Baator, the Nine Hells

The Nine Hells, also known as Baator in Infernal or simply Hell or Hells, is the home of the devils.

Baator is stylised as a plane of sinister evil and cruelty. The different types of devils that dwell here obey a strict hierarchical social structure. Each continually plots to advance their position through treachery and deception. Unlike the demons of the Abyss, the devils are highly organized, with a logical and calculating nature.

The plane itself is composed of nine different layers, each of which models a differing but no less inhospitable and dreadful environment, including barren plains of ash and rock to frozen wastes of endless ice.

Inhabitants
The principal inhabitants of Baator are the devils, fiendish creatures of pure lawful evil; the most populous variety of devils are the baatezu, a race which effectively rules the plane. The devils are in a constant conflict known as the Blood War with the Chaotic Evil demons. The ultimate rulers of Baator are the Archdevils, also called Lords of the Nine Hells; each one rules absolutely over one of the layers. The current political climate of Baator was determined by a civil war known as the Reckoning of Hell.

Besides the devils, Baator is home to hell hounds, rakshasa, night hags, nightmares and other evil creatures. A few mortals live in well-defended fortresses in Baator.

Baator's petitioners are those that have been stolen or lured from the Fugue Plane by the devils sent there to do just that. Most start as lemures, though some strong-willed souls begin their devilish afterlives as spinagons, the next step up from a lemure. Petitioners can 'evolve' to inhabit more powerful bodies, if they survive and prosper long enough to do so.

The River Styx
The Styx is a dark and dismal stream that meanders through the Nine Hells. Born in a bitter lake amid basalt cliffs on Avernus, it is linked to the Astral Sea by a seething funnel of storm clouds dense enough to bear astral vessels down into the plains of Hell. It races in a reckless black torrent through steep gorges in Avernus before disappearing into a fuming cavern and plummeting down to the fetid marshes of Minauros. Slow and sluggish at that point, it wanders on a long, dark journey before emerging again in the icy sea of Stygia. The Styx then flows through Malbolge and Maladomini before it ends in the great glaciers of Cania, missing only Dis, Phlegethos, and Nessus in its travels.

Layers

 * Avernus, the first layer, is a vast charred wasteland of rubble over which the iron towers of the Dukes of Hell stand. Legions of devils march across the plains in continual readiness for the next battle of the Blood War. A red light suffuses the sky and huge fireballs fly across the layer, randomly exploding wherever they hit. The lord of Avernus is Bel.
 * The second layer, Dis, is a burning city of iron known as the Iron City of Dis. The walls of the buildings of the city radiate extreme heat, as do the stones of the streets; more than brief skin contact results in severe burns. The Archduke Dispater rules this layer from the Iron Tower, an impregnable fortress that reaches far into the sky and can be seen everywhere on Dis.
 * The third layer of Minauros is an endless bog of vile pollution. The weather on Minauros consists of acidic rain and harsh winds. The city of Minauros the Sinking is located here, so called because the weight of the city causes it to continually slip beneath the slimy waters; only the endless efforts of thousands of slaves prevents it from doing so. The kyton city of Jangling Hiter, City of Chains can also be found on this layer. Mammon the Viscount is the ruler of Minauros, he resembles a long serpent with a human torso. He rules from the centre of the city, within a huge mausoleum like structure.
 * Phlegethos is a fiery wasteland filled with active volcanoes and rivers of molten lava. Lady Fierna and Archduke Belial are the lords of this layer. Few can exist here for long without suitable protection from the extreme heat. The city of Abriymoch is composed of hardened magma in the caldera of a volcano and is somewhat more bearable than the rest of Phlegethos. Fierna and Belial reside in a palace of pure obsidian high up on one side of the city.
 * Stygia, the fifth layer is a freezing layer of cold and ice dominated by a murky ocean fed directly by the River Styx. The dark sky is constantly filled with lightning storms. Tantlin, the City of Ice, is built on a huge ice floe with a large harbor to the river Styx, and is ruled over by a huge pit fiend. The lack of any kind of law enforcement leads itself to gangs controlling much of the city. Prince Levistus rules over this layer, frozen in a giant iceberg floating in the harbor.
 * Malbolge was an endless mountain where rockslides and avalanches of boulders were common. Numerous copper fortresses provided some refuge from the avalanches. Formerly, the Hag Countess ruled from her mountain-sized boulder fortress, which perpetually rolled down the slopes of Malbolge. Now however the layer is ruled by Glaysa, the daughter of Asmodeus. The Countess grew to such a height and girth that she exploded and became the layer itself.
 * Maladomini is a barren landscape scarred by countless forgotten ruins, abandoned mines and gruesome subterranean dungeons. The city of Malagard is the layer's primary settlement. Archduke Baalzebulpresides over this layer.
 * Cania is an unimaginably cold wasteland, few living things can survive more than a few moments in an unsheltered area. Huge fast moving glaciers crash around the layer sending snow and ice up in the sky. The layer is ruled over by Mephistopheles, from his great citadel of ice Mephistar. It sits upon a giant glacier called Nargus, the movement of which is controlled by Mephistopheles himself. Inside Mephistar huge heated baths and fire warm the citadel, providing quite a comfortable environment.
 * Nessus is the ninth and deepest layer of Baator. It is of pits and ravines of virtually endless depths. The great city of Malsheem lies immediately below the layer between Cania and Nessus and is the largest city in all of the Outer Planes. Here, Asmodeus rules over the entire plane, and thus the entire race of devils.

Avernus, the First Hell
The first layer of the Nine Hells is Avernus. It is the surface of Baator's ruby orb. It is a desert of stone, pumice, and ash broken by an occasional range of low jagged mountains or a flowing river of lava. The fortresses of devils dot its landscape surrounded by the debris of countless battles. During the most fierce outbreaks of the Blood Was, hordes of demons often invade Avernus. Consequently, it is defended by legions of infernal warriors and daunting strongholds.

Unlike the deeper hells, Avernus has a sky. In the sky, sullen, roiling clouds of red and black constantly flicker and burns with gouts of orange flame. Streaking fireballs posing a significant threat to any creatures caught out in the open pelt the barren landscape below at odd intervals. The air is hot, dry and acrid, fouled by volcanic fumes.

The mighty pit fiend ruler of Avernus is Bel, chosen by Asmodeus himself for his loyalty and his military genius. Bel is a cool, calculating creature that carefully avoids the intrigues of the other lords. A circle of pit fiends known as the Dark Eight serve as Bel's vassals and councilors. Bel governs only at their pleasure, and he must constantly consider whether his actions will meet with the approval of the Dark Eight.

Avernus is also home to a number of lesser archdevils currently in disfavor, such as Azazel, Moloch, Nergal, and Raamoth. Most are deeply engaged in various plots and schemes to seize a place of true power again or at the least discredit any Lord of the Nine they perceive to be vulnerable to such tactics. Avernus is the largest and most desolate of the hells, so many outcast devils o those few damned who escape their torments hide in its barren mountains.

Some of the landmarks of Avernus are:
 * The Bronze Citadel, the seat of Bel's power.
 * Darkspine, a once mortal city that was damned for its wickedness and crashed into the First Hell.
 * Gates of Malsperanze, the cave gateway into the Second Hell, Dis.
 * Lake of Despond, a large and bitter lake, the womb and birthplace of River Styx.