# A quick guide to the Nine Hells, v. 1.0.0
Welcome! This is a quick guide I made to myself to prepare for Baldur's Gate: Descent into Avernus, and now I am sharing it because why the hell not? (Pun intended). I hope you enjoy it!

### The Nine Hells
In the Great Wheel cosmology (PHB, pg. 303), the Nine Hells are placed as an Outer Plane. Also know as Baator, the Nine Hells are composed of nine infinite layers. The Nine Hells are home of devils, **lawful evil** fiends. They can strike bargains and sign contracts with other creatures, especially mortals, who exchanges their souls for something they desire. 

Each layer has an archdevil who acts as a ruler of the layer. These archdevils have immense power, and they all answer to **Asmodeus**, the Overlord of the Nine Hells. 


### The Blood War
While the Nine Hells are a lawful evil plane, the Abyss is ruled by chaotic evil entities, the Demon Lords (such as Demogorgon and Orcus). These planes are in constant war for supremacy in the cosmos. The fight happens mostly in Avernus (the first layer of the Nine Hells) and in certain locations in the Abyss, but it can also happens in the Material Plane and wherever demons and devils happens to clash with each other. 

The devils attack the Abyss thanks to a belief that they are the only thing stopping the demons to destroy the entire multiverse, and, to the devils, the multiverse should be thankful to them for doing this. The demons attack the Nine Hells because it is the closest plane to the Abyss, connected through the **Styx**, a dark watered river that runs throught both the Abyss and the Nine Hells. Because of this, the demons can't launch regular attacks against other planes, or the forces of the Nine Hells would attack and conquer the Abyss.

For more details on the Blood War, read the chapter one of Mordenkainen's Tome of Foes.

### The Styx

A unmappable black river, the waters of the Styx are navegable only by merrenoloths (MToF, pg. 250), who can be payed to carry anyone through the river. But getting lost is not the worst that can happen. Touching Styx's water can stun a creature, and drinking or being fully immersed in it can erase all the memories of a creature.
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>##### For more information
> This is only meant to be a quick guide (something a DM can keep opened during a session). For more details in the Nine Hells and its lords, you can read Mordenkainen's Tome of Foes chapter one, the Monster Manual entry on devils (page 66) and whatever information there is in Baldur's Gate: Descent into Avernus!


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## The Nine Layers of Hell
<div style='margin-top:140px'></div>


<div class='wide'>
##### The Nine Layers of Hell
| Layer | Name | Ruler | Quick description | 
|:----:|:-------------|:-----------------|:-------------|
| 1 | Avernus | Zariel | Wasteland, rocky terrain, magma rivers. Legions of devils and demons fight here.
| 2  | Dis | Dispater |Black, stagnant rivers extending for miles, until they reach some hills. The Iron City is in the center of this layer.
| 3 | Minauros | Mammon | A swamp made of pollution and rotten bodies. 
| 4 | Phlegethos | Belial and Fierna| Volcanoes, rivers of fire, unbearable heat. This layer resembles the steryotipical "Hell" more than any other.
| 5 | Stygia | Levistus | A bottomless, frozen ocean, with a three mile (five kilometers) thick layer of ice covering the water.
  | 6 | Malbolge | Glasya | A gargantuan tumble of angular black stone blocks, each block ranging in size from a small city to a large metropolis, that formed a pile hundreds of miles/kilometers thick.
  | 7 | Maladomini | Baalzebul | Filled with ruins of old cities, stagnant rivers, exhausted and abandoned quarries and strip mines, swarms of biting flies, and black pools of ichor that erupted from the ground. 
  | 8 | Cania | Mephistopheles | Solid ice mountains, titanic, unnaturally fast-moving glaciers, and nearly continuous snowfall that made Stygia seem balmy by comparison.
  | 9 | Nessus | Asmodeus | A rocky wasteland with deep fissures. Asmodeus stays in a fortress, located in the deepest pit of this layer.
</div>

*This table is a quick guide to all nine layers, which are detailed below.*
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# Lords of the Nine and its Layers
Each layer of the Nine Hells has a ruler. Let's introduce them.


### Asmodeus
The Overlord of the Nine Hells, Asmodeus is a cunning, smart devil. He makes sure all devils follows the Nine Hells laws and maintain their trafficking of souls. He is the only devil without a quota of souls to feel, so, instead of seducing and making pacts with humans, he focus on greater beings, like demigods. 

Asmodeus carries an artifact named Ruby Rod. He was ordered to carry it at all times by Primus (the Leader of Mechanus, embodiment of Law). The Ruby Rod is what allows devils to strike bargains with humans, and also what punishes them, if they break such a contract.

#### Nessus
The bottomless layer of Hell, this layer is devoid of activity. A rocky wasteland with fissures, this layer lacks roads, bridges and any other ways of passage. Somewhere in this layer, resides its deepest pit, with Asmodeus's fortress inside. Only a few followers and advisors know where it is, and Asmodeus relies on magic and messengers to convey his orders.

### Zariel
Zariel was an angel, tasked to observe the Blood War. This extended exposure made her thirsty to join the battle, which she did, even after being denied to do so. She eventually was overwhelmed by the devils, who took her to Asmodeus's fortress. She recovered and was instaured as the ruler of Avernus.

#### Avernus
Once a layer filled with cities and trade outputs, the Blood War transformed it in a blasted wasteland. There is fighting all over this layer, with demons and devils constantly engaging in war. There are some unexplored ruins in this layer, but you must go to the edge of it to find them (and the treasures they might have).

##### Tiamat

The Queen of Dragons also resided in Avernus. Her lair is in the top of a mountain, with hundreds of chromatic dragons flying through the skies. The demons and devils that fight in the Blood War tend to leave her alone, since she shows no interest in participating in the war. She uses Abishai (mortals who won Tiamat in life and where transformed in devils to serve her) to represent her interests in the Nine Hells, and they answer to both her and Asmodeus.


### Dispater
A paranoic arms dealer, he trusts no one. Hoarder of knowledge and secrets, he always wear an impenetrable armor of Adamantine, whose features are known only by him.

#### Dis
A flat barren plane containing little more than black, stagnant rivers, stretching for thousands of miles/kilometers until it reached some rolling hills. The sky was a cloudy dull green shot through with lightning. In the center of this plane rose the Iron City of Dis, several miles/kilometers in height and hundreds of miles/kilometers wide. 

The Iron City is located in the center of this layer. The walls of the buildings and the stones of the streets glowed the dull red of hot iron; more than brief skin contact resulted in severe burns. Prisoners of war, tormented underlings, criminals, and kidnap victims were kept in underground dungeons where their wails of woe could be heard filtering up through small vents in the iron walls. Above it all rose the Iron Tower where Dispater sat and schemed, untouchable.

### Mammon
A merchant, he is perhaps the richest entity in all the planes. He oversees the trade of souls, using his minions to collect the souls os those who haven't pledged to any specific demon and, later, assigning them to those who can claim it, always respecting the contracts and the law.

#### Minauros
An endless bog of vile pollution, decaying bodies, and rotting marsh, repeatedly drenched by rain, sleet, and hail storms. The soggy, bone-strewn, disease-ridden swampland made movement very difficult and was only broken occasionally by serpentine ridges of volcanic rock. Nameless creatures even the devils feared inhabited the swamp.

### Fierna and Belial
The Nine Hells hierarchy doesn't normally allows two creatures to hold the same position as ruler of a layer, but those two are allowed to do so by Asmodeus himself. Fierna is one of the most charismatic devils, filling the heart of mortals with emotions and desires, while Belial focuses on ruling Phlegethos. Their relationship is far more complicated and paradoxical than that of mother and son or wife and husband. They hate and admire each other and are in constant competition, but when an outside threat rises, they will cooperate do end them.
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#### Phlegethos

Filled with active volcanoes, rivers of liquid fire, molten rock, ash hills, smoking pits, unbearable heat, all wracked by tremors and earthquakes. Even the air seemed aflame and thus Phlegethos was considered to be fire-dominant. 

The city of Abriymoch was the seat of power in this realm, built of hardened magma, obsidian, and crystal in the caldera of an extinct volcano which provided visitors some protection from the elemental environment found throughout the rest of the plane.

This is where the Judicial System of the Nine Hells is centered (overseen by Belial), resolving al disputes over contracts and accusations. The Diabolical Court answered only to Asmodeus.


### Levistus

Levistus was not always the lord of Stygia. After winning a battle against Geryon, its former ruler, Levistus was frozen in an iceberg by Asmodeus. He was tasked with offering escape to the desperate, especially those who fear for their lives. This attracted a number of criminals to devote themselves to Levistus.

#### Stygia 

A frozen wasteland, Stygia is home to a lot of creatures, such as krakens, remorhazes and frost giants. These creatures do not fear the devils, making Stygia the place to go when a devil needs to sharpen his combat skills. 

The presence of creatures from the Material Plane led many to believe that Stygia wasn't always a layer of Hell, but that it was transported to it after a planet, facing annihilation, saw its inhabitants pledging their souls and their world to Asmodeus, in exchange for saving them. He did so, making the planet a new layer in Hell.

### Glasya

The rebellious daughter of Asmodeus, she rules Malbolge, the prision of the Nine Hells. She is unpredictable, bending the law without actually breaking it. Her rose to a Lord of Hell is a subject of whispered debate, since its unclear if it was thanks to her own plans or if it happened just as Asmodeus wanted.

#### Malbolge

With angular black stone blocks honeycombed with angular passages and caverns causing non-flying travelers to frequently need mountaineering skills and risk avalanches. Stinking clouds of vapor rose up from the depths and lit the sky with the color of blood, causing cosmologists to speculate that the blocks of Malbolge may have rested on an infinite sea of lava. Corroborating reports have been heard of flammable materials left on the ground spontaneously combusting.

### Baalzebul

He once ruled both Maladomini and Malbolge. Conspiring to replace Asmodeus, he put together an army and intended to strike Asmodeus, but, as the demons started to dominate Avernus and got closer to Dis, Baalzebul was forced to help in the battle. When an investigation brought light upon his attempted-coup, Asmodeus stripped him of Malbolge and enacted two laws concerning Baalzebul.

The first law was that, for every time he lied to a devil, he would be turned into a slug-like creature for a year. Covering millenials of lies told by Baalzebul, he only recently was able to return to his original form, and has never since told a lie to another devil.

The second law was that every bargain made by Baalzebul would end in disaster for the other part. That way, he was virtually unable to strike a deal with any other devil, even if they knew he couldn't lie to them, so Baalzebul is now focused on striking bargains with mortals, who know nothing about this law.

#### Maladomini

Every document in the Nine Hells is stored in Maladomini. These storages are guarded by traps and devils, and, even if a creature could pass them, they would still need to be able to locate themselves in the deep labyrinth that is formed by all the storages.

### Mephistopheles

A powerful wizard, Mephistopheles does not entertain visitors, as his main taks is keeping the entrance for Nessus safe. With the devil Hutijin acting as his top lieutnant, Mephistopheles can focus his time on his researches. He hates being interrupted, and have disintegrated devils for the slightest transgression, since those are seen as nothing more than distractions to him.

#### Cania

Cania works as a giant laboratory to Mephistopheles. Since it is a wasteland, he can unsleash tons of arcane energy without destroying anything. Dispater constantly send spies to observe it, since Dispater would hate to see Mephistopheles gathering some information that he does not possess. Some archmages, such as Mordenkainen, have also found their way into Cania, seeking arcane knowledge.


## Disclaimer and stuff
 To make this, I used the lore contained in Mordenkainen's Tome of Foes, the Dungeon Master Guide (5e) and the Monster Manual (5e). When an information was not available on these sources, I used the Forgotten Realms wikia, available in https://forgottenrealms.fandom.com/ . If you have any questions/improvements/suggestions/"hey that info is actually wrong", please hit me up on Reddit on /u/lucasmcml, so I can change it! Thanks!