In the early 70s, as Gary Gygax co-created Dungeons & Dragons, he played the game seven times a week. He wrote, “As I worked at home, I did not schedule play sessions, but when a gamer or two dropped in on a day, I made haste to finish immediate work and put on my DM’s hat. Evening games with the regulars were generally scheduled a few hours or a day or two ahead.” Weekend games included 10 to 20 players.

How did Gary referee his ongoing Greyhawk campaign for a cast of characters that changed completely from session to session? (Nowadays, dungeon masters like me stretch to keep one or two absent PCs from upsetting our game’s plot.) How did Gary create material for so many games? (I always scramble to prepare one game a week.) In 1974, as Gary focused on publishing D&D, he began sharing campaign duties with a second referee, Rob Kuntz. (I would never dare attempt collaborating on a campaign with a second dungeon master.)

The secret to all these feats lay in the design of the 12+ level megadungeon under Greyhawk Castle.

Level 1 of the dungeon under Greyhawk Castle photographed in 2007 by Matt Bogen

Like Gary, D&D co-designer Dave Arneson ran a campaign for a large and fluctuating pool of players. Dave managed with his own megadungeon below Blackmoor Castle.

Every game session mounted a new expedition into the dungeon, so the particular cast of characters never mattered. These megadungeons enabled a style of episodic play that made those original campaigns manageable. Al from Beyond the Black Gate described the advantage well. “The scale and scope of the Megadungeon makes it friendlier to episodic play than for the more common ‘clear the dungeon’ style of play. The Megadungeon is the perfect place for short, engaging adventures in a compelling environment (even if those sessions just happen to combine into one long campaign).”

Gary never needed to adjust a session’s difficulty to party size or experience, because players could chose a difficulty by choosing how deep to delve. The game awarded more gold and experience to players who dared the lower levels. See “Why D&D characters get tons of gold and nowhere to spend it.”

Today, we tout the value of sandbox play, where players can take the game in any direction they want without feeling corralled by some story in the DM’s head. DMs tend to expect sandbox play to require improvisation and in-game adjustments. For instance, the designers worked to make much of the Princes of the Apocalypse adventure play as a sandbox. When I talked to dungeon masters about running it, we always focused on the challenges of preventing the PCs from straying into certain death.

The megadungeon let Dave and Gary to act as referees rather than dungeon masters—that term would not see print until the game’s second supplement Blackmoor in 1975. They could run a game entirely from notes, wandering monster tables, and the whims of the dice. If megadungeon referees choose, their campaigns never needed improvisation or in-game meddling. This gives players more control over their characters’ fate—more player agency—than in typical modern games.

Gary kept preparation manageable. He wrote, “I usually made one-line notes for my dungeon encounters, from around 20 to 25 of same for a typical level done on four-lines-to-the inch graph paper—a few more on five-, six-, or seldom used 8-line graph paper. The other spaces were empty save for perhaps a few traps or transporter areas and the like.” He and Rob Kuntz kept notes. “When the encounter was eliminated I simply drew a line through it, and the place was empty for the foreseeable future. I’d give Rob the details of any session he was not at and vice versa, so we winged all of [the campaign management]. Sometimes a map change and encounter key note of something special in nature was made, but not often.”

On page 4 of the original, brown book, The Underworld & Wilderness Adventures, Gary made a megadungeon a requirement for play. “A good dungeon will have no less than a dozen levels down, with offshoot levels in addition, and new levels under construction so that players will never grow tired of it. There is no real limit to the number of levels, nor is there any restriction on their size (other than the size of graph paper available). ‘Greyhawk Castle,’ for example, has over a dozen levels in succession downwards, more than that number branching from these, and not less than two new levels under construction at any given time. These levels contain such things as a museum from another age, an underground lake, a series of caverns filled with giant fungi, a bowling alley for 20’ high Giants, an arena of evil, crypts, and so on.”

The Doomvault from Dead in Thay

Although folks don’t play megadungeons much now, the places remain uniquely suited to episodic play with multiple parties exploring the same space. Scott Fitzgerald Gray ingeniously used those strengths when he wrote the adventure Dead in Thay for a D&D Encounters season. The Encounters program lets players drop in a game store for a night of D&D. Different players may come for any night of play, shuffling each table’s adventuring party.

At first, the program managed these fluctuations by requiring every table to play the same episode in the adventure. The format limited players’ choices to battle tactics.

In Dead in Thay, each table launches their own, unique foray into a megadungeon called the Doomvault. By creating the sort of dungeon that made the Greyhawk and Blackmoor campaigns work, the season rediscovered some of the format’s advantages: episodic play for whoever attends, the freedom of a sandbox where players can change the environment, and manageable cooperation between dungeon masters.

When Shannon Appelcline looked back on the adventure, he wrote, “For the most part, Dead in Thay is a classic, old-school dungeon crawl of the sort you could find back in the ‘70s. However, it presents a more mature, more active dungeon, where the rulers of the realm can react to the players’ actions…and where the players themselves could change an environment.”