The City of Veil
Arcane ash is the built of residue of old magical devices, magical spells, and magical forces that have turned into a form of power. Arcane ash has been found in many ancient ruins outside of the City of Veil. The people of Veil discovered that arcane ash is what is used to power the trains, the lifts, the lights, and the illusionariums, as well as many other newly invented contraptions.
Arcane ash is highly valuable as without it, many of the amenities of the city of Veil would cease to function, especially the Clockwork, who have become the primary labor force of the Custodians in maintaining and improving the lifestyle of the Veil citizenry.
Many merchants that deal with magical items hire ash companies to go beyond the gates to find as much ash as possible. Many do not return. But those that do have an opportunity to become very wealthy.