The Song of the Fireflies. The Song of the Fireflies, #1

High above the clouds, where empires, kingdoms and duchies drift on floating islands and air-galleys hunt the night sky, a thief is hired to steal a box that should never have been touched. Viento lives by freedom alone-until a single job entangles him with an imperial admiral, a relentless bounty hunter, and creatures that devour human souls and shine with the memories of the dead. When he learns that one of those stolen souls may belong to his grandfather, escape is no longer an option.
As alliances fracture and collide beneath the Endless Skies, Viento is forced to confront what he has spent a lifetime running from: loss, responsibility, and the cost of choosing oneself over others. In a world where no one is innocent and grief wears many faces, survival is not enough.