D&D 5E Help me grok mega-dungeons

My last campaign involved a mega-dungeon, depending on how you define "mega," I suppose. It had 11 levels with about 15-20 areas per level. Different factions controlled various levels. It culminated in a final showdown on another plane with a shadow dragon. (I wanted this campaign to involve a dungeon and a dragon.)

The basic premise was that the dungeon was the manifestation of the dragon's power while it was trapped in another realm known as The Shade. Once a week or so, the dungeon (called "The Delve" by the locals) would appear in a cursed forest known as The Duskwood for about 24 hours. Signs and portents in the nearby town of Grimdark would point to its arrival at which point adventurers could plumb its depths. I put a timer on it: In 20 weeks, the Shadow Wyrm would escape and wreak havoc upon the land. In the meantime, the presence of the dungeon had corrupted the forest, once home to the reclusive fey.

I set it up as a town-to-dungeon D&D experience with consistent phases of play: Warm-Up Phase, Town Phase, Travel Phase, and Delve Phase. There was also a Short Rest/Camp Phase when the PCs rested. Rests were reconfigured to 8 hours for a short rest and a week for a long rest. Since the Delve only appeared for somewhere around 24 hours at a time, the players had to manage their travel time and number of rests they took per expedition. There was a hard-stop in real time around 4 hours into the session at which point the Thrice-Damned Horn would sound. If the PCs didn't beat feet out of the dungeon at that point, they risked being trapped when the Delve re-entered the Shade. (This meant your character was driven insane and became an NPC.)

To me, it was enjoyable because of the number of meaningful decisions that were built into the structure of the game. The players could figure stuff out and strategize to achieve the goals they themselves set week to week. As DM, it was easy to run because of the consistent structure and the set adventure location. This meant prep was a little heavier, but it was fun to put together.

@Lanliss and @Valmarius both played in this game, so they may have some other thoughts.

This is a pretty cool campaign idea, thanks for sharing it.

I need to add more time elements to my own games... doors that open for only short periods of time, or shrines that grant a boon only on a night of the new moon. If you manage campaign time carefully enough, there is a world of opportunity here.

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First Post
@Lanliss and @Valmarius both played in this game, so they may have some other thoughts.

I think the best thing about this campaign was the structure. We spent 95% of our play time exploring, fighting and parleying in the actual dungeon and there were always clear risks and rewards. A PCs passive perception could be used to watch for danger, search for traps, or locate secret doors and the fact that we were always in the dungeon meant that there was a possibility for any of those at all times.

One of the other cool things about returning to the same dungeon time and again is the familiarity you build with the place. Venturing through areas you beat when you were lvl 1 or remembering to 'ride the snake' in order to get past the traps on level 6 or hitting a random encounter in that spot your comrade died two weeks ago, all add to the character of the place.

Flexor the Mighty!

18/100 Strength!
I don't know if I can help you understand them anymore than anyone else but for me a megadungon is great, a huge area with tons of combat, exploration, puzzles and treasure that the players can focus on. They can come and go usually. They can get whipped, flee, re-plan, and hit it again. Now a lot of that goes for any encounter situation but for my group we don't want story heavy and the dungeon provides the perfect area for adventure gaming. Sure if you like to write out a long detailed history for your PC and want to have your PC talk a lot and wear puffy shirts it may not be for you. If you think dying to a random rot grub is a bad thing then the classic mega dungeon with random encounters out the wazoo and illogical traps isn't your deal. Which is cool. I like game environments that stimulate and challenge the players to outwit the dungeon design rather than stretch their storytelling legs. Storytelling is what you do after the sessions when talking about what happened.

This probably didn't help.


I really didn't enjoy the PotA megadungeon, but it may have been an issue with how it was run. I found it to seem endless and pointless. A Megadungeon with clear and interesting boundaries between levels would be more interesting.

Agreed, unfortunately the 5e DMG advises against this, arguing that the traditional dungeon model (clear boundaries between levels, monsters get more difficult the deeper you descend) is likely to feel like a "grind"


DungeonEditionSizeWhat I've heard/read
Anomalous Subsurface EnvironmentOSRMegaGonzo paranoia/scifi inspired “dungeon.”
BarrowmazeOSRBigLots of undead.
Castle Blackmoor0e/3e?Mega?Dave Arneson's dungeon.
Castle Greyhawk/Castle Zagyg0e/C&CMegaGygax's personal dungeon, which was never actually released. Castle Zagyg was to be a published form, but only 1st level was published.
Castle of the Mad ArchmageOSRMegaReplacement for Castle Zagyg. 1st level was fairly funhouse.
Castle TriskelionOSRMegahttp://castletriskelion.blogspot.com/
Castle Whiterock3.5CampaignI think this is pretty good.
Caverns of Thracia0e/3.5BigGold standard for interesting maps and connections between levels.
Dark Tower1e, 3.5BigGonzo, open level plan
Darkness BeneathOSR?Appeared in Fight On. Levels contributed by multiple authors.
Depths of Felk Moor5eMega?Levels 1-10
DevilmountOSR?A send up of Dwimmermount
Dragon Mountain2eBigFor high level, but lots of kobolds
Dragon's Delve3.5e/PFCampaignMonte Cook's dungeonaday.com, apparently no longer available
DwimmermountOSRCampaignFrom author of Grognardia, completed by Autarch.
Dyson's Delve DeluxeOSRCampaign?Levels 1-6
Emerald SpirePFCampaignLevels seemd fairly small, levels contributed by multiple authors
Eyes of the Stone Thief13A?A living dungeon
Grande Temple of JingPFMegaTemple created by trickster god, levels contributed by multiple authors
Greyhawk Ruins2eMegaThis is WGR1 (not WG7 which is the joke dungeon). Probably not particularly related to Gygax's actual dungeon.
KhosuraOSRBigAppeared in Fight On. 4 levels I think?
Lost City of Barakus3eBig/CampaignAbout 5-6 levels I think, plus wilderness and urban encounters in the module.
Maure Castle1e, 3.5?Rob Kuntz's dungeon. Three levels appear in WG5, more levels appeared in Dungeon Magazine. I don't think the full dungeon was actually published.
Maze of the Blue MedusaAgnosticBigWeird fantasy?
Mines of Khunmar1e?MegaWas maps and rough notes. Not online anymore as far as I can tell.
Operation UnfathomableOSR?Kickstarted, not sure if it is available yet.
Ptolus3.5?Mostly a city guidebook, only short description of the dungeons
Rappan Athuk3.5, OSRMegaThere's a reason Orcus is the mascot of Necromancer games. I thought this was an inspired old school dungeon.
Ruins of Myth Dranor2e?Ruins of an elven city. Does it have dungeons below?
Ruins of the Dragon Lord3eCampaignI know nothing about this one
Tegal Manor0e/1eBig?Does it have dungeon levels?
Temple of Elemental Evil1eBigCompeting elemental sects
Undermountain2eMegaA true megadungeon, but sparsely described.
World's Largest Dungeon3eMega?Start the adventure trapped in the dungeon

Monte Cook's The Banewarrens. It's not a mega dungeon, but it's a very large dungeon. It is not perfect, but it's one of my very favorite dungeons. First, it's got a great high concept--an ancient vault for evil artifacts. Second, it's a clever combination of dungeon crawl and urban adventure. What happens in the dungeon impacts what happens in the city, and vice versa. Dungeon/urban adventures are probably my favorite genre, due in large part to The Banewarrens.

Also, I'm a big fan of Eyes of the Stone Thief. It's another great high concept and the execution is more or less perfect. It, too, is a clever combination of dungeon delving and adventuring in the wider world. I have not run it, but when I do I plan to turn it into an entire campaign running from 1st level to 10th or higher.

In both cases, the dungeons very much define the entire campaign, even if players do not spend all their time in the dungeon.


Victoria Rules

Nice chart. :) May I lob in a few tweaks and notes?

Tegal Manor - the manor building is the "dungeon". And quite big, but not mega. I'd check further, but I don't have a complete version (various bits are missing). It's also really expensive these days.

I'd upgrade Temple of Elemental Evil (the original) from 'big' to 'mega': not as many levels as Rappan Athuk but some of them are massive. Can't speak to the later 'return to' version.

Ruins of Myth Drannor - the city itself is the "dungeon". I'd list it as 'campaign'. There's not much below it; the dungeon-crawling consists of going through the various buildings. There's some bits that tie it all together, however, and several suggested plots or storylines included if you don't just want to run it as its own little sandbox. Another way to think of it - and of perhaps some others you've listed as 'campaign' - might be 'mini-setting'.

Given that, B-10 Night's Dark Terror is also a mini-setting within a single module - lots of little adventures (some connected, some not) but no single big or mega piece to it.

City State of the Invincible Overlord (written for 0e) nicely fits the "Mostly a city guidebook, only short description of the dungeons" way you describe Ptolus.



Ruins of Myth Drannor - the city itself is the "dungeon". I'd list it as 'campaign'. There's not much below it; the dungeon-crawling consists of going through the various buildings. There's some bits that tie it all together, however, and several suggested plots or storylines included if you don't just want to run it as its own little sandbox. Another way to think of it - and of perhaps some others you've listed as 'campaign' - might be 'mini-setting'.

Slumbering Tsar is a huge dungeon-city with some wilderness parts, so might fit in here as well.

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