Deep in the pits of most worlds in Dungeons & Dragons is the Underdark, a vast world of tunnels, caverns and more where Mindflayers, Beholders and all sorts of other monstrosities reside. However, it is also the seat of civilisation, with the elven subrace of Drow making a home there. The Underdark is a place which can be terrifying to travel through, both as a player and especially as a Dungeon Master.
Unfortunately, due to how rare it is sometimes to get to the Underdark, it may be hard as a DM to come up with the right encounters to throw at your players during their deep journey. Thankfully we've got you covered with some weird and wild events for your adventuring party to come across.
10 Mind Flaying With Us?
Mindflayers are a terrifyingly common thing to find lurking among the Underdark. Though they are normally hostile creatures that seek to suck your brains out, it may be fun to push the party when they come across a group of Mindflayer children playing a game. The children apparently have no knowledge about devouring brains and have no interest in it.
However, whether these are truthfully Mindflayer children who are playing a ball game and would like to invite the party to play, or are actually Mindflayers disguised as child versions of themselves to lure others in, is up to you. Though it may be a bit more fun to play around with the former and see how your party react to this terrifying foe actually being gentle for once.
9 What Are Ya Buying?
Merchants can either be a blessing or a bane to an adventuring party, but what about a mystery? If you have a magical merchant NPC you've always wanted to use, then now's the time to have them be "The Shady Merchant" who somehow shows up in the Underdark. An odd place for a merchant to be, for sure, but even odder is to have the character be vague with their responses to any of the player's questions such as how they're in the Underdark.
Having a merchant here not only opens up a mystery but can be a great resource if the adventure becomes too dangerous and the party desperately needs some better magic items or healing potions to help them out.
8 The Lost Priest
The Drow have a very interesting society with most of them dedicated to the goddess Lolth. However, what happens when the party stumbles upon a priest who seems to be lost in the Underdark? Though he may appear desperate and in need of help, their loyalty to Lolth can spark an interesting discussion between the party, especially if any of your players are followers of other deities.
Though the followers of Lolth are seen to be conniving and dangerous, having one at your party's mercy can make things appear more grey and allow the party to learn a little more about Lolth and any Drow civilisations nearby.
7 A Drowning Drow
Less of a moral quandary and more of a problem, the party stumbles onto some sort of lake in a cavern and sees nothing odd until a Drow breaks the surface and call to the party for help.
It may seem simple enough, an innocent person drowning and needing help. But it's not that the Drow can't swim, as they warn that "it" has them before they are dragged beneath the surface once more.
As to what "it" is lurking in the lake, the party don't know, but they only have moments to decide whether they want to swim to the lake and rescue the Drow or to not risk encountering the monster within. There are plenty of terrifying aquatic foes for you to pick, from aboleths to marids.
6 Statues Of Lost Deities
The Underdark is a terrifying place, and what could be more terrifying than unanswered questions? Two headless statues made of stone sit, defaced and damaged, perhaps by people or perhaps just by time. However, there are markings in Celestial that refer to two deities that have never been heard of. Who are these statues? Who made them?
All of these are questions that could be figured out through some Investigation and History checks. However, your party won't be able to find everything on these lost gods, and it can further add some creepiness to the already spooky Underdark, setting a very tense atmosphere.
5 An Elder Brain Walks Into Therapy
Life gets all of us down sometimes, so what happens when something similar happens to an Elder Brain? Another nice spin on the classic "bad monster turned good", players come across the terrifying Elder Brain, except it's not connected to anybody or anything.
For some reason, it just can't seem motivated to do the evil schemes that typical Elder Brains like to do and on top of that, being unable to connect with others has left it lonely, which has only made the situation worse. Now that it has someone to talk to, will the players be able to cheer it up and realise there's more to life than running a hivemind?
4 The Unluckiest Ship (Not) In The Sea
Every sailor is likely to get caught in a storm or two, but there has to be a level of unlucky that is a ship being sucked into a magical storm that teleported it into the Underdark. At least, if any of the crew are alive, that's what they'll tell you. Whether abandoned or with some survivors, this unlucky vessel can be found by the party to either be something to loot or to help any trapped survivors.
The image of a ship being stuck in the Underdark is a haunting one which will entice players to check how and why a ship ended up here in the first place. If you want to go further, you can even come up with what sort of magical storm occurred, perhaps for a future storyline.
3 Sick Colony
We've already met with Mindflayers once, but what happens when players come across an entire colony of them that are peaceful? In this situation, the players find a small village of Mindflayers, living in huts, with daily routines and such. But the Illithids are plagued by an illness, and the party may just have the cure.
Since they've stopped devouring brains, they have been falling ill. However, an alchemist has come up with the perfect solution to use humanoid blood to form a cure. The local Drow may have refused, and so it could be up to the party whether they trust the Mindflayers enough to give some blood and help their sick, or to leave them to their fate.
2 Lone Survivor
If there are anything players will come to understand, it's that surviving in the Underdark is no easy feat. But that could only raise more questions when, despite struggling as a group of people, they find a lone survivor. The survivor is from an adventuring party who all died when their camp got attacked, leaving them all alone.
They have managed to survive for days by sneaking around, catching very little sleep and from the rations they have left, but their supplies are running dry. However, if they decide to help the survivor, they will come to find out more about them, their adventuring party, and the dark truth about how they survived the attack. Did they abandoned their party during the battle? Maybe they were responsible for the attack in the first place?
1 Witch Way Adventuring Party?
It seems for such a dark and mysterious place, the Underdark would also host magic of a similar nature. That seemingly is the case with this encounter, when the party hear the sounds of battle, and come across two witches fighting it out with a circle of runes between them.
When they spot the party, the first witch will explain that they were meant to use a teleportation circle, but the second witch manipulated the runes into a dark ritual which will absorb the other person's magic.
The second witch will claim that they were the one trying to form a teleportation circle and the first witch is the one who manipulated the runes. Only one of them is telling the truth, and with little time due to the battle, this is one way to keep the party on their toes as they have to make a decision and just hope it's the right one, or else they could soon find themselves fighting a nefarious witch as well.