Realm of the Heavens
Castus is a twin-sunned realm comprised of scattered clusters of asteroid-like landmasses supporting a myriad of photosynthetic life. These floating islands support entire isolated ecosystems and cultures dominated by winged creatures, both sophontic and otherwise, that lay claim to the endless skies. These lords of wind and sky have learned to traverse even across the Great Empty; nothing but the captured light of Ebb and Sha to fill their sails.
Having no landmasses large enough to be considered continents, the inhabitents instead organize the landmasses of Castus by Clusters. The largest of these Clusters, known as Eave, is home to the largest civilization of the realm.
While gravity exists to pull you down, it seems that the bottom of the realm just leads to the top. This means you can fall endlessly through the sky through both day and night. In Castus, the suns do not go down but instead stop burning for two days before reigniting for six.
Angel-like Manfolk. Lots of bird-like creatures. Skylight Elementals that hunt the living. Massive, sophontic whales that function as traders.
Some clusters sustain forests. There are unique flowers that are so light they can float along the winds endlessly, spreading across the realm. Some plants hang off the floating islands collecting birds for food.
Thousands of species of birds. Unique creatures that can survive off sunlight alone. Burrowing creatures that make nests of clusters. Giant spiders that spin webs to hold clusters together.
At the center of every floating island is a solid orb of pure Glow. These orbs, when removed, cause the islands to fall apart but allow spellcasters to have a small, but near endless supply of Glow that only requires sunlight to regenerate.
One sun supplies Primal Light and the other Primal Fire. Primal Air can be found in clusters floating around like clouds.
Cloud-harvesting skyships are required to supply enough water to support the growing civilizations on Castus. Massive windmills make sure that labor requirements are low. The people of Castus have little knowledge of forging.