The Night Sky, the Cosmic Structure

This world is yet unnamed, but I've got some ideas for the cosmic structure... which ultimately determines the look of the night sky.

Look into the night sky of this unnamed world, and the first thing you'll notice is its moon, which is colored differently depending upon the season... an unusual sight to be sure. This is not a thing that actually exists, but rather a reflection of the two other facets of the world: the bright side reflecting the Feywild, and alternating between a pale green, a bright green, fading through orange, and then sparkling white... the four seasons experienced by both the unnamed world and its Feywild. The dark side of the moon reflects the Shadowfell, the destination of the departed. The moon has no echo in the Shadowfell (or, if it does, its role is undefined aside from an eerie light that deepens the shadows), but it exists in the Feywild as well. Being within reach of ordinary flying, it is the location of Avandor

Look around, and at either dawn or dusk, among the stars, you can see a a bright white crescent of light. This is Hestavor-Tytherion, a body tidally locked with the sun, and hosting the Bright City of Hestavor on the light side, and the Endless Night Tytherion on the opposite. It always follows the sun, hiding behind it when Hestavor is fully displayed, and hidden by the suns glare when Tytherion is fully displayed, but the influence of each coincides with the seasons. Hestavor is behind the sun at the height of summer; Tytherion in front in the depth of winter. The days grow longer as Hestavor waxes, and shorter as it wanes.

All the other planets might be found anywhere on the ecliptic, with occasional retrograde motion.

A bluish sphere of light marks Celesta, the Heavenly Mountain. The efforts of the good and the just, and the artisans that support them, seem to receive a boost when Celesta is highest and brightest in the midnight sky.

A darker, rust red sphere marks Chernogger, the Iron Fortress. An increase in the level of warfare in the world seems to occur as Chernogger reaches its highest and brightest in the midnight sky.

And faintest, seeming to give off its own hot, malevolent red light, is the Nine Hells. The summoning of the dark inhabitants of that plane seems to be easier when it is brightest and highest in the midnight sky, thus the corruption of mortals.

Conjunctions are important events. When more than one of the planes line up, things get interesting. The battle of good and evil is especially intense when Celesta and Hell are in line, and especially violent if Chernogger is also in line. When Celesta is highest in the dead of winter (ie. when Tytherion faces), good and evil dragons tend to make deliberete war upon one another. Warfare between mortals is intense whenever Chenogger is in alignment, but if it shares space with Celesta, the good tend to see victory; if the Nine Hells share it instead, the evil tend to see victory. Woe to mortals should this occur when Tytherion faces the world... and blood runs in the depth of winter!

Basically, what I've done here is taken the planes of the Astral Sea, included the main world as an astral plane, and made them into a heliocentric solar system. The plane(t)s, from inner to outer, are Hestavor-Tytherion, The World, Celesta, Chernogger, and the Nine Hells. The Moon represents (though it isn't actually) the reflections of the World: The Feywild and The Shadowfell. When they pass nearest to The World, the influence of their inhabitants intensifies.

One could theoretically assign values to the orbital periods of the planets, and use the turning of the system as an idea generator, determing "what's the big metaplot this year? Demons? Dragons? Or a little of both?" ;-)

The planes are still infinite in nature. The three dimensions of the world are "curved". If one flies high enough, one finds himself traveling toward the world, at another part. It "feels" as if the flyer has traveled in a straight line, but straight up and straight down both lead to The World. It is the same if one diggs deep enough: the hole one emerges from is another part of The World (yes, it is theoretically possible to "dig a hole to China"). Travel far enough to one side or the other, and you eventually end up back where you started.

Planeshifting magic is needed to escape the confines of The World (its a bit like escape velocity, but the mechanism is more like a quantum jump simply a question of momentum). Shift up, and you reach the Astral Sea (which is actually a flat, glasslike "sea" in which the planes float about in their circular orbit). Shift down, and you reach the Elemental Chaos. Shift laterally, and you reach either the Feywild or the Shadowfell.