The Formation of Hell and the Archdevils

As the energy of the Astral Sea seeped through the Elemental Chaos, some it began to interact with the Negative force of the Inner Planes. This formed formed a new realm all to itself, one of darkness and Evil, but much in reflection of Celestia it was orderly, and not in state of flux like the Elemental Chaos Plane, but rather one of order, almost as a reflection of Celestia.

What was not known to the Celests, that in the depths of the Chaotic Elemental Plane, a new Plane had formed, from the great darkness in the Negative Energy of the inner planes. A Dark hell had formed there called Baator.
  Baator was formed into 9 distinct formations of Hellish landscapes. Baator was limited in the form of 9 distinct formations of Hellish landscapes because it is so far from the Astral Sea powers of creation.
  The power from the Creation of the Celests formed Archdevils within these Hells, who competed, sometimes to the death for power over one another. It took a long time for the Celests to notice the creation of this Plane, let alone these fiendish beings of evil.