Lux (ルクス, Rukusu)

Lux (ルクス, Rukusu), sometimes written as Lukuss, is the city in which all main characters live. Lux is presented as the dumping site of the planet. Lux is a desolate city beset with urban decay. Taken even further as the series goes on until by the finale it's almost completely dark, bombed out, and littered with corpses and the frozen remnants of the Shapes. At the same time the Surface world is revealed to be almost completely depopulated, save for "ghosts" of people, because humanity has lost the collective will to live.

It's revealed near the end of the series that Lux was originally a massive underground concentration camp where the violent and undesirable elements of humanity were exiled to as the surface world constructed it's peaceful utopia. Flash forward an unstated amount of time later and it turns out that the surface dwellers actually pacified themselves into extinction, while Lux survived and thrived below ground.

Lux people were the descendants of violent humans but it seems like in time, with leaders like Keigo Oonishi, they might have converged towards the same fate as the Theonormals, creating a peaceful but dead end future. With Kano member of the Class coming to fight, the spectacle that Kazuho Yoshii wanted eventually happens. Kano explains to Oonishi how he despises the harmony that he maintains in Lux. He set out to change the city and succeeded. Kano knows the impass the Theonormals are in and wants humans to transform and evolve into the next species. The Texhnolyzation done to the Shapes is pushed to the extreme with only the head remaining. There’s no doubt that they are no longer human and are the another step to mankind’s evolution.

"Lux" is Latin for "light," yet the city itself is steeped in the darkest aspects of the human experience. By the end of the series, every last light in the city has been extinguished, leaving it in total darkness once the final credits begin to roll. In the last episode, Kohakura said this is the Ninth Annex of the reviving Hell.