The Black Lungs are a small group of ex-cons who had been sentenced to work a black metal mine on the Exoplanet. Lead by Jane McCullough, a former English servant who had been falsely imprisoned for theft, they distrust the system and work to provide their own form of justice to those who need it. They identify each other by possessing matching pins in the shape of a wheel. Their mining expertise has given them the advantage of understanding the labyrinthine underground passages constructed by the Exoplanet's wildlife; they use these passages to evade and infiltrate as needed. Their activities often bring them in conflict with the Bronze Brotherhood.
They are supplied and financed by Persephone Jupiter, who professes that she doesn't want to be a princess. Whether that is her entire motivation is unclear.