Claudia is a fluorescent blue ore mined on the floating world of Prester. It is the foundation of Prester's technology, fueling steam engines and is a key element of the claudia units that allow vanships to fly.
Claudia is the primary currency of Prester. It is well suited for the purpose, as it is constantly generated by Prester and is not possible to counterfeit. A frugal person will spend less than 80 Claudia on room and board in 1 week. It is also potent in its refined state, several billion (do note, that when Alex gave the stone over to the auctioned man, he stated it is not worth "nearly that much" in reference to only one billion Claudia. Meaning this fist sized stone is not possibly worth close to a billion) Claudia is only a fist-sized stone.
Primary uses for Claudia are that of fuel and the operating fluid in a claudia unit.
Claudia Fuel (Claudia-Alcohol solution)
Dissolving Claudia in alcohol dramatically increases the energy density of the fuel. This is why steam engines are the predominant technology of Last Exile, instead of the internal combustion engine. Technology design documents from the production of the show indicate that the steam engines of Last Exile have a power to weight ratio exceeding that of a modern gasoline fueled internal combustion engine.
Guild ships are shown to use a higher grade of Claudia fuel, utilising unknown methods of processing in its production. Non-guild steam engines are seen to experience a much higher performance when using this fuel.
Claudia Fluid (Claudia-Water solution)
Claudia, when dissolved in water, serves as the primary drive fluid in a claudia unit. When Claudia fluid is heated and compressed, it generates lift. A vanship engine has a distinctive claudia circulation pipe loop, where the supercritical fluid generates both lift and thrust.
Claudia-Lithium-Air battery (Claudia-Lithium solution)
Newest Vespas uses Claudia-Lithium-Air batteries as power source and Claudia-Lithium solution which lowers fuel consumption 3 times.