D&D 5E – Old School and Megadungeons

Recently, I’ve been talking about using D&D 5E for an “old school” campaign style.


A key part of the early years of this hobby was the dungeon (it’s right in the name of the game). The very first D&D campaigns involved an individual creating a dungeon, and the players creating characters to explore it. In fact, dungeons were there long before hexcrawls became a thing.

Many of these dungeons were fairly large, facilitating long-term play. Players were expected to have their characters make multiple forays into these dungeons, exploring one section at a time and recovering what treasure they could, with retreats back to the local settlement for rest and recuperation in between the delves.

Dungeons could be of pretty much any size. Some were fairly small, designed to be explored and completed in a single playing session. Others had a few levels to them, providing a few weeks of play. Larger dungeons might be large enough to provide enough adventuring opportunity for the characters to gain multiple experience levels through the exploration (e.g. The Temple of Elemental Evil).

And then there were the megadungeons—dungeons that provided enough material to be the main focus of an entire campaign.

The History of Megadungeons

While megadungeons were definitely a thing among players of D&D in the early years, published examples are rare. Gary Gygax’s original dungeon under Greyhawk Castle was never fully published (and don’t even mention the 2E adventure Castle Greyhawk adventure put out by TSR after Gary was ousted).

So it wasn’t until the release of 2E that megadungeons really started getting published with any regularity. Aside from the terrible Castle Greyhawk, there was the revisited and much better Greyhawk Ruins, the Ruins of Undermountain boxed set (followed up a second boxed set and some additional sourcebooks and adventures, and the Night Below boxed set.

More recently, with the rise of the Old School Renaissance (OSR) movement, the development—and publishing—of newly-designed megadungeons has become a focus for some people within the RPG publishing industry. These include (but are not limited to):

In my own games, I’ve recently used Goodman Games’ Castle Whiterock for part of my current AD&D 2E campaign that I run for some friends. It was written for D&D 3.5, and I’ve converted it as the players have explored the various levels. It has some good ideas in it, but the editing is absolutely terrible, and there are far too many inconsistencies between the maps and the room descriptions. I’m very glad I picked up the PDF on sale for about $5 (since its current price is $59.99). After exploring a few levels, I’ve given up on it and started to use other resources for the lower levels (like the great Gates of Firestorm Peak). While the overall hook of Castle Whiterock is decent, it requires far too much work—in addition to the conversion to 2E—to make it playable.

A Campaign Dungeon

Spending most of a campaign in a single dungeon complex requires a particular style of play that is not for everyone. And it requires the dungeon to be interesting enough, and provide enough different types of challenges and interactions, that the players don’t just get bored.

The key to designing a campaign dungeon is that it needs to be more than a bunch of rooms and corridors with different monsters scattered around on each level, increasing in danger as you go deeper. You can do that, of course, but after a while it gets very stale.

A well-designed megadungeon is a setting unto itself. Some key elements of a good megadungeon are:

  • multiple regions, each with a different tone/feel
  • different factions
  • opportunities for exploration
  • opportunities for roleplaying interactions
  • multiple possible routes to and through various areas (including back the surface)
  • a good reason for the various monster/NPCs groups to coexist in the same megadungeon (even if some are at war with each other and others have a “leave them alone” stance)
  • a decent scattering of mysteries, puzzles, tricks, clever traps and other non-creature obstacles or interesting features
  • a fairly easy way for PCs to discover information about the megadungeon (key parts of its history, or the reason certain elements are the way they are) so that all of the background doesn’t only get seen by the DM

How About 5E Megadungeons?

At the time I write this, the only megadungeon I could find specifically for 5E that was available for purchase was Barrowmaze (and I noted the problems with the 5E conversion above). But does the lack of published products indicate that it is impossible to run a 5E campaign with a megadungeon?

No, but it does require some tweaking.

As I’ve been focusing on old-school play in this series of posts, I would continue this approach with a megadungeon. Specifically, my post on XP and Treasure outlines some of the issues with the current XP system and how it interacts with old school play. So I would recommend adjusting the XP awards as noted in that post when using a single enormous dungeon as the main focus of the campaign.

But the biggest challenge, of course, is that the lack of published megadungeons means you will have to do most of the work yourself. Personally, I think that’s one of the fun elements of being a DM, but of course YMMV. For those who love to tinker with the game when you’re not at the table playing, however, designing a megadungeon can be an amazingly enjoyable experience.

And with your own creation, you have the opportunity to tinker with the lower levels while the PCs are still exploring the ones above, adding new ideas, riffing off ideas the players discuss at the table, and keeping the dungeon as a living ecosystem that is constantly adjusting to changes in the environment (i.e. the intrusion by groups of adventurers).


A massive dungeon as the cornerstone to a campaign is not for every group. To be honest, as a DM I would struggle with running an entire campaign focused around a single dungeon without getting bored. But others find that a megadungeon represents the core of what they like most about the Dungeons & Dragons game.

Running a megadungeon in 5E will require some work, but it is definitely something that a DM can accomplish with very few changes to the core rules. As with many elements of old-school play, the key is in the approach to the game, not entirely in the rules themselves. A group willing to embrace such a campaign premise can have as much fun as the players who explored Gary Gygax’s original Castle Greyhawk dungeons.

3 thoughts on “D&D 5E – Old School and Megadungeons

  1. I’m really looking forward to it. I’ve got both the original Undermountain boxed sets (and associate sourcebooks, like Skullport), and I’ve used them extensively in previous campaigns. So I’ll definitely be picking this up.

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