Avernus

Avernus was the first layer of the Nine Hells of Baator. It was a vast charred wasteland of rubble and the primary battleground of the Blood War. Legions of devils marched across its plains in continual readiness to repel the hordes of demon invaders that sailed the River Styx into the layer. A red light suffused the sky and huge fireballs flew across the layer, randomly exploding wherever they hit.

Geographical Features
A portal to Avernus was erected in the Burial Glen of Myth Drannor by banites loyal to the High Imperceptor of Mulmaster, but under the influence of Zhentarim agents and, by proxy, a cabal of alhoon living in the ruins. The alhoon had it erected so that the devils it spawned would prevent the local phaerimms from attacking the liches while they searched the city for magic.

Although the portal was closed by the Knights of Myth Drannor, the devils it had already unleashed continued to infest the ruins until the Elven Crusade led by Seiveril Miritar.

Another portal to Avernus was erected in Dragonspear Castle by a Calishite mage after Daeros Dragonspear, the castle's builder, was tricked into sacrificing himself.

Government
Zariel was the ruler of Avernus, after supplanting Lord Bel, the former lord, who was demoted by Asmodeus and made her advisor. She resided in a soaring basalt citadel.

History
Before Zariel's rule, Avernus was known to be a rich and civilized realm of cities and commerce. The Blood War reduced the entire layer to a blasted and abandoned wasteland, whose only functioning structures were military citadel to muster the devilish forces.

Notable Locations

 * The Bronze Citadel, a huge fortress city, housing massive numbers of devil troops and war machines. It was constantly being added to in the form of new fortifications against attacks.
 * The Pillar of Skulls, a hideous landmark of trophy-skulls of those killed in the Blood War. It reached a height of more than 1 mile (1.6 kilometers). It was very close to the entrance to the second layer, Dis.

Divine Realms

 * Draukari, the realm of the chief deity of the kobolds, Kurtulmak.
 * Tiamat's Lair, a tall mountain that was the prison of Tiamat in the Great Wheel cosmology. It was somehow connected to the Dragonspawn Pits of Azharul, Tiamat's main realm.

Inhabitants
Devils in Avernus were known for some common sayings:
 * "Avernus welcomes all."
 * "Fires of the pit!"