Beneath the familiar realms of Dungeons & Dragons lies Underdark – a dangerous and scary setting fit only for the bravest of adventurers. This vast underground realm is made of interconnected tunnels and caverns that can stretch along whole continents. It has its own unique ecosystem, geography, and inhabitants that lurk in the shadows just waiting to pounce on an adventurer that strays away from the group.
Underdark originated all the way back in 1e and was present in many campaigns, fiction books, and sourcebooks since. It has even found a place in the 2023 DnD movie – Honor Among Thieves.
Whether you’re a DM looking for a spooky setting for your next adventure, or a player wondering what lurks beneath the surface, this guide will take you through everything you need to know about this perilous world. We’ll go through the lore of Underdark in DnD, the monstrous creatures that call this place their home and even list a couple of example encounters to inspire you to create your own.
So, grab your torches, gather your courage, and join me as we step into the unknown!
Environment of Underdark
One important thing about the Underdark is that you have to expect the unexpected. The environment of this subterranean realm is vastly different than the one you’re used to on the surface.
Instead of looking up at the sky, you’ll have the pleasure of gazing at the cavern ceilings. The terrain is also very jagged and uneven – there are underground fungi forests, lakes and rivers, winding tunnels, and colossal caverns. Stalactites and stalagmites are jutting out from the ceilings and floors everywhere you look. Some places are huge, and you will have to squeeze through the others.
Also, there’s a reason why this place is called the Underdark – it has little to no light. The only light sources are bioluminescent fungi or glowing crystals, but even then – the glow is dim and eerie.
Because of the large quantity of water, there’s tons of moisture in the air, making it perpetually damp, stuffy, and hard to breathe. You can encounter potentially explosive gases or even lava if you venture deep enough. There’s tomb-like silence in the caverns, but if you do make loud noises, they will echo and alert every nearby creature that dinner is ready.
The resources are scarce, the creatures want to kill you, or eat you, or both, and the haunting and otherworldly atmosphere will make even the bravest adventurer feel trapped making the Underdark a perfect setting for a survival-heavy, intense campaign.
Creatures of the Underdark in DnD 5e
Now, let’s go through some of the creatures that will wait for you when you descend into this scary realm.
No sunlight in the Underdark means no plants which also means that you won’t get a lot of herbivores down there. The only food available is fungi, other creatures, or a stray adventurer, so you need to be super vigilant in order not to get eaten. In spite of all these adversities, there is a wide array of creatures that have adapted to these unique conditions.
Drows are probably the most well-known creatures that inhabit the Underdark. These malevolent beings are the black sheep of the elf family. Also the evil sheep. They are skilled in combat and spellcasting, are very intelligent, and live in elaborate subterranean cities.
There is also a notable population of gray dwarves – duergar – in the Underdark. They are best known for their psionic abilities. Also, their tendency to enslave species they deem inferior to them.
As further nightmare fuel, you have sentient fungi, spider-like monstrosities, insectoid creatures with hook-like appendages and so many other bizarre creatures that pose a unique challenge for adventurers.
And if all of this isn’t scary enough, there are mind flayers, aberrations with octopus-like heads that possess psionic abilities and feed on the brains and other creatures, and beholders that are considered one of the world’s biggest threats.
These are all great monsters you can use in your campaigns, but there are so many more out there just waiting for your players. If you need more examples, check out Volo’s Guide to Monsters, Mordekainen’s Tome of Foes, or Mordenkainen Presents: Monsters of the Multiverse.
How to Get to the Underdark
If you’re still stupid…I mean..brave enough to visit the Underdark even after I’ve told you what to expect in this world, then you will need to know how to actually get there. There is typically no Underdark Express, but there are still quite a few options available to a party of adventurers.
There are some natural entrances where the surface world and the Underdark connect via deep chasms, caves, sinkholes, or even abandoned mines and dungeons. You can also look for an already existing portal or magical gateway, try a dark ritual, or if you have a super powerful spellcaster – planar travel is an option too.
The method you choose will depend on your campaign setting and the story your DM wants to tell. If a group of players really wants to venture into Underdark, a creative and willing DM can find a clever way to integrate that into the existing campaign.
Versions of Underdark in DnD History
As I’ve previously mentioned, the Underdark has very deep and intricate lore in the DnD universe. This underground world has also been known by many different names: the Underworld, Underrealm, Night Below and Deepdark are some of the examples, but the Underdark has become the most commonly used term in recent editions of the game.
Some notable appearances of this world in DnD are:
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In fiction books by R.A. Salvatore – The Icewind Dale trilogy and the Dark Elf trilogy
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Vault of the Drow – a classic 1e adventure module that takes players into an Underdark city
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Drizzt Do’Urden’s Guide to the Underdark 2e
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Underdark sourcebook for 3e
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Out of the Abyss – a 5e Underdark adventure for levels 1-15
These are just a few examples and there are numerous other DnD publications that are set in or can teach you more about this dangerous, but iconic campaign setting.
Underdark Encounters
As you’ve probably gathered by now, the Underdark offers endless possibilities for thrilling encounters in DnD 5e. So, in this section, I’ve prepared a little collection of example encounters that you can drop in a campaign exactly as is or modify to better suit your narrative. Whether you’re looking for a tense combat situation or an encounter that will make players flex their role-playing skills – you can find inspiration here, so let’s go through them all!
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The party steps crawls into a large cavern and they trigger a shrieker. Suddenly, 2d4 cloakers descend onto them and attack.
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The party is ambushed by drow raiders in a narrow, winding tunnel
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The party sees a drow patrol in the distance. If they don’t manage to camouflage themselves or hide, and they get seen – the patrol will take them to a jail cell.
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The characters encounter a duergar caravan that is transporting various creatures to a nearby city. The party can choose to attack or try to free the prisoners.
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The adventurers enter a fungi-infested area and step on some fungus that releases a poisonous gas
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The party encounters 2-5 giant spiders feasting on the corpses of slain adventurers
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The PCs see an abandoned necromancer cult lair. Inside there are ghosts or the cult members and the unlucky adventurers that have wandered in. The players will have to solve puzzles, avoid traps and, lastly, fight the undead necromancer lord.
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The adventurers trigger a cavern collapse trapping them in a small cavern with water slowly trickling in and no visible exit
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A group of deep gnomes for help in a rescue mission
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The adventurers stumble upon a hidden marketplace in an underground city. They can interact with merchants, haggle for goods, gather information, or even find a new quest.
Final Thoughts
Now that you’ve learned about the sinister environment of the Underdark and all the horrifying creatures that inhabit it, I hope you are inspired to create your own adventure set in this dangerous world. The Underdark is a realm that puts an emphasis on bravery, cunning, and resourcefulness, and it promises adventures that will be remembered forever.
