Cosmology

All just copy-pasta'd for now.

The world is spherical and has two moons and two suns. Scholars consider the planet to be stationary and the suns, planets and stars to revolve around it. The White Sun is the one normally in the sky, providing light during the days as normal. The Blood Sun is a smaller, blood-red sun that appears erratically in the sky, sometimes in the sky for a year, sometimes disappearing for centuries or more. The Blood Sun is not bound by ordinary day/night cycles, and follows erratic schedules when it appears, rising and setting at whatever times it chooses. The potency of magic dealing with blood and death is increased when the blood sun is in the sky.

Six planets wander across the sky: Arca, Eryl, Ilomae, Tholin, Verrin and Yrda. […]

The sidereal matrix is the energy pattern formed by the stars. The suns, moons and planets obscure, occult or enhance certain stars and constellations at different times, creating variations in the sidereal energy field and subtly affecting the world.

Notably, this causes the seasons – the White Sun's orbit moves up and down over the year, occulting slightly different parts of the sky and changing the heat and energy the sun imparts. [How about the four elemental planes co-rotate with the stars, 'behind' them? Then you get not only elemental correspondences with the seasons but also seasonal variations in planar tides and genasi births.]

[comets give some cool opportunities – omens of death and upheaval]

The elements are fire, water, air, earth, positive energy and negative energy. Each has a corresponding plane, arranged around the Material Plane at each pole. Where the planes touch, they coalesce into the para-elements: lava (fire and earth), acid (water and earth), lightning (fire and air), and ice (water and air).

The aurorae at the north pole are luminous gold, due to it being the nexus between the Plane of Positive Energy and the Material Plane. The aurorae at the south pole are vibrant black, being the nexus for the Plane of Negative Energy.

Aurorae of many different colours can occur from planar events called planar tides, where the elemental planes' natural oscillations cause them to become partially coterminous with the Material Plane. These appear in the sky as coloured aurorae. Particularly strong planar tides can cause creatures from one plane to pass to the other, or anomalous weather systems (e.g. a firestorm).

Additionally, people, animals and plants exposed to strong planar tides during pivotal stages of their development can become aspected towards that element, which is what is responsible both for elemental-aspected creatures and genasi.

The Astral Sea is known about via both magical scrying and some historical texts, but has not yet been visited. An active area of arcane research is on the ability to create portals to, or otherwise pass into, the Astral Sea.