The expansive Valeur family is a human clan of miners, laborers, and explorers. Having made a protection pact something like 600 years ago with a questionable spirit, they've been granted the ability to seek out valuable minerals, resist poison and air pollution, and live much longer than most humans.
These gifts are in exchange for a sacrifice of gold made to their protector spirit, who was an elder dragon of a now-extinct species, trying to rebuild his valuable hoard in the afterlife. o: