The Ten Hells (Sometimes called Baator) are a group of linked demiplanes that contain a variety of landscapes and climates. The native species of The Ten Hells are Devils.
History
The Hells were created over time by Asmodeus, starting with one layer, and slowly building up to the 10 layers that exist. Each layer is ruled by a powerful Archdevil.
The layers of Stygia and Cania were on the list of "possible convergence planes", noted for having the possibility of cross contamination with eldritch powers of the Underdark Old Ones.
Layers
The First Layer, Avernus
Avernus is the top most layer of Baator and serves as the primary battleground for The Blood War. Rulership of this layer is disputed over by the fallen angel Zariel and the Pit Fiend General Bel.
The Second Layer, Dis
The layer of Dis is a flat and barren plane. It is home to the Iron City of Dis which takes up a majority of the layer. It is ruled by the powerful Archdevil Dispater
The Third Layer, Minauros
The Third Layer of Baator, Minauros is an endless bog of vile pollution and decay. It is ruleded over by the greedy and wealth Archdevil Mammon.
The Fourth Layer, Phlegethos
Phlegethos is a flaming hellscape of fire and magma. It is ruled jointly by the Archdevil Belial and his daughter, Fierna.
The Fith Layer, Stygia
Stygia, the fifth layer of Baator, is a frozen wasteland. It is ruled by the imprison devi lord, Levistus.
The Sixth layer, Malbolge
Malbolge serves as the prison for the Ten Hells. It was first ruled by the treacherous Moloch, but after his failed rebellion against the Lord of the Hells, he was replaced by the Hag Countess, Malagard. She herself though would later be replaced by Asmodeus' daughter herself, Glasya.
The Seventh Layer, Maladomini
The Seventh Layer of Baator, Maladomini, is a layer filled with ruins. It is ruled by the ugly and disgusting slug lord Baalzebul.
The Eighth Layer, Cania
Cania is a layer of living cold. It is ruled by hells greatest wizard, Mephistopheles.
The Ninth Layer, Nessus
Nessus (also called Bolgia) is characterized by flaming landscapes and rivers of lava emerging from limitless plains of volcanoes. Jagged rocky peaks and steep drops into molten lakes provided a treacherous terrain for any creature without the ability to fly. For this reason, almost every resident of Nessus could fly safely around the flaming land. Asmodeus himself was the ruler of Nessus until the addition of the tenth layer, Hellmar. The Archdevil of Nessus sits on a throne in the middle of a towering, raging, fireball known as Malsheem. Malsheem contained millions of souls reaped from the Material plane in a labyrinth of chasms and peaks guarded by Asmodeus' best armies. After Asmodeus moved to rule the 10th layer, his daughter Glasya took his place as the ruler of Nessus.
Pathway to Hellmar
One gateway to Hellmar existed in the center of Malsheem. Guarding the gateway was the three headed dog known as Cerberus. The gateway itself required travelers to face their own fears, and was inscribed with the following poetry:
"To get below you'll show your worth. For if you want to see the earth Your darkest fears you must command do not run, you have to stand a chance to win and fears aswayed you'll soon Descend and go on your way."
Notable Locations
Hellmar
The original iteration of Quelmar, given to the gods to Asmodeus per a loophole in the Pact Primeval. Though the gods had all but given up on Quelmar after Asmodeus took his claim, private consort with surviving members of the realm convinced the gods to "reboot" the Material Plane, allowing Asmodeus to continue his rule over the original.
New Citadel
Asmodeus, after leaving Nessus to rule Hellmar, built a massive citadel of magma and steel for his new seat as archdevil over the realm. The citadel was built alongside a new type of devil known as an Air Siren, who sing a horrid song so unholy that the air in the chamber itself flees, creating an unbreathable vacuum in whatever room the siren sings in.
