Forgotten Realms Wiki, the World Axis and Great Wheel cosmological models are both used by scholars still, though the Great Wheel is what 5e specifically uses..
The cosmology outlined in the Great Wheel model contains sixteen Outer Planes which are arranged in a ring of sixteen planes with the Good-aligned planes (or Upper Planes) at the top, and the Evil-aligned planes (or Lower Planes) at the bottom..
The Great Wheel was described as a complex, comparatively cosmopolitan place in which the gods of many worlds and pantheons mingled, the beliefs of many faiths and peoples bleeding together in a set of Outer Planes shaped predominantly by the polar forces of Law, Chaos, Good, and Evil..
It was later adopted into Forgotten Realms when they released setting books for them.
Following the Forgotten Realms Wiki, the World Axis and Great Wheel cosmological models are both used by scholars still, though the Great Wheel is what 5e specifically uses..
The D&D 5e PHB (Appendix C, p
303 specifically) shows that the Great Wheel cosmology seems to be the default cosmology for 5e
Given that the World Axis contains the Shadowfell and the Feywild, I guess that 4e tended to use that one (given that I believe those planes were introduced in 4e), and the World Tree would have been used before then?
The Great Wheel cosmology model from 1 st, 2 nd, 3 rd (core D&D), and 5 th editions
Tymora 's realm, The Quarter of the Great Wheel, located on the plane of Brightwater in the World Tree cosmology model
