The 90th to 100th floors of the Fissure Corridor were not standard floors.
The alchemists who were once responsible for constructing this place hollowed out these ten floors, creating an underground city over a hundred meters tall.
The city's area was about one-third the size of Union City's Undercity.
At the very center of the city stood a tall, black spire.
It was the core alchemical device used to spray the universal metal powder onto the ground level.
On Spray Powder Day, the spire would open like petals, revealing the ultra-high-pressure airstream alchemy array within.
For the residents of Black City, the spire was more than just an alchemy device. The ground surrounding it was filled with alchemy pipelines transporting universal metal powder, energy pipelines delivering energy to the ultra-high-pressure airstream alchemy array, and a large warehouse storing the universal metal powder.
