The Nine Hells of Baator is the lawful evil outer plane of existence, stylized as a plane of sinister evil and cruelty. The different types of devils that dwell here obey a strict hierarchical caste-like 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.
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, with Asmodeus of Nessus as the supreme lord.
In descending order:
- Avernus: Vast charred wasteland, connected to the Blood Rift. Ruled by Bel, a pit fiend. Entrance to Dis guarded by Tiamat.
- Dis: Burning city of iron. Ruled by Dispater of the Iron Tower.
- Minauros: An endless bog of vile pollution. Ruled by Mammon the Viscount.
- Phlegethos: Volcanic wasteland, complete with lava rivers. Ruled jointly by Lady Fierna and Archduke Belial.
- Stygia: Frozen layer of cold and ice. Ruled by (the equally frozen) Prince Levistus.
- Malbolge: A land formed with innards and bones of the Hag Countess, the layer's former ruler. Ruled by Glasya, the daughter of Asmodeus.
- Maladomini: Barren landscape scarred by countless forgotten ruins, abandoned mines, and gruesome subterranean dungeons. Ruled by the archduke Baalzebul from the city of malagard.
- Cania: Unimaginably cold wasteland, with huge glaciers racing across the landscape. Ruled by Mephistopheles.
- Nessus: The deepest layer, full of pits and ravines of virtually endless depths. Ruled by the supreme archdevil Asmodeus.
A NWN1 Multiplayer server/module that has artfully created a campaign focusing on players cooperating to conquer the 9 Layers of Hell to defeat Asmodeus, including layer specific denziens and heavy loyalty to the D&D lore.
Although NWN1, the visual depictions give an interesting and imaginative look at the enviroments unique to each layer. Pictures for the layers are screenshots from that module.