Inner Planes

The Inner Planes, like the Elemental Planes, were an artifice of the Third World, an attempt by humanity to encode the elemental powers of the titans using arcane magic far beyond the kenning of most mortals of the Sixth World and render it accessible to all with the Will to use it. Unlike the Elemental Planes, however, the Energetic Planes never resembled much resembled their intended purpose. Both are hostile to mortal life as we know it, and were suborned by the greater Principles of Good and Evil. For this reason, divine magic rather than arcane has the easiest time accessing either, though occult magic can draw them through the intermediaries of the Esoteric Domains of Erebus or Faerie respectively, and primal magic can harness the residual energies of both Principles left on the Terrestrial Sphere still.
Neither plane is known to have any "natives" nor any appreciable geography, as it is effectively impossible for any being to travel to either of these Planes and survive. There are certainly beings that are influenced by and spawned from their influence, but it is mainly felt through the Estoeric Domains they maintain a connection to. Likewise, it is unknown if either has a Thrones of Ascension within it that can be claimed, as even the gods have not yet dared (though it is said Ka-Ata-Raya wishes to claim Entropy in her mad designs). The Plane of Anima is the positive energy plane, formed around the Principle of Seed, and is just as much associated with verdant growth and plant life as it is life-giving light, and flows through Faerie in the form of fountains of radiance. The Plane of Entropy is the negative energy plane, formed around the Principle of Dust, and seems to not only connect to Erebus through a perpetual storm of scourging sand, but have some connection to the concept of time itself.