Convergence

[Steampunkette]

A world built not upon a planar center, equidistant from each oppositional plane, but rather on a spinning wheel nested within others, not quite perfect in it's rotations. Where each plane upon the orrery comes closer or moves farther from the world throughout the year.

Where holidays, seasons, and existence is not dictated solely by the nearness or distance from a central star, but where the world itself spirals past the various planes and from them takes on elements.

No longer is spring simply the end of winter marked by how near or far the sun, but a convergence of the planes of water, earth, and fire. And while water and earth come close, swiftly, they also veer further just as quick, leaving fire to scorch the world with summer heat and the plane of air's winds and storms.

Where Hallowed Days as Autumn rises are the result of the plane of the Dead drawing close, it's sway sending plants to their dooms and shaking the dead in their graves, giving rise to spirits. Where winter is not simply a chill in the air, but air and water becoming dominant, again, to bring cold storms and bitter frosts.

Spring's bursts of life, and lusts, are birthed by the positive energy plane which sends life itself into the world, renewing plants and harboring children...

A world where the planes and their entities sometimes cross over into our reality, sometimes abandoning their inhabitants to be stranded until the next Convergence. Where power can be drawn from the planes, rituals performed to increase the power of otherwise simple spells.

Where Genasi walk in numbers as thick as elves and hold their own kingdoms and courts. Where the dead rule the Fallen Nights in darkened manors...

What a world, Convergence would be.

[Eldan]

Eberron does that, in a lot of ways. Have you ever read up on its cosmology?

[tantric]

hint - describe it as a hyperdisk, so that you can't actually fly to another disk, or the other side, unless you can enter higher dimensions/astral.