In 2333, Mercury's resources were on the verge of depletion. To avert a resource crisis, humanity had no choice but to explore other star systems.
Some strange meteorites were brought back to Mercury. The peculiar energy they released gradually changed the composition of the air, causing countless Mercury organisms to mutate and attack humanity.
The meteorites brought back also grew into a beast nest, from which huge numbers of mutated beasts poured forth. Human society immediately fell into chaos, and the three sides began a prolonged war.
Humanity did find a way to grow stronger, but caught between the mutated beasts and Mercury's mutated life forms, it held out for seven years before finally losing.
To survive, humanity abandoned the land. A small number of people moved to enormous flying craft built on a temporary basis, where they continued to resist the invaders.
The airborne bases still in flight were all given the name
