In the distant future, Earth has undergone a drastic change in the environment. For reasons unknown, poisonous layers of gases permeated the land, which resulted in near extinction for mankind due to humanity's inability to adapt to the new changes. The remaining humans built a gigantic device called Basel, an environment purifier buried deep in the ground, which cleanses the air in the surrounding land and hopefully the rest of Earth as well. Civilization began to reform around Basel itself, building a city around the tower. The upper classes live in luxurious apartments at the top of Basel while the lower classes reside among the many districts built around the base and stem of the tower. For countless years, all is well, until one day the purifier inside Basel begins to malfunction.