I am sure most of this has been said better before, but here's what I've learned in the 6 months I've played D&D as an adult. Most of that time I've been designing and running megadungeons (or trying to). ASE is an excellent model and has great ideas for megadungeon play, but I've got a few of my own ideas below as well from running the HMS Apollyon on Google Hangouts for six sessions.
|A map from the internet - betting it's Dyson Logos'|
What is and Why is a Megadungeon?My definition of a megadungeon is single adventure locale that players will return to repeatedly over the course of the campaign. This location must then be interesting and varied enough to want to return to, contain a variety of challenges and reflect changes in the larger game world.
Another key element of the nature of the Megadungeon is that it doesn't require a reoccurring set of delvers. Players may return, but parties can change, get wiped out or wander off and the Megadungeon should be large enough to remain partially (if not largely unexplored).
How to Run a Mega Dungeon (If you're me).1) A Living Dungeon - Megadungeons have to react to and interact with the larger campaign world. They may start as static, but a great deal of fun can be had by players and a sense of accomplishment better than finding a big treasure occurs when the Megadungeon overflows into the larger campaign world, or player actions create dynamic change within the dungeon. Likewise wonder and novelty are created when the dungeon and its residents adapt to intrusion or even decide that turnabout is fair play and march out into the light.
- Factions within and outside dungeon are important. What happens when the Dungeon goblins ally with the forest goblins? Or when the local tax collectors start to get wind of the Dungeon's wealth? Does the nearest city or king send its military to contain or plunder the dungeon? In dungeon allies are helpful as well, because they provide henchmen, demand the PC's do things for them and can give new clues or rumors. Knowing what all the monsters and such want is very helpful - even if it's knowing they only want tasty surface dweller flesh.
- NPC Parties. Not only are these folks the most dangerous monsters, but they are rivals and allies. Furthermore they can move things along well. Want the PC's to move to a different part of the dungeon? Talk about how someone else pulled a bunch of loot out of there, or have the NPC's crack a door or wipe out a monster that the PC's are afraid of. More importantly, players are cautious in the extreme and sometimes get in a rut of searching the easiest rooms for scraps as opposed to delving deeper. When they find NPC party graffiti and a bunch of cleaned out rooms they have no choice. In dungeon factions can do the same. Even evidence of disturbance, and the fear that the local bandit chief will get the loot, can spur players to reckless action.
- Big consequences. It's really nice for a player to feel like what they do matters.This can be something as simple as a change in the geography of the dungeon and turmoil among the dungeon's factions and as big as causing the collapse or formation of empires above ground. Death Frost Doom is the new classic example of this, but the same sort of scenario applies when the orc tribe flees the party and learns that the nearby town of Shirebottom has only four guards, none of whom are as tough as a bugbear, or the skeleton king discovers that there are graveyards full of potential recruits just over the hill.
- Different kinds of environment - as mentioned above this makes things interesting and makes mapping easier. It also encourages sublevels and the determination of factions. Since filling space is a huge issue for a Megadungeon GM Gygaxian naturalism is a way to go. It's also the way to generate conflict and alliances among dungeon dwellers and determine what the player's actions result in long term. Basically every group of creatures needs a certain set of spaces: a dwelling space, a food source, water source, source of raw materials (as needed) a way to dispose of waste and a space to do whatever it is they do (make weapons, practice arcane rituals etc.) Food/water sources provide the best way rationale for dungeon dwellers to fight or work together. I.e. the Bugbears protect the goblins so that the goblins can farm giant grubs that they share with the bugbears, but the Jabberwocky, being a dumb and unreasonable just wants to eat all the grubs and keeps attacking the goblins' farm. There are all sorts of spaces for the players to interfere in power balances like this. Additionally if the grub farm is left semi-intact, someone will take it over because food is important. Yet none of this happens is the case of the moldy old tomb once the players loot it and destroy its guardians.
- Multiple paths and off limits areas - This has been done to death everywhere else, but it remains true. Multiple paths allow for tactical and strategic choice and easy or harder ways to move about the dungeon's subsections. Finding the optimal path to a desired space is part of the Megadungeon experience. Hence rivers, teleport pads, hangways and chutes are all rightfully popular in Megadungeons. It adds something if using rapid transport allows glimpses of other areas, like a Disneyland ride as it creates expectations and gives clues. Likewise areas blocked by locked doors, chasms, huge stone blocks and such are useful, even when the GM has no idea what's beyond them. It becomes especially nice when a way into a previously unexplored area can be opened from somewhere far away and it makes the whole place feel linked and allows pacing of areas in a non-linear manner. Steal the eyes from the idol on the 5th level and the stone sigils melt opening the way to the prison area beyond the great seal on level one and releasing the trapped demons from within. It's also important to not stage things too much, letting the players know what the dangers are at higher levels is reasonable. Trust them to realize that trying to fight the mighty sludge beast the size of a skyscraper when they're 1st level is deadly.
- Likewise as a Megadungeon the very point is that one gang of adventurers will never see the whole thing, and the dungeon keeps repopulating itself - creatures get chased up from the depths, and 'civilized' enemies find there way in to set up shop below. This means that an area may suddenly become unsafe for one group when a previous group walked through it unmolested.
- I think there are two kinds of Megadungeons, ones with an overworld (extrinsic worlds) and ones without (inclusive worlds). There's that old Borges story about the maze and the nomad chief 'the desert (or the world) is my maze', and that's how Megadungeons without an Overworld work. The town is in the Dungeon, there are no hex crawls, no escape and no other locales to worry about. The players must delve to survive as they are dungeon denizens themselves. This is how Apolloyon works and I like it for the Google+ venue as it leads to almost immediate play. It also mean dungeon politics and overworld politics are the same. In a dungeon with an Overworld there are also advantages (and the risk the players will decide to hare off and do something entirely different) in that overworld politics and powers can take an interest in the dungeon. Imagine how great a few sessions would be where the players must build alliances amongst dungeon denizens to fight the army of some jerk overlord who wanted to take the place over for himself?