Aether

Aether is the source of all magic in the Four Realms.

History
Not much is known about the Aether itself

Function
As mentioned, Aether is the source of magic and binds the Four Realms together. It swirls around the centerpoint of the Four Realms and supplies them with magic. From there, individuals capable of using magic "absorb" the Aether into what is essentially a magic battery or "mana pool". The individual then draws on this supply to preform magic. If this pool empties without being allowed to refill, the individual will be unable to preform magic efficiently.