World Axis

The World Axis Cosmology is a multiverse set-up that replaced the traditional Great Wheel in Dungeons & Dragons 4th edition.

As the name suggests, the World Axis cosmology is divided into three "layers"; the Astral Sea, "The World" (which combines the Prime Material, the Feywild and the Shadowfell), and the Elemental Chaos.

The World Axis was created when The Primordials arose in the Elemental Chaos and sought to use the barren expanse of planar space between the Chaos and the Sea as a playground, scooping up elemental matter and shaping it into the proto-realms of the Prime Material, the Feywild (from the matter that was "too bright") and the Shadowfell (from that which was "too dark"). Afterwards, the first gods descended from the Astral Sea, stabilizing the World and giving it things like life, time, seasons, and other forms of order, in contrast to the eternal flux it shared with the Elemental Chaos.

This resulted in the Dawn War, when the outraged Primordials attacked the gods for messing around in their sandbox, only to be ultimately defeated.

Specific realms of editions past became locales in this cosmology; Baator, for example, is one of the planets that floats within the Astral Sea.

Fourth Edition was controversial for a number of reasons, and this was one of them. No one would argue that this cosmology is necessarily bad, even if it was a bit derivative. But it was a "change for change's sake" rather than something that came about because of burning needs on the part of the playerbase, and grognards who liked the old system hated it. The best ideas in it were quietly glued onto the old continuity in 5e, but much less of it survives in its present form.