Aether

Aether is the substance that makes up the Ethereal Plane, closely studied by the vedalken and many artificers. It's properties are not completely clear, but the vedalken understand it enough to power their entire cities on the substance, and artificers have found it as a useful energy source within some artifacts. Guesses as to the source of the energy often fall into two categories. Some believe that the energy within aether stems from the celestial energy that radiates off of the souls of the recently deceased on the Ethereal Plane with no body to shield them. Other, more religiously minded, believe it is energy that gets left behind when prayers travel up to the Celestial Plane.

Properties
Aether has several main properties. One is its fantastic ability to power any machinery, best utilized in vedalken cities. It also has the strange trait seeping through any material but for brass, silver, and astral steel, and for this reason, most structures that use aether are built of one of those materials. Finally—a powerful but little known property—aether has strong addictive traits. Ingesting it is known to cure many ailments, heal wounds, and prolong life, but as soon as it is tasted, a constant supply is necessary to sustain one's life.

Aether and Vedalken
The method of extraction of aether from the Ethereal Plane is a closely guarded secret by the Aether Guild, a cross-capital guild of vedalken experts who work the machines that pull aether from the plane. Those who enter the guild all must consume constant doses of aether, to ensure both good health, and—a lesser known reason—so that any kidnapping by non-vedalken enemy will result in the death of the guild worker, due to a lack of sustaining aether.