Avernus

Avernus was the first layer of the Nine Hells of Baator. The most likely beachhead for any attack by demon-kind, it was 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.

Description
It was a charred wasteland of vast plains covered in rubble and the occasional line of foothills and mountains heaped with broken rocks.

A blood-red light suffused the very air and huge fireballs flew at random through the sky, occasionally impacting and exploding wherever they hit. Travelers needed to get to shelter like a building or cave, lest they inevitably be struck.

As with all the lower planes, the River Styx ran through Avernus, with a number of offshoots and falls. Rivulets and streams flowed across Avernus's plains, and fed the Styx. The source of this blood was not known; devils claimed it probably came from all who'd died on Avernus.

Government
The ruler of Avernus was titled the Lord of the First. This position was once held by Zariel, who was betrayed by Bel, who was then supplanted by Zariel again by the late 15 century DR. Bel was demoted by Asmodeus and made her advisor. She resided in a soaring basalt citadel. When he ruled, Bel dwelled in his own fortress at the center of the Bronze Citadel.

Activities
Legions of devils dressed in mail stood an eternal watch on Avernus, in readiness for a sortie in the Blood War.

History
As an archfiend, Tiamat was given rulership of Avernus by Asmodeus. Her job was to prevent outcast devils on that layer of Hell from becoming a threat but performed so poorly that Asmodeus demoted her. Knowing her failure was not deliberate (by reading her thoughts), Asmodeus deigned to allow Tiamat to remain in Avernus unpunished, and even gave her a chance to regain her position if she impressed him in her new role as the guardian of the main gate to Dis.

This state of affairs lasted until 1346 DR when Tiamat was elevated to status of a demigoddess. Some time after the Spellplague, Asmodeus offered Tiamat the rulership of Avernus once more. However, to avoid disappointing Asmodeus again and to prevent a conflict with Bel, Tiamat refused, instead offering to be Asmodeus' champion and devouring all who opposed him (and offering covert aid to Zariel to prevent Bel from becoming too powerful). Avernus was then by Zariel, until she was inevitably betrayed by Bel, a pit fiend general waging the Blood War and not one of the Dark Eight. He was Lord of the First by 1372 DR. Bel's minions whispered that he kept Zariel prisoner deep within the Bronze Citadel and drained her of her hellish power, slowly turning her into a soul shell while he enhanced his might. Lacking the support of the other Lords of the Nine, bar maybe Asmodeus, Bel's could advance no further, at least for the time being.

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 citadels to muster the devilish forces.

Some time later, Bel fell out of favor with Asmodeus for his inability to successfully repel a demonic invasion of Avernus. Zariel reclaimed her title as Lord of Avernus following Bel's demotion. He was forced to serve as Zariel's advisor and remained one of her chief lieutenants, waiting for her reckless tactics to lead to a mistake, so he could claim his title back.

Notable Locations

 * The Bronze Citadel: A huge fortress-city dozens of square miles in extent and ringed by twelve heavily defended walls. It housed hundreds of thousands of lesser devil troops and war machines. It was constantly being added to in the form of new fortifications against attacks. The Lord of the First reigned from here.
 * 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. A massive cave mouth near the base of the Pillar of Skulls led into Tiamat's Lair; from here, she could guard the crossing to Dis against demon attacks.

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

Connections
An especially high metal spire of Dis, the plane below, skewered trough the haze between layers and emerged in Avernus near the Pillar of Skulls. Its spiral stairwell let devils and petitioners cross on foot between the layers, with many falls, by chance of otherwise.

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.

Behind the Scenes
Avernus was an ancient name for a volcanic crater located near Cumae, Italy which the Romans believed was the entrance to the underworld.

Connections
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