Far beneath the relative safety of the surface world lies a darker, much more dangerous one.
A world of labyrinthine tunnels, vast cave complexes, ancient cyclopean temples to long-forgotten gods. This is the Underdark. You should not have come.
Stretching for untold miles beneath the earth, the Underdark is a deeply sinister, hostile place, home to all manner of unpleasant creatures, from the fearsome Bulette (imagine if a great white shark and a rhinoceros had a foursome with a bulldozer and a very angry mole) to the drow, duergar, and even the dreaded mind flayers.
In this guide, we’re going to break down exactly what manner of awfulness dwells in the dark beneath the world, giving you a more-or-less complete roster of nasty things with which to populate your underdark encounters before going into more detail regarding a few of our favorites.
Underdark Creatures List
Basically, all the best (or worst, depending on whether you’re a DM or a hapless adventurer) monster types are down here, from classic monstrosities and undead to the downright weird.
Much like the deep oceans on Earth, countless generations spent in horrible conditions, far away from the light of the sun, do strange things to the evolutionary process.
Many of the creatures that dwell in the underdark are festooned with too many eyes (or none at all), horrible claws, a surplus of tentacles, and a near-universal hunger for human flesh.
Everything down here that doesn’t want to eat all or some part of you is probably out to enslave you.
Usually this means drafting you into a life of back-breaking manual labor spent building very big walls to keep out, well, everything else that lives down here – or just cutting out the middleman and feeding you directly to a hungry pack of Grell.
Here’s our (mostly) complete list of everything in the Underdark that’s out to kill, rob, eat, enslave, or do weird magic experiments on you.
- Aboleth: Huge, tentacled aberrations that dwell deep within subterranean lakes, enslaving other races by means of their potent psychic powers.
- Behir: Giant, dragon-killing serpents that breathe lightning and are just smart enough to be dangerous.
- Beholder: D&D 5e’s most iconic original monster, complete with an antimagic field, randomized lazerbeams coming out of its eyes, and enough paranoia to make the boss of an assassin’s guild wince. Beholders lair in vast subterranean complexes, warp the nature of reality around them – so much so that their bad dreams can manifest monsters in the real world – and are generally considered to be a bad time.
- Black Pudding: The nastiest of all Oozes, black puddings corrode flesh, metal, bone, wood – basically everything except stone or magical steel.
- Bulette: Colloquially known as the “land shark,” Bulettes are large, quadrupedal, burrowing monstrosities that breach through the ground beneath your feet like a great white shark jumping for a seal.
- Carrion Crawler: A nightmarish mess of paralyzing tentacles, chitinous armor plates, scuttling legs, and far too many teeth. Carrion Crawlers scour putrid flesh from carcasses, infesting places where death is plentiful.
- Chuul: Survivors of an ancient Aboleth empire, Chuul are the godsforsaken result of Aboleth magical-genetic engineering. Imagine a 12’ tall lobster with a mass of writhing tentacles for a face and the ability to smell magic. Oh, and it’s really, really angry.
- Cloaker: So called because their leathery, bat-like wings resemble a long black cape, Cloakers are troublingly magical ambush predators capable of flying through the subterranean air like a manta ray swims through water. They can also make illusory copies of themselves to confuse and coral their prey. Oh, and they’re completely indistinguishable from a rock until they decide to drop on you like a 400-pound bag of nightmares.
- Cyclops: The classic one-eyed, man-eating giant with a great big club. Some of the D&D multiverse’s most committed atheists, for reasons they’d rather not go into. Will also throw very big rocks at you for fun.
- Dao: Evil earth elementals that covet gems above all else. Fiercely competitive with other Dao for who has the shiniest pile of rocks. Powerful spellcasters, but just as competent at hitting you with a big stick.
- Darkling: Cursed fey, exiled from their home plane to live out lives as thieves and assassins in enclaves beneath the surface world. Explode when you kill them.
- Darkmantle: Like a cross between a flying squirrel (aww, cute) and a squid (Oh, no no no, not cute!), darkmantles cling to the roofs of caves, dropping on unsuspecting prey as they project a wave of magical darkness around them, blinding their food to their approach.
- Death Kiss: When a Beholder has a bad dream about losing all its blood, it manifests a Death Kiss. These (quite literally) nightmarish creatures have blood-sucking tentacles covered in teeth, lightning for blood, and an insatiable desire to drink you like a Capri Sun.
- Death Tyrant: When a Beholder dreams about becoming a lich, sometimes it actually becomes a lich. They retain all of the powers that made them dangerous in life, but their anti-magic cone becomes an anti-life ray that prevents all healing and raises any creature that dies within it as a zombie.
- Deep Gnome (Svirfneblin): A pale, slender subrace of gnomes that dwell deep beneath the earth, Deep Gnomes have survived down here by the grace of their cunning and tenacity. They dwell within heavily fortified strongholds that can represent a moment’s reprieve for underdark adventurers – assuming they can persuade a bunch of paranoid, violent gnomes that specialize in using poison dart guns to let them inside.
- Derro: Another race of Underdark humanoids, the Derro resemble small dwarves and are, to a man, incurably insane. They often serve mind flayers or aboleths as extra muscle and fight bitter wars with the Drow.
- Dire Troll: A troll, but bigger.
- Doppelganger: Shapeshifters that steal the identities and appearances of other humanoids, infiltrating their societies and sowing chaos. As one of D&D’s most paranoia-inducing monsters, they can be found anywhere, so it’s really no surprise they crop up down here too.
- Draegloth: The combination of a drow and a glabrezu demon, gifted by the demon spider queen Lolth to especially loyal drow families to serve as bodyguards and assassins. Ogre-sized, with four arms, and the ability to move with near-complete silence.
- Drow: Dark elves who long ago abandoned the surface world to serve their demonic spider goddess Lolth in the Underdark. The Drow construct vast temples and cities in her name, using slave labor kidnapped from both the Underdark and the surface world.
- Duergar: The Deep Dwarves – tyrannical, warlike, gray-skinned, builders of vast cities that rival the citadels of the Drow. Held captive for generations by the mind flayers, the Duergar bought their freedom with a promise to keep their one-time masters supplied with a steady flow of slaves.
- Ettin: A foul-smelling, two headed orc-giant hybrid. Virtually impossible to sneak up on and possibly the spawn of the demon prince Demogorgon.
- Fire Giant: Brutal conquerors who dwell in volcanoes.
- Flail Snail: A large, elemental snail with five bludgeoning tentacles and an anti-magic shell. Once hardened, its trail can be cut into a substance resembling glass.
- Flameskull: Tiny undead skulls wreathed in fire. Flameskulls can cast a terrifying variety of fire-based spells and, if destroyed, regenerate within an hour unless sprinkled with holy water.
- Flumph: Literally the only lawful-good-aligned creature on this list. Flumphs resemble a glowing jellyfish propelled through the air on gusts of air. They feed by siphoning psionic energy and fill the rest of their days learning and debating matters of philosophy.
- Fomorian: Hideous, wicked, and cursed, Fomorians are terrifying even by the standards of other giants. These horribly mutated giantfolk fell from grace thousands of years ago when they tried and failed (miserably I might add) to conquer the Feywild. Now, they scratch out a miserable existence in the darkest, filthiest corners of the world. Best left alone; their ancient curse is said to be contagious.
- Froghemoth: An amphibious predator the size of an elephant with four grasping tentacles – an invasive species from an eldritch plane beyond our knowledge or understanding. Very hungry.
- Gargoyle: Malevolent earth elementals that hide among statues before swooping down to gouge their prey with sharp stone claws. Often employed as eternal guardians of temples and castles.
- Gas Spore: Parasitic fungi spawned from the corpses of dead Beholders. Hang around in the shape of an eye tyrant and explode into a cloud of poisonous spores if poked with anything sharp.
- Gazer: A tiny manifestation of a Beholder’s dreams, Gazers only have four eye stalks and alternate between mocking you in a high-pitched, grating voice and shooting you with eye beams. Beholders keep them as pets or use them to eat all the bugs and rats in their lairs.
- Gelatinous Cube: A 10’ by 10’ wall of quivering slime that devours anything in its path. Virtually impossible to spot until you’re already inside it.
- Ghast: Bloated, rotting, emitting a cloud of deadly fumes, a Ghast can bring down an unprepared adventuring party before it even gets close enough to use its teeth and claws.
- Ghost: Echoes of the dead, incorporeal and immune to all but magic and silver weapons and capable of either frightening or possessing anyone stupid enough to get in its way.
- Ghoul: Mindless, flesh-eating undead attracted to carnage and destruction. Ghouls inflict a paralyzing toxin that disables their prey, allowing them to feast at their leisure.
- Giant Centipede: Imagine a centipede. Okay, now imagine it’s about 3 feet long. Wait, why are you running?
- Giant Lizard: Huge, scaly monsters used as pack animals, mounts, and pets by drow, duergar, and other Underdark dwellers.
- Giant Toad: Dwellers in subterranean ponds, swamps, and other bodies of filthy water, with long, sticky tongues used to drag prospective prey beneath the surface. Probably worshiped as a god by the local Bullywug village.
- Giant Spider: Might as well be the mascot for all Underdark adventures.
- Gibbering Mouther: Weeping sores in the fabric of reality – a horrible combination of tentacles, teeth, and babbling madness that makes it hard to think, let alone act in their presence.
- Goblin: Small, angry, probably plotting to steal your lunch.
- Gray Ooze: Painfully corrosive slimes that are completely indistinguishable from a normal rock – until you step on one, that is.
- Grell: Resembles a large human brain, levitating on a nest of tentacles with a large, avian beak on the front. Truly upsetting. The fact these creatures hunt in packs and will try to carry off anything up to and including an Ogre only makes matters worse.
- Grick: A worm-like monstrosity with near-perfect camouflage in rocky terrain. You don’t see the tentacles and large squid-like beak until it’s much too late. Gricks hunt in packs and move like locusts through the Underdark, only moving on when they’ve eaten everything in the surrounding area or something bigger and nastier starts to eat them.
- Grimlock: Gray-skinned humans corrupted by millennia in service to the fallen mind flayer empire. Grimlocks’ eyes have long since been weeded out by evolution, and they hunt based purely on sound and smell.
- Hobgoblin: Brutal, tyrannical, warlike cousins of the goblin and orc. What makes Hobgoblins especially troublesome, however, is their intelligence and rigid martial society.
- Hook Horror: Oh, great: more things with beaks. Hook horrors are fierce Underdark predators with huge, sharp, hooked limbs they use to climb cavern walls and – you guessed it – drop on you.
- Intellect Devourer: A walking brain protected by a crusty covering and set on bestial clawed legs. Takes over its victim while it feeds on behalf of its mind flayer masters.
- Kobold: Small, incurably skittish little dragon men with a penchant for dastardly traps. Much like goblins, Kobolds are probably planning to rob you while you sleep.
- Kuo-Toa: Maybe my favorite D&D 5e race. Kuo-Toa are fish people with the power to warp reality around them as long as they really, really believe in it. They’re like the crowd at Peter Pan The Musical, if the crowd could turn Tinkerbell into a 300’ tall rampaging fish god. They weren’t always like this, and, as with most weird nonsense in the Underdark, it’s generally agreed that this is somehow all the Mind Flayers’ fault.
- Mimic: Another classic D&D 5e monster, the Mimic can disguise itself perfectly as any inanimate object – usually the kind of thing someone is going to poke at, like a suspiciously unguarded treasure chest. Get too close, and the mimic opens up to reveal rows of razor sharp teeth and some very sticky tentacles.
- Mind Flayer: The Illithids are an ancient race of psionic empire builders and remorseless brain-eaters that dwell deep beneath the earth. Once, the Mind Flayer empire stretched from one end of the Underdark to the other, but it has since collapsed for reasons unknown. Still, that hasn’t stopped the Mind Flayers that remain (not to mention the Elder Brains that command them) from scheming new ways to put the rest of creation back in its rightful place.
- Minotaur Skeleton: Big, made of bones and brutish rage. Probably guarding a labyrinth.
- Myconid: Sentient mushroom folk that communicate via telepathic spores. Not actively out to kill you but definitely take the approach that a stranger is just good compost you haven’t met yet.
- Nagpa: Thirteen cursed bird-wizard-ringwraith things cursed for their betrayal of the Raven Queen, which led to her death and reincarnation in the Shadowfell. Understandably not too keen to meet her or any of her Shadar-Kai again.
- Neogi: A small aberration with the body of a spider and the head and neck of an eel (interestingly, they’re a perfect intersection of mine and my wife’s phobias and therefore banned at my table). Neogi ruthlessly enslave any and all creatures they perceive as being lesser than they are, including other Neogi.
- Neothelid: A huge, slimy-covered worm that is the result of (surprise, surprise) Mind Flayer reproductive cycles gone horribly wrong. When an elder brain dies, the tadpoles it was using for food suddenly start exploring their new opportunities for a non-snack-based career, devouring each other until only one gigantic, murderous worm is left.
- Ochre Jelly: Yellowish oozes capable of slipping through the smallest cracks in pursuit of prey.
- Ogre: Large, murderous relatives of giants with a fondness for human flesh.
- Orc: Incurably brutish humanoids with piggy faces, protruding tusks, and a love of warfare.
- Otyugh: A huge, bulbous creature with three legs and a long, vine-like stalk on top of its body. Otyughs bury themselves in mounds of carrion, ready to grab anyone or anything that gets too close.
- Phase Spider: A regular giant spider with the ability to phase in and out of the ethereal plane.
- Piercer: A perfectly camouflaged, leechlike monstrosity that clings to cavern walls and ceilings, waiting to drop on anyone who wasn’t already eaten by a Darkmantle, Grick, Grell, or Hook Horror. Kill it before it grows into a Roper.
- Poltergeist: Invisible ghosts that throw things at you.
- Psychic Gray Ooze: The only thing worse than a mindless, eternally hungry ooze is one that can beat you to death with its brain. Also probably the result of Mind Flayer shenanigans.
- Purple Worm: Titanic, fire breathing, incredibly poisonous worms that burrow through the earth, bursting forth to devour anything in their path. The spice must flow.
- Quaggoth: Chasm-dwelling albino demon-ape things that live in brutally cruel societies throughout the deepest crevices of the Underdark. Often found in service to the Drow.
- Roper: A thrashing mass of whiplike, poisonous tentacles surrounding a single ravenous maw. When ropers shut their single eye, they are virtually indistinguishable from a stalagmite or stalactite. They represent an evolution in the usual hunting tactics displayed by Underdark monsters; rather than dropping on you from above, they use their tendrils to bring their prey up to the ceiling.
- Rust Monster: Feared by dwarven miners more than demons, dragons, or anything else, even the briefest touch from a rust monster corrodes metal into reddish fragments in a matter of seconds. To add insult to injury, the rust monster then eats your armor with you inside it.
- Shadow: Undead that take the form of animate shadows, capable of sapping the life out of you with a single touch. Wholly undeserving of such a low CR.
- Shadow Dragon: Dragons corrupted by the magic of the Shadowfell, infused with necrotic energy.
- Shrieker: A human-sized mushroom that can make a screaming noise so loud it’s often used as a warning system by other Underdark monsters.
- Spectator: A lesser type of Beholder with four eye stalks and the ability to reflect offensive spells back at the caster.
- Specter: An angry spirit that drains its victims’ life force. Unlike ghosts, which can be laid to rest by completing their unfinished business, the only way to stop a Specter is with a judicious application of offensive spells and a lot of silver.
- Spirit Naga: Spiteful, poisonous, virtually immortal snake-hybrids, Spirit Nagas are powerful spellcasters and the sworn enemies of the Yuan-Ti.
- Stirge: A small flying monstrosity that looks like a cross between a bat and a mosquito.
- Stone Giant: Quiet, reclusive and (as long as they’re left alone) peaceful giants with a great love for sculpture.
- Swarms: Whether it’s cranium rats (more Mind Flayer nonsense), insects, normal rats, rot grubs, or anything else that’s small and scuttles, the Underdark is prime territory for all things that swarm.
- Troglodyte: Primordial, bloodthirsty lizard men who love war and wallowing in filth and decay in equal measure.
- Troll: Fearsome green-skinned giants that eat anything they can catch and devour. Trolls lurk in the dark, awaiting the approach of prey. If that prey fights back, trolls also possess extraordinary regenerative properties that only fire or acid can halt.
- Umber Hulk: Terrifying insectoid scavengers that burrow through the earth in search of food. Umber Hulks also possess some latent psionic abilities, which let them scramble the minds of their prey, allowing them to get within mandible-range at their leisure.
- Water Weird: An elemental guardian bound to a specific body of water, totally invisible until it drags you down beneath the surface.
- Wraith: Powerful undead with the ability to create specters from fresh corpses.
- Xorn: Strange elementals native to the Plane of Earth, Xorn occasionally burrow through into the material plane. Their diet makes them an adventurer’s worst nightmare (next to Rust Monsters) as they feed primarily on gems.
There are a whole ton of other nasty things to be encountered in the Underdark, from insane druids to demonic armies (it does border onto the Abyssal Plane after all), but that would virtually double the length of this guide.
Next up, we’re going to take a closer look at five of our favorite types of Underdark monster and how to use them in your game.
Aboleths – Ancient Aberrations With a Sinister Plan
Older than humans, elves, and dwarves, Aboleths are actually a more ancient race than the gods of the multiverse themselves. Once, far back in the mire of prehistory, the Aboleths lurked in primordial oceans and underground lakes.
They reached out with their telepathic powers and enslaved many of the burgeoning life-forms throughout the mortal realm.
Under different circumstances, the Aboleths could very well have ended up becoming gods themselves.
However, the arrival of the gods into the multiverse and the ensuing (very one-sided) war between the old and new rulers of the planes led to the Aboleths being cast down – back into their ponds and lakes, never to truly rise again.
That’s not to say they don’t try from time to time.
The fantastic Underdark adventure Night Below features (spoiler alert) some very conniving and evil Aboleths who form the main villains of the campaign. While the adventure was originally written for 2nd Edition Advanced Dungeons & Dragons, it wouldn’t take a whole lot of work to run it – or something heavily inspired by it – in your 5e game. I’d recommend picking up the pdf for the art alone.
In short, Aboleths are a great high-CR opponent for your party, as they combine a manipulative intelligence with the fact that, when all’s said and done, they’re giant tentacle monsters.
They present opportunities for subterfuge, intrigue, horror, and a climactic boss fight in one neat, slimy package.
Carrion Crawlers, Stirges, Ropers, Cloakers, and Gibbering Mouthers – Monstrosities for Every Dark Tunnel
Honestly, even without the Mind Flayers, Aboleths, Drow slavers, and other “major threats,” just getting around the Underdark is a waking nightmare.
Everything that lives down here seems to have evolved to do three things:
- Be completely invisible.
- Hang from the ceiling waiting to drop on anything that walks underneath it.
- Eat you.
There are variations on this theme of course (some of these things are poisonous as well), but there’s nothing like a jaunt through the world below to turn veteran adventurers into a bumbling mess of paranoids who poke every tunnel roof with a stick repeatedly before walking along it.
Use all these great monstrosities like Piercers (and their bigger, nastier siblings, Ropers), Hook Horrors, Darkmantles, Gibbering Mouthers, Cloakers, Grell, Gricks, Stirges, and Carrion Crawlers to ambush, hunt, surprise, and terrify your players.
The Underdark is supposed to be a scary place, and there’s no better way of reminding players of that fact that demonstrating the “average” local fauna below is infinitely less pleasant to deal with that the occasional owlbear above.
Drow – Sentient Does Not Mean Fun To Be Around
There’s nothing like a night in a Drow prison to make the Grell nest you fell into last week sound comparatively welcoming.
The Drow are fully explored within this article here, but the gist of it is that a splinter group of high elves long ago gave up being kind of snooty good guys and went full-blown demon spider goddess-worshiping cult cuckoo pajamas.
Drow society is brutally cruel and strictly hierarchical, and it seems to revolve around a constant quest for more slaves to use as forced labor in their quest to build even bigger statues of naked spider women.
Because Drow are so varied (don’t even get me started on Driders, yeuch) and unrepentantly evil (with a few notable exceptions), they make great recurring villains for any Underdark campaign.
Out of the Abyss
Released pretty early on in the days of 5e, Out of the Abyss is easily one of my favorite adventures from the current edition. It’s got a strong opening (captured by Drow, funnily enough), great rules for travel that make the Underdark feel huge, unmapped, and dangerous, and a whole host of terrifying variant monsters. There’s also a demon invasion going on and you get the chance to fight Demogorgon while you’re 3rd level (inadvisable), so that’s fun.
Oozes – It’s Not the Heat; It’s the Humidity That Kills You
Oozes include Gelatinous Cubes, Black Puddings, and all manner of other slimes that want to slowly dissolve your corpse inside them. They’re mindless, relentless, and utterly terrifying.
We go into Oozes in detail here, but they deserve some love in this article too because of just how well suited they are to the Underdark.
Virtually all Oozes thrive in low-light, high-humidity environments with easy access to food. The Underdark is perfect for this.
Have your players started to get wise to the old “hang from the ceiling looking like a rock and drop on you” tactics employed by all the other Underdark denizens? Time to put a big old hole in the floor and fill it with a Gray Ooze.
If you pick up Out of the Abyss, by the way, there’s a great dungeon in there called the Temple of Oozes, which contains (as far as I know) D&D’s only friendly ooze, Glabbagool. He’s pretty great.
There’s also a major plot line that centers on insane, psychic Ooze royalty later in the adventure.
Mind Flayers – The Underdark’s Most Iconic Bad Guys
It really wouldn’t be an article about Underdark Monsters if we didn’t talk about Mind Flayers.
In addition to being directly responsible for the creation (or at least subversion) of many of the other awful monsters that live down here – from the poor Kuo-Toa to the terrifying Intellect Devourer – the Mind Flayers themselves are fearsome adversaries.
Mind Flayers live in colonies linked to vast brains in jars called Elder Brains. They’re independent, but also intrinsically linked to the hive itself.
They are utterly alien and merciless and want to eat your brains. Mind Flayers have some serious telepathic abilities, spellcasting, and psionic powers; if all else fails, they’ll just eat your brain.
Illithids make great villains for all the reasons the monsters above make good villains combined.
They are dangerous and dangerously intelligent like Aboleths, surround themselves with all manner of horrifying creepy creatures that drop on you from the ceiling, and build vast cities with slave labor like the Drow.
You probably have about as much chance of befriending one as you do starting a book club with a Gelatinous Cube. All ’round evil and proud of it.
That’s everything we’ve got for you on the subject of Underdark Creatures in Dungeons & Dragons 5e.
Just remember, the next time you find a mysterious cave at the bottom of a mineshaft after all the miners mysteriously disappeared – Don’t go poking around in there. Just don’t.
Until next time, happy adventuring – and stay out of the Underdark.