Subplanes are subdivisions of reality, balanced in favor of a particular element. When an elf or elemental uses elemental magic, the magic is drawn from the associated subplane.
The subplanes are home to the elemental spirits, sentient and nonsentient creatures. Sentient elementals, for the most part, come and go at will from their plane of origin into liminal space. Nonsentient ones remain in their element unless brought into the liminal by a sentient spirit, or summoned by an elementalist. The elements follow Japanese/western elements, earth, water, air, fire, void. The Umbral subplane is not a natural subplane, but serves as a sixth subplane, a subplane of exclusion specific to humans.
The subplanes of Earth are exclusive of the universe. Every planet has an outer veil that serves as a boundary separating the magic native to the plane from the magic native to another planet, or to the universe, or to reality. For this reason, elementals and elementalists cannot leave their planet of origin.
Subplanes have their own construction, but constructiong a structure in a subplane has disadvantages. the parts of a subplanar construction that are not part of liminal space can only be accessed by elementals of that subplane. The terrain of earth can only be changed in liminal space. Denizens of umbral space always also build in the liminal whether they realize it or not.
Subplane of Fire
Subplane of Earth
Subplane of Air
Subplane of Water
Subplane of Void
Subplane of Umbra