The Aestas setting uses a very different cosmology than the standard models found in most D&D settings. Instead of a “Great Wheel” or “Great Tree”, the alignment and location of planes are centered on the celestial objects on the skies of Aestas. The result is a somewhat simplified overall cosmology.
The world of space, time, matter, and forces known as the “Prime Material Plane” is Aestas and the universe it inhabits. The “Ethereal Plane” exists conterminously with this, underlying it in a way described by the sages and bards as “behind the stage”. It is less of a place than a transitional state which connects the material world to other planes of existence. Two other realms are directly connected to the material world, the Feywild and the Shadowfell. The Feywild is a realm of hyperreality, of light, life, and energy. The Shadowfell is a quiet, dark, somber place reminiscent of a tomb. Each is a reflection of the material world, connected to it and vaguely reflective of it in many ways. These planes together are referred to in most cultures as the “Three Worlds” or something similar. The dead are often believed to journey to both of these realms during their journey through the afterlife, but the truth is more complex than any mortal can understand fully.
Surrounding the Three Worlds is a realm of unstable reality and pure potential, known to scholars as the “Archaean Stratum”. It is a theoretically infinite realm similar to Limbo (DMG p61), in that conscious minds can alter matter and even force things into existence. Most scholars believe that the Archaean Stratum is the primal chaos from which the gods formed the Three Worlds. This is also thought to be related to how the elves shattered the third moon in the distant past. Travelers can reach the Archaean Stratum through the Ethereal Plane. Interspersed throughout the Archaean Stratum are stable pockets dominated by one of the four classic elements. Collectively these are referred to as the “Elemental Planes” though they are not directly connected to each other. These pocket realms are thought to be the source of elemental spirits, and home to various elemental beings such as the Efreeti, the Xorn, and similar things.
The “Astral Plane” is an intermediate plane that connects the “Three Worlds” to other dimensions. It is a realm of spirit where space and time are fluid and dependent on the observer and local conditions, and are largely unconnected with how such things work in the material world. It is also home to dreams, thoughts, psychic entities, and countless small pocket realms of incalculable variety. The primary use of the Astral Plane in the Aestas setting is to reach destinations tied to the moons Atoros and Quarten, or to countless other destinations.
The various outer planes in the standard D&D cosmology do not exist as they are in other settings. Instead these planes are amalgamated into two larger collectives based on their general alignments. These are each tied to one of the two moons of Aestas. The positive, “good” planes are called “Godshome” and are centered upon Atoros. The negative “evil” planes are centered on Quarten, and are simply known as “The Infinite Hells”. There are certain places in the Feywild and Shadowfell where these planes can be reached. How they are experienced depends on one’s beliefs, religious status, and other factors too arcane for mortals to comprehend. This complexity is the true reason that deities work through intermediaries… the objective reality behind it all is simply beyond mortal understanding.
Beyond all of the planes, beyond life, death, gods, and reality, lies the "Void Beyond". It is known only through the appearance and interactions with the oldest and most fearful of Maravaynha, entities feared even by the inhabitants of the Infinite Hells. Analogous to the ‘Far Realm”, the Void Beyond is inhabited by intelligences that are both vast and hungry. Only the most insane of warlocks willingly traffic with such beings.