The ambient field of magical energy that permeates the world, in a way analogous to both Earth’s magnetic field and its atmosphere. Aether travels across the world via ley-lines, invisible currents of magical energy, where it innervates the surrounds and allows magic to be performed. Areas with no ley-line connection are called Greylands and are generally shunned by most denizens of the world.
Following the Calamity, the Aether was destroyed but was returned to the world during the events of the Rekindling. Much like the world’s atmosphere, fluctuations in density of the Aether can be detected by arcanologists using highly specialised and sensitive equipment. This has not really led to much use, however.