Magic comes from the Aether. In order to wield magic a person must first gather enough aether and then bend it to their will. To gather the aether is called channelling and to bend it to one's will is called weaving.
The Aether is unlike anything else known to exist. It has no mass or weight, yet it can ebb and flow like the water in the ocean. The aether can be wild and chaotic or it can be still and peaceful. It can be dense and heavy like sheets of wet snow or it can be light and gentle like a feather on a mild summer breeze.
The Aether exists everywhere on Aua. Its characteristics are to a certain extent determined by its geographical location. The overall stability of the Aether seems to be a function of the distance to the equator. Close to the equator the aether is chaotic and volatile; southern magic is unpredictable and dangerous and needs to be channelled slowly and carefully to minimize the risks. Further north, close to the pole, the Aether is reliable and calm, almost solid. Northern magic is crisp and precise but great strength is required to be able to channel even small amounts of aether.
Similarly the density of the Aether seems to be a function of the distance to the centre of the planet. With higher altitude the Aether becomes less dense and above a certain point it simply stops.