In this walkthrough, we’ll explore the cavernous depths of the Underdark, a vast system of caves with its own ecosystems and — fittingly — its own factions and events that require some sort of intervention. Luckily for the people involved, you have this guide to help you navigate the Underdark and its many quests and secrets.
In the Selûnite Outpost, there is a large statue in the center of the room. You might have also noticed the statues outside the Outpost shooting fireballs at anything that moves (see #4). In order to disable those, all you have to do is destroy the moonstone on top of the Selûnite statue, which will disable the turrets. You might want to wait and let the turrets kill the nearby minotaur first, though.
If you have an Acolyte (like Shadowheart) in your party, then destroying the moonstone will also earn you the “Shatter the Moon” inspiration.
In order to access this chest, you will first need to breach the outer gate, requiring a DC-20 Sleight of Hand check or the Selûnite Key found on top of the gate (#4), and then unlock the chest itself (DC-15 Sleight of Hand). Inside the chest, you will find the Helmet of Smiting.
Right next to the Locked Chest (#2), if you beat a passive DC-15 Perception check, then you’ll detect that a “stone wall” is really a secret door. Opening it will give you access to a secret room. You can also jump, fly, or use Mage Hand from the room below, where the Waypoint (W1) is located.
The secret room contains a trapped and locked chest. You’ll need to pass a DC-10 Perception check to detect the trap, a DC-15 Sleight of Hand check to disarm the trap, and then another DC-15 Sleight of Hand check to pick the lock. Inside the chest, you will find Luminous Armour.
The gate to the Selûnite Outpost can be opened easily enough, either by pulling the lever on the inside of the Outpost, lockpicking the gate (DC-20 Sleight of Hand check), or by using a Burrow Hole by the Waypoint (W1). However, if you have not destroyed the crystal atop the statue within the Outpost (#1), you will be fired upon by two statues in front of the Outpost. If the statues are disabled, you may also have to fight a minotaur here.
The key to the gate is located on top of it, on a skeleton you have to climb up a ladder to reach.
Should you exit out the Selûnite Outpost via the windows on the western side (or approach via a different way), you will soon come across a series of terrified statues on two landings, clearly the petrified victims of some creature in the area. It won’t be long before you come across the Level 5 Spectator that caused this. This tough enemy has a chance of petrifying you, as well, and can de-petrify his former pray to fight against you. You can avoid it easily by not going with your full party into the field of petrified creatures.
If you defeat the Spectator, you will be able to take his legendary Spectator Eyes in order to cast Ray of Fear. If Dhourn, whom the spectator un-petrifies to fight against you, survives, you can speak to the haughty Drow, who is actually former friends with Filro (#30), who is camped down by the Sussur Tree. He will likely attack you, however, in order to maintain his secret of the Adamantine Forge. Whether he dies during your fight with the Spectator or after, you can find the Blast Pendant, Icy Helve, and Memory Shard on his body.
If you use the Memory Shard and pass two DC-10 Arcana checks, then you’ll see a memory of the Adamantine Forge. This will trigger the quest The Adamantine Forge and mark its location on your map. The Icy Helve is one of the three components of the Mourning Frost quarterstaff. See our guide How to Get the Mourning Frost Quarterstaff for more information.
After defeating the Spectator, you can force attack any remaining petrified drow for some minor loot and 40 xp each.
A valuable Drow longsword has been wedged into a stone, making it almost impossible to pull out. I wonder why this seems familiar? Regardless, you can have this very powerful shrieking, singing sword (called “Phalar Aluve”) if you can either wrest it free from the rock with a DC-15 Strength check, or if you are able to learn the ritual required with a DC-15 Religion check (hint: it’s blood). Paladins can consider their oath with a DC-10 Religion check, and then pry the sword free with a DC-10 Charisma check.
If you perform the blood ritual to claim the sword, and if you have an Acolyte (like Shadowheart) in your party, then you’ll gain the “Last Rites of the Dark Dancer” inspiration.
7 – Bulette
Enemies
Bulette – Lv. 5
Notable Loot
Bloodguzzler Garb
At these three spots, you can encounter a Bulette, also known as a “land shark.” It’ll burrow under the ground and then erupt to attack you. When you get close to the Bulette, you’ll see a disruption in the ground, and you’ll switch to turn-based mode. The game will also auto-save, a clear warning that something bad is about to happen. The Bulette won’t do anything during its first turn, which will give you a chance to prepare for the fight to come.
Probably the most annoying attack of the Bulette is its Deadly Leap. The Bulette will jump to a location and knock Prone and back any characters it hits. So you’ll want to keep your party members separated and away from chasms. That way only one character will get knocked Prone, and nobody will get flung to their death. The Bulette can also Bite and shoot Corrosive Phlegm, but these are more standard attacks that are easier to deal with.
When the Bulette drops under 20% of its maximum health, it’ll burrow back underground, regain half of its health, and then retreat to one of the other spots where it can appear — and wait to attack you again. To prevent this, you can use a spell like Command: Halt, which will prevent the Bulette from doing anything for a turn. You can also stop attacking it when it gets to around 30 hit points, wait for it to take its turn, and then throw everything you have at it to remove that last bit of health before it can run away.
If you fail to kill the Bulette during your three encounters with it, then it’ll disappear for good. But if you manage to defeat it, then you’ll earn 150 xp, and you’ll find Bloodguzzler Garb on its corpse.
You’ll encounter multiple Minotaurs patrolling in this part of the Underdark. These giant man-oxen will not give you any chance for discussion, though, and you will have to plan on fighting them. It shouldn’t be too hard of a fight, but it will reward you with the Amulet of the Unworthy for some easy damage resistances.
You’ll discover lots of containers here, including a few locked chests. But inside these containers you’ll just find random loot — food, alchemy supplies, Thieves’ Tools, poisons, and things like that. Be careful of the traps outside the storehouse, right next to the netting that acts as an entrance. If you accidentally set off the traps and destroy the netting, then you can always jump up to the storehouse using the mushrooms and cavern walls on the eastern side.
In the back of the storehouse, you’ll find an elevator leading up to the Zhentarim Basement under Waukeen’s Rest in the Risen Road (Exit B).
You’ll find a series of mushroom platforms along the cavern wall here, leading up to a meadow above. However, as you approach the platforms, if you beat a passive DC-10 Medicine check, then you’ll notice a drow corpse that apparently fell from a great height. Relatedly, as you start jumping onto the platforms, if you beat passive DC-10 Investigation checks, then you’ll discover that some of the platforms are illusory, and if you jump onto them, then you’ll fall to the ground.
Luckily, you only need to send one character onto the platforms. When you reach the meadow at the top, you’ll find a mushroom circle teleporter there (Exit D), and when you use it, you’ll teleport to and activate the one at the bottom, which will give you a much easier way to make the trip.
The cavern wall here is an illusion. You’ll detect it if you beat a passive DC-20 Investigation check. However, detecting the illusion is not necessary. You can walk through the illusion even if you don’t know it’s there.
You’ll discover four holes here. Two of them will be empty, and one will have a Bone in it. For the fourth, If you pass a DC-15 Survival check, then you’ll realize the holes were created by carrion crawlers. If you stick your hand in the hole, and if you’re a small race, then you’ll feel a tentacle. If you pass an unspecified Wisdom check, then you’ll keep searching around and come away with a Topaz. Otherwise, you’ll be horrified, and you’ll refuse to stick your hand in the hole again. If you get the Topaz, and if you have an Outlander (like Karlach) in your party, then you’ll gain the “Nest Egg” inspiration.
Hanging from a thatch roof here, you’ll find a Gold Necklace. If someone in your party passes a DC-5 Perception check when you approach it, then they’ll point it out. The easiest way to reach the necklace is to jump down to it from above. All this being said, there isn’t anything important about the necklace. It’s just vendor trash.
Behind the spiderweb here (which you can force attack to remove), you’ll find a locked heavy chest. You’ll need to beat a DC-15 Sleight of Hand check to pick its lock, but inside you’ll find Drow Studded Leather Armour. Near the chest you might also notice the book On Educating the Faithful. If you read it, and if you have a Sage (like Gale) in your party, then you’ll gain the “Secrets of the Matron” inspiration.
16 – Executed Deep Gnomes
Notable Loot
Shortsword of First Blood
Travelling through the Underdark, you will come across a grisly scene of a pair of recently-executed Deep Gnomes — clearly failed escapees, likely from the same group that Spaw’s charge (#21) is from. You can find the Shortsword of First Blood on one of their bodies.
Whether you come here before or after interacting with the Myconid Colony (#19), you will find yourself in the midst of a group of Duergar led by Gekh Coal. They have made this beach their home and have gotten into a feud with the local Myconids, who have allowed one of the Duergar’s Deep Gnome slaves to take refuge in their colony (#21).
If you have Sovereign Glut (#25) with you, then the Duergar will become hostile immediately, but otherwise you will have a chance to talk with them if you can pass a DC-15 Religion, Intimidation, or Persuasion check, if you are a Fighter or Branded (from Priestess Gut in the Shattered Sanctum), if you detected them by beating a passive DC-20 Perception check before they spoke to you, or if you use your Illithid powers. The exception to this is if you are playing as a Deep Gnome, in which case they will assume you are an escaped slave and attack immediately.
If you talk to Gekh Coal, then you’ll discover that he is looking for the Boots of Speed that Thulla, the Deep Gnome under Spaw’s protection, stole from Sergeant Thrinn when she escaped. This will trigger the quest Find the Missing Boots. If you are able to retrieve the boots, then the Coal will allow you to sail his boat to Grymforge (Exit E), so you can deliver them to Thrinn. Of course, you’ll also be able to use the boat if you kill the Duergar.
Most interactions with the Duergar end with violence, and they are formidable opponents, making heavy use of invisibility and other transformational spells to really challenge your tactical play. On Gekh Coal’s body, you can find the unique Exterminator’s Axe.
18 – Giant Bird Nest
Between the Duergar Outpost and the Myconid Colony, there is an easy-to-miss giant bird’s nest. It is possible to jump to the nest on its northern side, but you might have to use a spell like Enhance Leap, Grant Flight, or Misty Step to make the distance. At the nest, you won’t meet any giant angry birds — luckily — but you will find a chest to loot. The chest won’t have anything interesting inside, but if you have an Outlander (like Karlach) in your party, then grabbing its contents will give you the “Clever Cuckoo” inspiration.
The mushroom-like myconids have established a permanent colony in the Underdark. There are two entrances to the colony, and you’ll get interrogated the first time you approach either one of them. Due to the Duergar at the outpost nearby (#17), the myconids are on high alert, and have to make sure your intentions with their colony won’t put them in danger. After showing you some visions, you will have to answer to them. Thankfully, the myconids are easy to convince, as simply telling them the truth, or convincing them with a DC-5 Persuasion, Intimidation, or Insight check (with a follow-up option in that case) will grant you entry.
You can also attack the myconids at the entrances, but that will turn everyone in the colony hostile, a battle that will be extremely difficult to fight your way through. If you really want to attack some mushrooms, then you should ally yourself with Sovereign Glut (#25).
20 – Blurg and Omeluum
Speaking to the shopkeeper Blurg will reveal that he is a member of the Society of Brilliance, a group of scholars who are trying to improve conditions in the Underdark. If you tell him about your parasite, then he will introduce you to his companion in the Society: Omeluum, the Mind Flayer.
This might be a somewhat disconcerting sight, given your history with Mind Flayers, but Omeluum is a bit different from most. This Mind Flayer has abandoned the expansionist and wicked goals of his kin and taken to a life of study amongst the Myconids, being a potentially very valuable ally to you in your search for answers and a cure to the parasite in your head.
If you allow Omeluum to examine you, then he’ll determine that your parasite is in a form of stasis, which is why you haven’t turned yet. This will trigger the quest Help Omeluum Investigate the Parasite. After completing the quest, Omeluum will turn into a shopkeeper, and he and Blurg will have a variety of magical hats and jewelry available for sale.
21 – Thulla
You’ll meet the poisoned deep gnome Thulla here. When you talk to her, you’ll learn that she was poisoned when she escaped her duergar captors. If you talk to the duergar (#17), then you’ll learn that they don’t care much about her, but they do care — a lot — about the boots she stole when she fled. These conversations will trigger two quests: Cure the Poisoned Gnome and Find the Missing Boots. If you cure Thulla during the former quest, then she’ll ask you to rescue the rest of her clan, which will trigger the quest Save the Grymforge Gnomes.
22 – Sovereign Spaw
Sovereign Spaw is the leader of the Myconid Colony. When you approach him, he’ll show you visions of duergar attacking his people, and he’ll ask you to “cleanse the rot.” This will trigger the quest Defeat the Duergar Intruders. Afterwards, Spaw — or perhaps Glut (#25), depending on who is in charge — will give you a second quest: Deliver Nere’s Head.
This vault will start out locked with its entrance gate hidden. Sovereign Spaw (#22) will open the gate for you when you complete the quest Defeat the Duergar Intruders. If you beat a passive DC-10 Perception check, then you’ll detect the gate. There isn’t any way to pick the gate’s lock, but you can destroy the gate by force-attacking it, or you can open it by using The Sovereign’s Key (carried by Spaw).
Inside the vault, you’ll find the camp of a dead drow elf. Luckily, the drow will have some interesting items scattered about: the book Flumph Mating Rituals, Icy Metal, and a Shadow of Menzoberranzan hood.
The book Flumph Mating Rituals is a special item. If you read it, and if you pass a DC-15 Investigation or Nature check, then you’ll detect that the text is an illusion, and that the book is really a manual for forging adamantine. The book will then transform into The Great Furnace of Grymforge, which might prove useful during the quest The Adamantine Forge.
Derryth is a shopkeeper. She’ll have a variety of items for sale, including a Caustic Ring (which adds 2 acid damage to weapon attacks) and a Corrosive Flail (which deals damage even when you miss). Derryth won’t reveal what she’s doing with the myconids in the Underdark, but she’ll ask you if you’ve seen her “dumb as a stick” husband Baelen. This will trigger the quest Find the Mushroom Picker.
25 – Sovereign Glut
When you talk to Sovereign Glut, he’ll show you visions of his circle being destroyed by the duergar in the area. Then after receiving the quest Defeat the Duergar Intruders from Sovereign Spaw (#22), Glut will ask to come with you and help you out. This will trigger the quest Avenge Glut’s Circle.
26 – A Deep Hole
This hole probably belongs to the bulette (#7). If you interact with it while you have Speak with Animals active, then a voice from below will tell you to go away — at least while the bulette is alive. After you’ve killed the bulette, you won’t hear anything from the hole.
You’ll discover a large field of bibberbangs here. If you stand too close to one, then it will expand until it explodes, dealing minor poison damage and leaving behind a cloud of noxious fumes. And since bibberbangs only have 2 hit points, if one blows up then the entire field will erupt. Worse, there is a lit Torch in the field, and noxious fumes plus fire means a huge explosion. This is notable because in the middle of the field you’ll see Baelen Bonecloak, the missing husband of Derryth in the Myconid Colony (#24). Rescuing Baelen from his predicament is the crux of the quest Find the Mushroom Picker.
If you beat a passive DC-10 Nature check when approaching the field, then you’ll remember the phrase “where bibberbang blows, noblestalk grows.” So without surprise there is also a Noblestalk (which cures all conditions and fully heals the user) in the field, but it can be a part of the quest Find the Mushroom Picker as well. Just be aware that blowing up the bibberbang field will likely destroy the Nightstalk as well as kill Baelen.
Note: If you blow up any bibberbangs, here or elsewhere, and if you have an Outlander (like Karlach) in your party, then you’ll gain the “Mushroom Enthusiast” inspiration.
28 – Sussur Tree Roots
Enemies
4x Hook Horrors – Lv. 4
Notable Loot
Sussur Blooms
The iconic Sussur Tree has many tendril-like roots extending down into the floor of the Underdark, providing a platform to climb up into the tree. But you aren’t the only one with that idea: a number of Hook Horrors have made the tree their home, requiring you to take them on if you want to pass through the area unscathed. Many anti-magic Sussur Blooms can be found in this area, too, potentially nullifying your spellcasters’ effectiveness.
29 – Sussur Tree Bark
Notable Loot
Sussur Bark
By climbing up the roots of the Sussur Tree (#28), you will be able to reach its core bark: a vital ingredient in the creation of a certain masterwork weapon that you can find the plans for and forge back in the Whispering Depths under the Blighted Village.
30 – Filro’s Campsite
Enemies
Filro the Forgotten – Lv. 5
Notable Loot
Icy Crystal
In the alcove here, mingling with the Hook Horrors who have accepted him as their own, you’ll encounter Filro the Forgotten, a Drow Wizard who has gone a little bit crazy while hiding out by the Sussur Tree. He’ll attack you on sight. If you use Speak with Dead on Filro’s corpse after killing him, or read his Scribbled Notes and Tattered Scroll, then you’ll get some clues for the quest The Adamantine Forge.
You’ll also find some spell scrolls and an Icy Crystal on Filro’s corpse. The crystal is one of the three components of the Mourning Frost quarterstaff. See our guide How to Get the Mourning Frost Quarterstaff for more information.
31 – Tombstone
“In memory of Myrna — a shining light in this dark world. May you forever gaze upon the lake you loved to play in.”
If you dig up the grave here with a Shovel, then you’ll find a Dog Collar. The interface makes it look like the collar is a junk item, but you can use it inside the Arcane Tower.
There are a number of dirt mounts to be found around the Underdark. These can be located with successful passive Survival checks, allowing you do dig the chests they are hiding up with a Shovel in order to acquire their valuable loot within.
The simplest-to-find entrance to the Underdark can be accessed by traversing the Shattered Sanctum, specifically after going through High Priestess Gut’s quarters and the stone disc puzzle beyond it, which will lead down into the Selûnite Outpost (#1).
An elevator leading down to the Underdark can be discovered in the Zhentarim Basement below Waukeen’s Rest along the Risen Road. This must be activated from the basement by unlocking the elevator (itself hidden behind an illusory wall in the Zhentarim Basement) with a key or Sleight of Hand check.
This cove is pretty well hidden. You’ll have to jump to some mushroom platforms and then interact with a cragged rock to get inside, where you can find BOOOAL and his terrifying Sickle of BOOOAL, as well as a Slippery Chain Shirt.
D – Mushroom Circle
This teleporting mushroom circle will give you an alternative to climbing the nearby cavern wall (#11), but you’ll have to activate the top circle before you can use the bottom circle.
The first time you sail this boat to Grymforge, you’ll get intercepted by Corsair Greymon and his crew. If you spoke to Gekh Coal (#17) and triggered the quest Find the Missing Boots, then you’ll be able to tell Greymon that you’re on your way to Grymforge to deliver the boots to Sergeant Thrinn, and he’ll believe you. Otherwise, to talk your way past him, you’ll have to beat a DC-15 Deception check or a DC-10 Intimidation check, or you’ll have to have been Branded in the Shattered Sanctum. Being a Drow or Duergar will make this conversation easier, while being a Gnome of any sort will make it more difficult.
If you convince Greymon that you should be on the boat, then he’ll accompany you to Grymforge, where he’ll become a shopkeeper (and sell the weapons that you’d otherwise find on his corpse). If you have a Charlatan (like Astarion) in your party, then this route will give you the “A Friend to All” inspiration when you arrive.
If you can’t talk your way past Greymon, then you’ll have to fight him and his crew. Whatever you do, don’t start the fight by attempting the DC-15 Athletics check to push Greymon into the water. Greymon is the only enemy with interesting loot, and if you push him off your boat — during dialogue — then his corpse will disappear. If you Shove him or any other enemy off a boat during the battle, then their corpse will wash up on the beach in the Underdark (near #14), and you’ll be able to loot it there.
The boat battle can be difficult. With limited space and lots of combatants, you might have good luck placing a Fireball or two at just the right spot to hit multiple enemies. Otherwise, take out the duergar one at a time, and Shove as many of them into the water as possible. When you loot the bodies, you’ll find the Bow of the Banshee, Jorgoral’s Greatsword, and the Shining Staver-of-Skulls on Greymon’s corpse, plus the Intransigent Warhammer in a chest on Greymon’s boat. Once you’re ready to move on, interacting with the rudder of your boat will allow you to continue to Grymforge or return to the Underdark.
W – Waypoints
There are four Waypoints in the Underdark, as follows:
Selûnite Outpost
Beach
Myconid Colony
Sussur Tree
Where to go Next
After you’ve explored all the crevices of the Underdark, you can go to the following places.
Arcane Tower: This tower is located in the southwestern part of the Underdark. If you can figure out how to get past its defenses and get it running again, then you’ll find some useful magical loot inside.
Grymforge: The obvious path forward, as this is the only entrance to several quests, the legendary Grymforge itself, and an elevator to Moonrise Tower.
Sunlit Wetlands/Putrid Bog: If you haven’t yet dealt with Auntie Ethel, this is a great way to get to the tunnels beneath her Teahouse (and back) immediately.
Zhentarim Basement: In order to open this path, you have to have already gone through the Zhentarim Basement, and there is unlikely to be any reason to return after being there once anyway.
Shattered Sanctum: You likely came into the Underdark this way, but in case you didn’t (and haven’t yet dealt with the Shattered Sanctum), don’t bother with this path in — you can’t get through the puzzle in the Sanctum the reverse way, so you’ll be blocked.
Graves is an avid writer, web designer, and gamer, with more ideas than he could hope to achieve in a lifetime. But, armed with a mug of coffee and an overactive imagination, he'll try. When he isn't working on a creative project, he is painting miniatures, reading cheesy sci-fi novels, or making music.
