There are numerous deadly locations and planes in the Dungeons & Dragons universe, but the Infinite Layers of Abyss always stands out among the rest. This chaotic evil plane is home to many demons, harsh environments, evil deities, and anything else that would like to kill your players.
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Running an adventure in the Abyss would be a unique and refreshing experience for both the players and the Dungeon Master. The dangers, the chaos, and the stories that can be told in the plane would create lasting memories, and with some information and tips on the plane, you will be ready to prepare for your own adventure.
7 The Way To The Abyss
If your party doesn't have access to high-level planar teleportation, you can create a story hook to send or even abduct them to the plane of Abyss. This works well if the main goal of the adventure is getting out of the demonic plane and back to the material realm.
Another approach would be to design a journey into the Underdark, and then find a portal to the Abyss or adjacent demonic planes such as Demonweb Pits, Dismal Caverns, or Nishrek as these planes have direct access to the Abyss and provide an introductory chapter for the adventure.
6 The First Impressions
What makes Abyss stand out against other evil planes, is the chaotic nature of the demonic residents of the plane. Planes like the Nine Hells while dangerous and deadly in their own way, follow laws and rules that can be rationalized and used for or against the party, but the Abyss is just pure, chaotic misery.
There's a saying among Tanar'ri, one of the most dominant demonic races of the Abyss, that says: "Ah, the infinite wonders of the Abyss. If there's anything you don't like, you'll find it here.".
This is a helpful guideline for designing the environment and the encounters for your players. Realize the characters' worst fears and describe the most unpleasant environments that they can imagine. This will not be an enjoyable experience for the characters, but there is fun for the players in overcoming these challenges.
5 The Denizens
As the home plane to demons, there will be no shortage of various demonic entities to encounter in the Abyss. The most common demonic races your players might encounter are the Tanar'ri, the Obyrith, and the Loumara.
There is much information about these creatures especially in the older editions of D&D that you can incorporate into your game, but fifth edition sourcebooks also offer many demons to fill your world with.
Unlike the devils of the Nine Hells who won't attack mortals unless they have a reason to, demons are likely to be hostile toward the characters the moment they see them. The chaotic nature of these creatures makes social interactions less fruitful, and stealth or aggressive approaches more likely to succeed.
4 Notable Locations
As the name of the plane suggests, the Infinite Layers of Abyss is in fact, infinite. This provides a great opportunity for you to design the world to your specifications.
But there are also famous locations on the plane that you can incorporate or take inspiration from for your adventure.
The Endless Maze of Abyss, created by Baphomet and populated by minotaurs, the Prison of the Mad God that holds a crazed derro deity, The Hidden Layer, the seat of demon lord Eltab, and the Realm of the Million Eyes, where the deity of beholders holds court, are some of the many locations that you can find in different layers of the Abyss. You can learn more about these locations and many more in online and published sources.
3 Powerful Beings
Demons are powerful creatures, but even among them, there are some that are feared across the planes. Many deities reside in the Abyss such as Tharizdun, Lolth, and Orcus, as well as deities of monstrous races such as trolls, ogres, gnolls, bugbears, and beholders.
There are also many powerful demon lords such as the Demogorgon, Dagon, and Juiblex. These beings might be too powerful for a direct conflict unless your characters are very high level, but they can still play a role in the overall story of your adventure.
2 Possible Social Interactions
While the Abyss is one of the most inhospitable outer planes, there are still opportunities for social encounters. Mortal travelers and captives can offer great opportunities for side quests and are one of the more common sources of social interaction in the Abyss.
While many demons are aggressive and hostile towards mortals, smarter demons might want to use a group of powerful adventurers to achieve their own goals instead of attacking them on sight. These types of demons can create tense and manipulative social encounters, where coming out with a positive outcome can be even harder than combat.
1 Story Hooks
Being abducted is one of the most common ways that mortals find their way into the Abyss, and the reason behind this can be a great story that unravels as the adventure goes on and the party tries to escape from the demonic plane. But there can be reasons for a group to decide to travel on the plane themselves.
Demons and Abyssal entities can often influence the material plane with corrupting and dangerous powers. Stopping one such influence can be a great hook for your party to start this horrifying journey on their own accord.
Discovering the source of the power and destroying it will be a heroic, challenging, and memorable path.