Rilutaan: The Western Marches
As the name implies, the Nine Hells consist of nine layers of miserable, fiendish homes, populated by devils and the souls of the damned. Each layer is ruled over by a powerful devil known as an archdevil.
The layers are, in order:
The last layer, Nessus, is ruled over by an entity known as Asmodeus, who is also the de facto ruler of all the Nine Hells, though many of the other archdevils plot and scheme for ways to overthrow him and take rule of Nessus and the Nine Hells for themselves.