Sky Whale Oil

Sky whale oil is the backbone of modern society. It is harvested from the many different species of sky whale that roam the skies of Ulaan. It functions as a fuel for modern technologies such as airships, lighting, and textile machinery. It is also the main ingredient in almost every magic potion made by alchemists.
  The whale oil functions as a hyper-condensed battery for magical energy. Potions are made by adding prepared spell ingredients, and the whale oil acts as the catalyst that makes the magic possible. Other natural conduits for magic exist (like the fruit of the Bovine Cactus), but none are as powerful as sky whale oil.
  Much like the whaling industry of the modern 16-18th century, it is incredibly dangerous and involves hunting gigantic flying creatures for their fat. Many worry that the overfishing of these whales may lead to an ecological collapse and cause oil prices to skyrocket.