Aether

From AionSource.com Wiki

In Aion: The Tower of Eternity exists a material called Aether. It is needed in professions to transform specific items but it is also also a necessity for flying. Aether is the most unique material in Atreia, and is mostly located within the Abyss, but can be found in other areas as well. Areas which are too far away from the Tower of Eternity are rarely scattered with Aether. In the worst case, there isn't even enough Aether to enable flying.