How to Make a Dungeon in 30-Minutes or Less | DM’s Workshop

Hey hey! Happy Saturday, folks! Saturday is my Saturday campaign. I’ve already done some planning for it (in the last edition of this series) but I thought I might expand a little on the Leilon setting.

Also, I wasn’t crazy about the organization of that last article, so I thought I might clean things up a little better.

Spoilers: If you’re one of my players, you probably won’t want to read this since it contains spoilers. You’ve been warned.

How to Make a Dungeon in 30-Minutes or Less

Being a DM is hard. With life, work, and all the other distractions in the world, it can be hard to properly prepare for sessions in time. Fortunately, Fifth Edition makes it pretty easy to prepare. And if you’ve got a few useful tools at your disposal, you can build a Dungeon in 30-minutes or less.

Step 1. Pick an Adventure Type

There are two main types of adventures in Dungeons & Dragons Fifth Edition: Location-Based Adventures and Event-Based Adventures. Both types of adventures are detailed on page 72 of the Dungeons Master’s Guide.

For the example I’m using today, I’m going to pick a Location-Based Adventure again, specifically a Dungeon. The Dungeon will be under the streets of the ruined city of Leilon.

Step 2. Determine the Dungeon’s Goals

This is the part where you can turn your brain off. I’ll let you in on a little secret: I love using random tables to generate ideas. On page 73 of the Dungeon Master’s Guide, there’s a random table for the Dungeon’s Goals. I’m going to use my Dice Ex dice roller phone app to determine the result:

D20 Roll: 7 – Find information for a specific purpose.

Cool. Now I know that my adventurers will need to descend into the Dungeon for a specific purpose. But what’s that purpose?

Last time I identified a few key NPCs. One was a military officer that acted as the group’s patron. Then there was an enthusiastic commoner and a monster in disguise. Any of these could ask the PC’s to descend into the dungeon to discover what’s going on.


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Step 3. Identify Important NPCs

The last adventure set up most of the “friendly” NPCs, so I don’t want to be too redundant. It’s never a good idea to have too many characters. Not only is a pain in the ass to keep track of, but it can confuse your players, too.

Since there’s already a villain in Leilon, though, I thought I might add another one for this mini-dungeon. Again, I’ll turn to random tables, this time to the Adventure Villains table on page 74 of the DMG.

D20 Roll: 4 – Dragon bent on domination and plunder

Yo, that couldn’t be more perfect if I tried. If you read the last article, you’ll know that there are dragon cultists in Leilon. And now it turns out that there’s a dragon under Leilon? You can’t make this shit up.

Step 4. Flesh Out the Location Details

Here comes the fun part. We know the purpose of the dungeon and we know its villain. All we need to do now is to create the dungeon itself.

I have a few different sources that I like to turn to for dungeon creation. Sometimes, I’ll find a map somewhere on the internet. I’ll use either my buddy JD’s maps, Dyson Logos’ maps, or Tim Hartins–all three are professional cartographers with tons of maps to choose from.

But today I’m going to use another awesome source for maps: donjon’s random map generator. You can access it at https://donjon.bin.sh/fantasy/dungeon/

donjon
Donjon is the bomb.

I don’t want this dungeon to be too big. I want it to have around 6 encounters, enough for a single session of play. Usually, it’s a good idea to have a dungeon that’s got 1.3 to 1.5 more rooms than encounters. So for a 6 encounter map, I’ll need about 9 rooms.

Generating a map using Donjon.

I’ve put the settings to the following:

  • Name: Below Leilon
  • Dungeon Level: 1
  • Details: None
  • Map Style: Standard
  • Grid: Square
  • Dungeon Layout: Keep
  • Dungeon Size: Fine
  • Peripheral Egress?: No
  • Stairs?: Yes
  • Room Layout: Symmetric
  • Room Size: Large
  • Doors: Basic
  • Corridors: Straight
  • Remove Deadends?: All

Let’s see what it cooks up:

below-leilon-map

Pretty nifty, if I say so myself. Keep in mind that I turned off trapped, locked, and secret doors, so if I want those, I’m going to have to add those in myself.

Tip: when using donjon, you may have to play with the settings a few times to get it to look the way you want it to.

Determine Daily Encounter XP

Before I start populating the dungeon, I’m going to want to determine encounter XP. My guys are mid-way to 12th level right now and I suspect that by the time they defeat the bad guys in the town proper, they’ll probably be at 12th. Plus, they’re pretty tough. So I’m going to stock this place like it’s for a group of six 12th-level adventurers.

On page 84 of the Dungeon Master’s Guide, there’s a handy-dandy chart for knowing the amount of adjusted experience that a character can handle in a day before they need a long rest. I suspect my guys will take a long rest before descending into the dungeon, so I’m going to give them the full boat.

  • One 12th-level character can earn 11,500 adjusted experience in a day.
  • Therefore, the entire party can handle 69,000 adjusted experience in a day.

Tip: Adjusted experience is NOT the same as actual encounter experience. Adjusted experience is a virtual amount of experience used to measure challenge ratings.

Build the Encounters Starting with the Main Event

Next, I like to determine the encounters before I start sticking them in rooms. That way I keep the entire dungeon balanced. When I know there’s a villain in a dungeon, I like to start with the villain.

We know that there is a dragon that’s the main villain. But what sort of dragon?

I kind of saw the dungeon below Leilon as a burial area. So maybe I can toss a Dracolich at the party. How tough should that dracolich be?

We know from the XP Thresholds by Character Level chart on page 82 of the Dungeon Master’s Guide that a party of six 12th-level characters can handle 27,000 adjusted experience in a single encounter. Whoa, Nelly! That’s a lot. In fact, if we reference page 275 of the Dungeon Master’s Guide‘s Experience Points by Challenge Rating chart, that could be a creature of CR 20, right? Well, it could actually even be higher than that!

When you have a group of six or more adventurers, the adjusted encounter experience for a solo encounter uses a multiplier of 0.50, which means that the creature could be worth up to 54,000 adjusted encounter experience: that’s a CR 23 monster!

Keep this in mind: even though PCs can technically fight a CR 23 monster, that’s still going to be a very, very difficult encounter for them. But you know what? These guys could use a little love. Haha! But in order to soften the blow, I’ll make sure they don’t fight the thing after running through a gauntlet of bad guys.

The Villain Encounter

So what sort of dracolich are we talking about here? The theme of Leilon and the Mere of Dead Men is swamps and black dragons. So I think a black dragon is perfect. And on page 87 of the Monster’s Manual, we can see that an Ancient Black Dragon is “only” a CR 21 creature.

Of course, I’ll need to apply the dracolich template to it real quick and give it a cool draconic name. I’ll use Donjon’s Fantasy Name Generator to come up with a cool dragon name: I got Mammet.

As a dracolich, Mammet is undead and she gains immunity to poison. Plus, she can’t be charmed, frightened, paralyzed, or poisoned and she doesn’t suffer from exhaustion. Finally, she’s got magic resistance. Tough lady.

A dracolich is kind of a big deal. As a black dragon, they’re not as clever as the other dragon types (Int 16 and Wis 15), but not total dummies either.

Keith Ammann of the Monsters Know What They’re Doing describes black dragons as snarling bullies. Here’s his roleplaying notes on them:

Black dragons are cruel and brutal, and they target their weakest enemies first, so if a black dragon’s opponents have managed to inflict real damage on it, something’s gone horribly wrong, and it will skedaddle. It might accept a sufficiently attractive bargain offered by the PCs, but it will never surrender to them or agree to any limit on its independence.

What’s a dracolich doing down in the basement of a temple, though? Let’s turn to the random tables on page 90 of the Dungeon Masters Guide to get some ideas of her personality.

Since she’s a dracolich, I’m going to skip Appearance, Abilities, and Talents and go straight for her Mannerisms.

D20 Roll: 13 – Mammet fidgets.

I love it. She misses her scales (and flesh) so is constantly fidgeting when she talks. This probably makes her somewhat irritable. Next, her Interaction Traits:

D12 Roll: 7 – Mammet is honest.

What an interesting dynamic for an undead dragon. She’s honest, despite being a creature of pure chaos and evil.

Next, I need to figure out some sort of useful knowledge for her. She might know a thing or two about Tiamat, being so ancient. I originally thought about tying her into the usual BBEG, but I thought that’d be insipid. So I made this a stand-alone.

After the useful knowledge, I need an Ideal. Her ideals can be Evil, Chaotic, or Other. I’m going to pick Evil since I want a fight coming out of this.

D6 Roll: 2 – Mammet is greedy.

She’s already discovered immortality. Now she wants more. Perhaps she, herself, wants Tiamat’s powers?

What about her bonds?

D10 Roll: 5 – Mammet is captivated by a romantic interest.

Oo la la! Romance. Perhaps part of her driving force is that Tiamat killed (or enslaved) one of her past lovers.

Finally, a flaw or secret for Mammet.

D12 Roll: 3 – Mammet is arrogant.

Perfecto! That’s definitely a motivation to start a fight with a bunch of do-gooders.

Since Mammet is a villain, we also get to use the Villain tables on page 94 of the Dungeon Master’s Guide.

First, we’ll determine her scheme.

D8 Roll: 2 & D4 Roll: 1 – Mammet wants to seize a position of power or title.

She wants to be the new Tiamat.

Next, we need to know her methods.

D20 Roll: 20 & D6 Roll: 4 – Warfare via mercenaries

Mammet hopes to get the PC’s to work for her. She arrogantly proclaims that they must work for her or she’ll burn down the land and their town and that working for her is the best only option. She commands them to slay a local politician to prove their worth. Being somewhat arrogant, she doesn’t see them as a threat (they are).

Finally, we need a weakness for Mammet.

D20 Roll: 7 – The villain falls when an ancient enemy forgives its past actions.

Fascinating! This could potentially tie into how Mammet returned as a dracolich. It might even be a curse placed on her by an old foe.

In one shot, I’ve developed our villain using a little Encounter XP math, then came up with her personality and roleplaying traits. Plus, there’s plenty of hooks for future encounters should she survive the initial.

Using an Encounter Budget

Earlier, I mentioned that I’ve got 69,000 adjusted experience to work with. Well, I’ve just used up 16,500 of that (Mammet’s experience multiplied by 0.5). That leaves me with 52,500 Adjusted XP or roughly 10,500 Adjusted XP per encounter. Those are mostly going to be easy-to-medium encounters.

I think what I want to do is make it so that the temple was there to keep Mammet in check. The place is super-duper trapped so half of the encounters will be some clever (perhaps even complex?) traps designed to scare off intruders.

Mammet herself is kept in check thanks to a powerful gem that casts a white glow in the room she’s kept. The gem is one of those classic “don’t you dare take it, rogue” gems that old school dungeon designers love to toss in.

This precaution was put into place by powerful wizards since they were unable to find her phylactery (a story for another time).

The remainder of the challenges in the temple basement will be undead guardians and constructs that are there to thwart any who dare break in and maybe some constructs.

Sword Wraiths

I think a big fight with some sword wraiths (Mordenkainen’s Tome of Foes) would be pretty neat. There will be one sword wraith commander paired with five sword wraith warriors.

Referencing the encounter multipliers chart on page 82 of the Dungeon Master’s Guide (and shifting it all down one rank because there are six adventurers present), the sword wraith and its retinue are worth 11,100 adjusted experience.

That leaves me 41,400 adjusted experience.

Complex Trap

Remember that I said I wanted a complex trap, too? Those are worth XP as well! According to page 118 of Xanathar’s Guide to Everything, a Complex Trap of 11th to 17th level is worth 11,100 XP.

Speed is on the mind here so I won’t have time to invent a new complex trap. So I’ll just use the Poisoned Tempest trap described on page 120 of Xanathar’s.

Now I have 30,300 adjusted experience to work with.

Simple Trap

I think I’ll throw in a simple trap, too. This time, the trap will just have a trigger and an effect. This trap will be “dangerous”. Looking at the tables on page 116 of Xanathar’s, a dangerous 12th level trap should have save DCs of 15 (or attack bonuses of +8). The damage severity should be 55 (10d10). Or I could make it cast a 6th level spell.

I think I’ll go with the spell option. That seems pretty cool.

So I’m going to make the trap create a Circle of Death. It’ll come out of a giant skull head built into the floor with the words “Speak DEATH to Find the Key” scrawled across its brow (in another language, so the PCs really thinks they’re clever). It’s totally a trick to trip up clever dungeon-delvers. The room will have the bones of withered adventurers all around it, too. Only a wizard can disarm the trap with a successful DC 16 Arcana check to both notice and disarm it.

That trap is worth another 11,100 XP. Now we’re at 18,800 XP.

Elementals

Next up, I want a challenge that incorporates lots of different creatures. I think all four elemental types at one time would be fun. Each one is worth 1,800 XP, so combined that come out to 10,800 total adjusted XP.

That leaves me with only 8,000 more XP.

Iron Golem

Finally, a good ol’ fashion construct could be fun. Iron golems are worth 15,000 XP, but since there’s six in the party, it’ll only be worth 7,500 adjusted XP. Boom. Nailed it.

Placing the Encounters

Now it’s just a matter of putting each of the encounters in appropriate locations. Here is what I’ve determined:

  1. The elementals will take up Area #1. They’re all large and should have lots of room to move. I want the ceilings to be high in this place so there’s plenty of room for the air elemental to get around. Plus, the floors should be made of unworked earth and stone so the earth elemental can use its burrow to its advantage. There will be a system of pipes (or even miniature aqueducts) that the water elemental can move through, using its swim speed and water form to its advantage. And finally, the fire elemental will work with the earth elemental on the ground. Perhaps they could even combine as one? The door leading to area #2 will be sealed shut (I’ll make it damn near impossible to open). It will require the PCs to locate three keys scattered throughout the dungeon (there are three wizard heads in each of the doors).
  2. Mammet’s tomb is in Area #2. The center of the room has a massive black glass sarcophagus where Mammet is trapped. There is a jewel fixed into the ceiling creating a bright light throughout the room. The walls are made up of bas-reliefs of the ancient wizards that trapped her there. Removing the gem wakens her (and also deals, like 4d6 radiant damage to anyone that touches it just for the hell of it). All of the doors leading into Mammet’s chamber require the three keys to enter. I’ll take out the northern and southern doors so there’s only one way in.
  3. The Circle of Death trap is in Area #3. To enter area #8, the PC’s will have to trigger the CoD trap.
  4. Area #4 holds one of the three keys.
  5. Area #5 is the iron golem which blocks the way into the hallway. It has one of the keys around its neck. If I really wanted to be an asshole DM, I could make the room full of fire traps that shot fire out at the PCs at random intervals (they’d do 3 attacks rolls at initiative count 30, targeting random locations of the room). This would not only hurt the PCs, but heal the iron golem, too. Totally going to do that.
  6. Area #6 is where the sword wraiths are. The room is full of columns, allowing the sword wraiths to duck and cover with their longbows. I might even make the room they’re in have a balcony (the stairs off to the side lead up to it). This makes for a much more interesting encounter.
  7. Area #7 is the tempest trap. The weird “closet hall” is the mechanism the controls the Tempest trap.
  8. Area #8 is where the final key is held.

And that’s it! The dungeon is fleshed out. I know it may look like a lot of work, but this type of stuff I can crank out in about 15 minutes thanks to random designs and a quick scan of monster books.

Tip: old school D&D isn’t about stuff always “making sense” together. It’s just rule of cool, baby. Gary Gygax named monsters after plastic toys with the first things that popped into his head. Rust monster. Bullette (it looks like a bullet). Owlbear. Just have fun with it.

Step 5. Find the Ideal Introduction

Back to the random tables on page 74 of the Dungeon Master’s Guide, I don’t really need to roll for an adventure introduction since I’ve already got one. So I can skip this. Otherwise, I’d roll to see how the PC’s learn about the adventure.

Step 6. Adventure Climax

All that’s left to do is to plan out the final climax. Again, I’ll roll on the random table on page 75 of the Dungeon Master’s Guide:

D12 Roll: 1 – The adventurers confront the main villain and a group of minions in a bloody battle to the finish.

Well, I more or less already planned this (admittedly, I took the steps a little out of order. But I know that my PCs will be fighting Mammet in the end. After 1,000 years of slumber, she’s cranky and wants to pick a fight. Knowing that her phylactery will keep her safe and the gem holding her back has been destroyed, she understands that if she wins the battle it’s a win for her and even if she loses, her soul can find a new dragon corpse which will make it much easier for her to escape this prison than flying away. Win-win situation!

Step 7. Plan Encounters

I kinda already jumped the gun on planning encounters, but one thing I did forget was stocking treasure. Just like last time, we’ll do this the easy way and use random tables.

Page 135 of Xanathar’s Guide to Everything has a distribution of Treasure Hoards by tier. At 11 – 16, I get twelve rolls on the Challenge 11 – 16 table. I’ve already used two for this tier, but there’s an average of two per level. The PCs aren’t going to hit level 13 with the experience gained from this dungeon, so they’re probably good for at least one hoard of treasure.

On page 138 of the Dungeon Master’s Guide, I can roll up some random treasure for this adventure. I don’t see the place being “gold” heavy, but it’ll at least give me some values for other stuff I can throw in there.

I rolled 11 on the GP table and 23 on the PP table. That’s a total of 11,000 GP and 2,300 PP. This might seem like a lot, but don’t worry. This is totally in line with what PCs are capable of earning at level 12.

Next, I’ll roll up some gems, art, and magic items.

D100 Roll: 75 – three 250gp art objects plus a +1 weapon and dragon slayer.

I swear these dice love me today. If you aren’t familiar with dragon slayer, it’s a +1 sword that lets you deal an extra 3d6 of the weapon’s type.

I think it’s appropriate to give dragon slayer to the sword wraith commander. The other +1 weapon will be his longbow. This makes this group the original people who kidnapped Mammet and put her in place. However, they took considerable damage from the fight. They’ll have acid scars all over their face and their armor will show the old burns.

Each of the keys will be jeweled and worth the 250 gp.

Finally, the big gem will be worth the total value of the gold and platinum I rolled up, so 34,000 gp. The thing is as big as a pumpkin.

Easy peasy.

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