A megadungeon obviously is a very big dungeon. But there’s more than that, much of it intertwined with the early history and playstyles of the roleplaying hobby, whose foundation lays in three major megadungeons: Dave Arneson’s Castle Blackmoor, Gary Gygax’s Castle Greyhawk, and Rob Kuntz’s El Raja Key.

Based on those historical sources, a megadungeon tends to be a large dungeon with ten or more levels. It tends to have intricate interconnections between the levels, and with the surface. It’s a place that can support a whole campaign worth of exploration. Matt Finch focused on the latter element when he offered his own definition of megadungeons, saying that megadungeons are “created for use in repeated adventures”. He said that these “flexible environments” could support many sorts of play, allowing “freedom of action” rather than focusing on a single mission. Though they might have a finale, Finch says that a conclusion isn’t required in a megadungeon — and that defeating a final encounter definitely isn’t. Megadungeons aren’t meant to be cleared out, just experienced.

Because Blackmoor, Greyhawk, and El Raja Key have never been fully published in their original forms, megadungeons seemed a will-o-the-wisp in the early industry, but now, 50 years on, there are many megadungeons available for play. Here are some of the most notable.

1. Tegel Manor (Judges Guild, 1977). The haunted house of Tegel Manor definitely isn’t a typical megadungeon since it’s largely set on one level (other than some tower interconnections). But, as revealed by the cover of the original release, it’s huge: regularly counted as having more than 250 rooms. Granted, many were blank in the original edition, requiring a GM to fill them in, but this was nonetheless the industry’s first example of what a mammoth dungeon-campaign-environment might look like. Jennell Jaquays’ The Caverns of Thracia (1979) and Dark Tower (1980), also from Judges Guild, offered other looks at near-megadungeons in the early industry, with the latter particularly interesting for its intricately interrelated dungeons and towers.

2. T1-4: The Temple of Elemental Evil (TSR, 1985). Gary Gygax’s epic Temple of Elemental Evil is another massive dungeon from the early industry that’s remembered fondly, but which wouldn’t necessarily stand up to a modern definition of megadungeon, in part because it has a very definite finale that’s the thrust of the whole adventure. Nonetheless, it contains four large levels plus four connected demiplanes, which together comprised the largest dungeon TSR had ever published up to that point.

3. WGR1: Castle Greyhawk (TSR, 1990). Though Gary Gygax’s original Castle Greyhawk has never been published (and obviously never will be at this point), there are numerous variants, most of them produced after-the-fact based on snippets of lore from the original. The first of those worth considering is WGR1: Castle Greyhawk. It was also the earliest attempt to publish a genuine megadungeon in the classic style: the designers managed to cram 1,000 rooms into 128 pages, depicting interconnected towers and dungeon levels.

There have been many returns to Greyhawk over the years. WotC’s Expedition to the Ruins of Greyhawk (2007) revisited TSR’s published version of the Castle. Meanwhile, Gygax oversaw the creation of a new version of the Castle with Troll Lord Games as Castle Zagyg (2005-2008), a project that was unfortunately incomplete at the time of Gygax’s death and then abruptly canceled by his wife. Joseph Bloch’s Castle of the Mad Archmage (2010) is essentially a continuation, written to support Castle Zagyg and to match memories of the original.

4. The Ruins of Undermountain (TSR, 1991). Though we have never seen the megadungeons of the earliest creators of D&D, we have seen megadungeons from other early designers, most notably Undermountain, the megadungeon of Ed Greenwood, creator of the Forgotten Realms. Sort of, as it turns out that The Ruins of Undermountain (1991) very quickly deviates from Greenwood’s own maps, to instead use maps from Dave Sutherland’s Empire of the Petal Throne game!

Nonetheless, Undermountain is perhaps the most extensive megadungeon ever published, thanks to its expansion in The Ruins of Undermountain II: The Deep Levels (1994), The Lost Level (1996), Maddgoth’s Castle (1996), and Stardock (1996) — some of the latter by divers hands, and so even further removed from Greenwood’s original design. It’s also of note for being located beneath a city, rather than the ubiquitous castles of the early industry. Undermountain has been revisited in more recent times in products such as Expedition to Undermountain (2007), Halls of Undermountain (2012), and Waterdeep: Dungeon of the Mad Mage (2018).

5. Rappan Athuk (Necromancer Games, 2001). Another classic megadungeon from the ’70s comes courtesy of Bill Webb. Because he published it through his own companies, “The Dungeon of Graves” may be one of the most authentic classic megadungeons ever — though it’s continued to expand and evolve over time just like Undermountain.

It’s a dungeon renowned for its deadliness. The original was published in three books for the d20 system totaling just more than 200 pages: R1: Rappan Athuk: The Dungeon of Graves: The Upper Levels (2001), R2: Rappan Athuk: The Dungeon of Graves: The Middle Levels (2001), and R3: Rappan Athuk: The Dungeon of Graves: The Lower Levels (2002). It has since been republished a number of times, mostly in “complete” forms, with Rappan Athuk (2018) for D&D 5e being the most recent, running 650 pages!

6. Ptolus (Malhavoc Press, 2006). Monte Cook’s Ptolus is best known as being a megacity, but there are also intricately connected dungeons lying below. Only a small number of them are entirely detailed, such as The Banewarrens (2002), but then you could say the same of Tegel Manor. Overall, Ptolus probably offers more of a framework for megadungeon play than a megadungeon proper, but given the scope of the overall product, it would be a shame not to mention it. Recent releases of Ptolus (2020) and The Banewarrens (2022) have converted the classic d20 releases to D&D 5e.

7. DCC #51: Castle Whiterock (Goodman Games, 2007). Obviously, Castle Whiterock harks back to primordial megadungeons such as Blackmoor and Greyhawk, just based on the name. The design does too, with 15 main levels and several “sub-levels” — the latter a common element of megadungeons the demonstrates the organic nature of their interconnected design. Though there are many quests linked to Castle Whiterock, that doesn’t undercut its usage as a campaign environment.

8. Stonehell Dungeon (Self-published, 2009). Today products like Rappan Athuk and Castle Whiterock are considered by many to be part of the OSR movement, but there are also a few megadungeons to come directly from the fan-oriented side of the OSR, designed by the players who first formed the OSR communities on the internet and created their own products without much concern for whether they were commercially viable. Michael Curtis’ Stonehell Dungeon for Labyrinth Lord was one of the first and most successful: in part because of its, tight and terse descriptions, all laid out on two-page spreads. Stonehell Dungeon: Down Night-Haunted Halls (2009) only detailed the first six levels of the megadungeon, but was eventually followed by Stonehell Dungeon: Into the Heart of Hell (2015), completing the megadelve. A few side-levels are also available.

9. Barrowmaze (Self-published, 2012). The other top megadungeon to come out of the less commercial side of the OSR is Greg Gillespie’s Barrowmaze, also for Labyrinth Lord. It’s smaller than many, with the original PDF just running 84 pages, but that was soon expanded with Barrowmaze II (2012). The result may be one of the most-run delves in the OSR, later consolidated into Barrowmaze Complete (2014) and inevitably converted for D&D 5e (2017).

Gillespie should be the goto name in modern megadungeon design as he’s also released The Forgotten Caverns of the Archaia (2017), Highfell (2019) and Dwarrowdeep (2022) to expand his expertise in the area. Unfortunately, he caused considerable controversy in his Dwarrowdeep Kickstarter when he announced that it would be “steeped” in “Anglo-Saxon history” and “devoid” of “woke nonsense”.

10. Eyes of the Stone Thief (Pelgrane Press, 2015). Every megadungeon in this list was built for some variant of the D&D game, but Eyes of the Stone Thief is the most distantly related, as it’s for 13th Age (2013), itself inspired in part by D&D 4e (2008). Eyes of the Stone Thief is also relatively unique in its goal of building a whole campaign around its megadungeon, rather than just using the megadungeon itself as the heart of the campaign. Oh, and dungeons in the world of 13th Age are living, moving predators.

A few other megadungeons almost made this list:

The I-Was-There-First Award: Blackmoor (Judges Guild, 1977). Dave Arneson’s megadungeon was obviously the first, but it would take decades for a comprehensive version of the megadungeon to appear. The First Fantasy Campaign (1977) offered the first maps of the dungeons, but the description just listed monsters and treasures. Many years later The Dungeons of Castle Blackmoor (2006) from Zeitgeist Games offered 300 pages of description for 20 levels, but it was late both in the history of the industry and in the d20 boom, so it received little attention.

The We-Can-Rebuild-It Award: Maure Castle (Paizo, 2004). Rob Kuntz’s Castle El Raja Key is the other classic primordial megadungeon. He sort of rebuilt it from scratch in a number of articles from Dungeon magazine, starting with “Maure Castle” in Dungeon #112 (July 2004). It was well-received, but some combination of the fact that it was a rebuild and that it’s only appeared in a magazine have kept it from achieving greater attention.

If you want the actual El Raja Key, Kuntz has made his notes and maps available as part of the El Raja Key Archive (2016), a CD-ROM.

The Missing-The-Point Award: World’s Largest Dungeon (AEG, 2004). The World’s Largest Dungeon was built to create a delve that included every monster from the D&D SRD. It may be more of a stunt than a coherent dungeon, but the fact that it’s laid out on a single level also moves it away from the modern definition of a megadungeon.

The Hat-Trick-Award: Dwimmermount (Autarch, 2014). James Maliszewski’s Dwimmermount could have been the third great megadungeon from the OSR, but it ended up being one of the first major problematic Kickstarters for the industry, which dramatically reduced enthusiasm. When it was released, it also released less enthusiastic review than Stonehell or Barrowmaze.

The Level-by-Level Award: Emerald Spire Superdungeon (Paizo, 2014). Megadungeons don’t have to be the product of one mind. In fact going back to the primordial Castle Greyhawk, discrete levels such as the Bottle City, the Garden of the Plantmaster, and the Machine Level are some of the best known elements of that delve. However, there’s obviously a need for some amount of coherency and interconnectiveness to make a megadungeon shine, and that’s where Paizo’s Emerald Spire fell down. It’s the product of a lot of different authors, each creating a single level. Readers say some of the individual levels are great, but there’s been less acclaim for Emerald Spire as a coherent megadungeon.

This article was originally published as Advanced Designers & Dragons #71 on RPGnet. It followed the publication of the four-volume Designers & Dragons (2014) from Evil Hat and was written to be a part of the upcoming Designers & Dragons: The Lost Histories and The ’10s.

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