Deep under the City of Glass in the frozen southern land, an age-old machine called the Heart of the City radiates a power which locals call icefire. Most citizens are immune to it, but a few, always born with physical disabilities, can bend it to their will. For fifty years, the ruling Eagle Knights, who fly on the back of giant birds, have killed these Imperfects, fearing the return of the old royal family, who used icefire to cut out people's hearts, turning them into ghostly servitors.Across the border in steam-age, science-focused Chevakia, people have built barriers against the radiation, against which they have no resistance.Chevakia also harbours the old southern royal family's only surviving members, and they are planning revenge and their return to power, taking both countries to the first war in fifty years.