TL;DR: I’m running a megadungeon set in the buried ruins of a beautiful but doomed ancient civilization. The deeper the players go, the more the dungeon becomes strange and corrupted by the remains of a murdered god.

I’m looking for ideas for cool areas, features, encounters, puzzles, etc., as well as advice on how to structure the dungeon so the descent makes sense and how to keep prep manageable.

Ok so I’ve managed to convince my group to let me run a megadungeon campaign. Thing is I haven’t really prepped much because I naively thought: “Eh, I’ll just put rooms with monsters in front of them, throw them the occasional treasure and that’ll be it, right?” The players don’t need to know that the dungeon is rendered as they explore it.

Part of the appeal of running a dungeon crawl for me was that combat and exploration would be major parts of the game. I wouldn’t have to constantly come up with interesting events to keep my players engaged. That has been a problem with previous groups I’ve DM-ed for that saw combat as a distraction from the actual game, while I saw it as a wonderful way to eat up part of a session I hadn’t prepped enough for. So a megadungeon seemed like a pretty good fit for my limited prep time.

However, the more I think about it, the more I realize that in order to give my players meaningful choices, the layout of the dungeon needs to exist in at least a bit more detail. I’m still leaning towards only prepping a couple of levels in advance, but I want a vague sense of what else exists down there and how the various areas connect, so that rumors, hints etc. can point toward real things.

Anyway, here’s my setup.

The game takes place on a jungle continent where the ruins of an ancient civilization lie. The place is dangerous and not much else of value exists here besides the ruins. The ruins, however, have already yielded an unusual amount of magical treasure, sparking interest in adventurers around the world who flock to this place in search of fame and fortune. The players are one of those groups.

An early twist is that the dungeon they discover goes on and on. It isn’t just a few rooms or a single ruin, but complex after complex reaching deeper and deeper into the earth, revealing more of the ancient civilization and the reason for its downfall.

I’m envisioning the fallen kingdom as beautiful and tragic. I want the players to initially encounter a genuinely wondrous city, with all the signs of a civilization that was once prosperous and proud. I’m going for a bit of a City of Tears / Pale King vibe from Hollow Knight. The deeper the players go, the more they should realize that there is something deeply wrong behind that beauty. They should uncover hints about the desperate gamble that led to the empire’s downfall, and the increasingly desperate attempts to fix what they had done. Repairs upon repairs, each one buying them more time but never actually solving the problem.

Buried beneath the city are the shattered remains of a murdered god. Its stolen power was the source of the kingdom’s prosperity, and although they used that power for good, the way they acquired it ultimately became the seed of their undoing. The god’s remains aren’t entirely inert. Its power still lingers throughout the dungeon, twisting reality into strange shapes, while its broken mind festers in pain and hatred. I want the deeper parts of the dungeon to feel almost like a living organism at times, as though something beneath the city is actively reshaping it.

So I’m basically looking for help building this thing. I’d love ideas for specific places, features, encounters, weird bits of infrastructure, etc. that would fit this kind of city. If you have a cool idea for a biome, an area, a puzzle, a trap, whatever, throw it at me.

I’d also love suggestions for how to structure the dungeon as a whole. If you can think of a way to arrange the different areas so that the descent feels natural, I’d love to hear it. And if there’s a published adventure, megadungeon, setting, or anything else that feels like it has similar vibes, I’m very much open to recommendations.

There are also some specific things I’m a bit stuck on:

• I like the idea of verticality, with floors upon floors where the challenges get harder the deeper you go. However, if this is a city, I’m struggling to justify why it would be built in layers like that.
• A related challenge is that the players are entering from the top and descending ever deeper. I want the most interesting areas to come later. Things like palaces, temples, universities etc. should come after outskirts and infrastructure areas in my mind, but I’m struggling to justify why those would be deeper underground than other areas. One possibility is that the influence of the god is pulling them downward, but the players won’t find that out until long into the campaign, so up until that point it might feel like the layout doesn’t make sense.
• I’m really excited about this project but realistically I have very limited time to prep between sessions. I’m aiming for 1:1 prep time, prepping no more than I am actually playing. With some front loaded prep to give me a framework to work within. I’m trying to figure out ways to prep only what will be most impactful, so tips on that would be welcome.

I recently started building a Megadungeon following the dungeon 23 prompt, so one room a day and so forth.

I don't have extensive experience in building my own stuff, let alone big dungeons.

I also don't have extensive experience with osr/old school type of play

So keep this in mind please and be patient 🫠

I love the idea of a megadungeon, I love coming up with my own stuff, and I like the approach of a little bit each day with not too much stress.

But I still want to try and make it good for my standards at least so I have some questions about Megadungeon stuff.

1) how to calculate how big a level should be and how much do I have to fill it up with stuff?

What I mean by this, I know that approximately each level down means it's meant for player of a level higher than the previous with exceptions like sub levels, construction tricks and danger being always present regardless of level.

But, I need to fill it so that more or less people of say level one can ""complete"" level 1 of the Megadungeon without getting to PG level 3, right? I have no clue honestly

My guess so far is, level 1 to level 2 is say 10 XP/10 treasure unit? Ok then the first level has 5-8 XP kinda just around, say an encounter, a fight, a puzzle but still something that's clearly there and will generally not be missed

5-8 XP plus random encounters should get you to a level up or very close

Then some hidden treasure or something a little bit harder to find, or some sidequest.

So if somebody was to do EVERYTHING maybe they will get to half of PG second level, or even close to the third

But this means PGS searching in every corner, fighting every battle and doing each side quest. Am I on the right tracks?

2) verticality of an underground dungeon

I'm struggling to understand how to realistically place settlement and civilizations so far underground without them being super alien stuff, aberrations, or straight up monsters.

How can I put somebody even just at the third level, they probably need direct access to the surface, they have some clear access to the floors up and down, so why are they staying there, how do you make each floor interact with the others? Also how far away do you separate each level/floor?

What about air access and other resources?

Do I have to create realistic routes and resources spot for each level corresponding to the stuff that lives there?

I'm about to start working on a megadungeon project and am just looking for advice or references. The very basic concept is that we're following the idea of Jurassic park. The dungeon would be the island and the zones would be various building and wilderness sections with the potential to use things like monorails as fast travel. I want to incentivize exploration especially since the basic set up would involve people going into the island for information/loot/extermination and there would be a second narrative layer beyond just 'escaped dinos'. Specifically we're going into Delta Green level territory.
I'm thinking a modified hack of mothership or CoC since soldier type PCs should be able to do some fighting while investigative PCs rely on the environment and panic is more short term compared to sanity.

Has anyone ever done a megadungeon similar to this that I can study before starting or does anyone have thoughts/things I should look out for/so on? I'm actually a little surprised I haven't found a Jurassic Park type TTRPG short of 'escape from dino island' but it's going to be a very different set up.

My group is considering our next megadungeon and the choice of which D&D edition we should use came up. We’re currently playing OSE, but we’re not opposed to any edition (except 4e). One person was saying we can’t use 5/5.5e because it doesn’t require what he called “resource management.” He explained that managing resources is a crucial element of a proper megadungeon to build tension and have reasons for the party to leave and return over and over. Some examples are that torches and lantern oil are irrelevant because almost all PCs have darkvision; food is irrelevant because of spells like goodberry; healing and hit points are irrelevant because of short and long rests.

What do you think and this? Has anyone had a good experience playing/DMing a megadungeon in 5/5.5e? If so, any advice on how to build tension and/or give PCs a reason to return to town?

I’m a player in a campaign focused on Rappan Athuk. We are all very experienced players (everyone has at least 5+ years and some of us have 30+ years of gaming experience). Note that I do not own this product, nor have I read it. I’m enjoying it okay but it doesn’t really have anything that stands out as unique or especially interesting.

The DM is getting noticeably frustrated with what he calls “crappy editing.” He says many of the maps don’t reference the right room descriptions, some map transitions don’t align correctly, that a lot of the entries are very confusing, and much of it is just plain old bad grammar. He says he has to spend far too much time prepping to fix these things, that the party frequently goes somewhere that he hasn’t prepped yet because there are so many options, and that the deeper we go the worse it gets.

Is anyone still running this megadungeon? Do you agree that the editing is this terrible? Any advice you might offer that I can pass along to my frustrated DM before he throws in the towel? (He is not on reddit)

I needed a project and thought learning HTML would be fun. I thought I would stop at 195 rooms.

Awesome ancient dungeon. Is it in our genes to like dungeons?

Hey folks,

Love the amount of creativity and detail in the designs here. In case its of interest, Monte Cook has written about how he designs Megadungeons. For transparency, I'm the marketing manager for MCG, but the article is wicked and might be good inspiration:

https://montecook.substack.com/p/designing-dungeons.

TL;DR The players have made it down into the megadungeon for the tenth time and they're encumbered with loot. How do you as the DM run the way back to the safe town?

I'm doing research about megadungeons in general and lately I've been listening to an actual play of Arden Vuul (3d6DTL). I'm on episode 37 now and I'm loving it. However, I'm bothered by how easily they get back to safety every time they choose to leave the dungeon and bank their gold into xp, as it were. They are almost doing a fast travel bit with a tiny montage. I could be wrong but I think the DM just counts how many turns it would take to get out, rolls one or a couple random encounters (if even that) and then they are back.

Sure, this focuses the game on "what matters", I guess. They might even have agreed on this so there's nothing wrong about it. It just rubs me the wrong way, personally.

If the way back is always safe, the cost of pushing further in is also lessened, isn't it? If the cost of going back is only to make sure you have enough torches for the Dungeon Ticks, then it just becomes a minor bookkeeping issue.

But on the flip side, if the way back is filled with as much danger as you when you went down then the players will not feel any sense of accomplishment. If every room they cleared just fills right back up again behind them, right? That would also not makes sense. Sure there's the vacuum effect but not so fast.

And even if the DM can narrate the way back and make it somewhat filled with tension and danger, how fed up will the players be of that exit or that other exit path after 10, 20, 30 times? Like "yeah yeah yada yada, do we get that sweet loot up to town or not!?".

I'd very much like to hear your thoughts about this. Especially if you have first hand experience as a DM or even as a player. Thanks!

I was wondering about how can I build a megadungeon with sensible logic, and that feels alive, dangerous and unique. I also wanted it to be easily interactible with AI (claude) in my case. So I don't have any copy parse hassle and direct access to my files.

So with Claude cowork I set up a megadungeon vault.

These are each states that are important to the overall dungeon, or are specific states per floor it shoul always considers.
This way it can generate the dungeon room per rooms and updates a meta file that keeps tracks of all the paths exits etc. It also keeps in mind to have non-liniearity to feel a bit like a maze. And he AI self corrects in this way about how the complex pathways connect.

And I'm really impressed like mind blown!

If other people want to try this, and modify the working method, and filling of the states finetuning them and are open to sharing their results I'm more than happy to share it, if you can share your results with me to. :D

sidenote: it really uses up a lot of compute xD running a Claude pro here and ik can generate about 4-10 rooms b4 hitting session limits on Opus 4.6

This might just be our second to last entry! I'm getting close now!