Overview
The "Doomsday Nuke" that annihilated civilisation 3000 years ago, didn't wipe out the entire human population. Although only very few could survive, hiding in fallout shelters, they weren't left unscathed. The survivors were let live at the cost of becoming infertile and misshapen. Nuclear winter that ensued was hitting the survivors hard. It wasn't until a millennium after the devastation, Floating Cities were built to counteract with the lethal amount of radioactivity on the Earth's surface. Civilisation thrived again on those Floating Cities.
Due to the effects of radioactivity, some of the survivors were mutated into animal-like creatures. Some grew a pair of wings (Avian), some protruded their fangs (Wolverine), some turned their skin to cyan colour (Faerie). To the best of the knowledge of the scientists in the Citadel, this was a defence mechanism shielding those mutants from radioactivity. Because of their high tolerance against radioactivity, their population quickly outran that of the intact humans. For the fear of being overtaken by mutants in the future, intact humans made the decision of building three kingdoms that hopefully could keep the mutants under control. They revived monarchism and erected three families: the Emeroses, the Seabournes and the Thatchorns.