Streamlining My Megadungeon Design

I like to have things simple and precise. A megadungeon would seem to defy that, but I'm going to try anyway. Here are some things I'm thinking as I pound out a draft of the place.

I'm not going to describe each door. For most doors, I'm going to leave it to the GM to determine the nature of the door. I'm thinking that the beginning of the book could have 6 or 12 options for doors you could encounter. For example:

(1-2) Door is wide open. It looks like someone else secured the door with stakes to keep it from shutting; (3-5) The door is shut, but is otherwise unremarkable; (6-7) the door is shut and swollen, requiring a might check to open; (8-9) the door is shut and locked, requiring a might or thievery check to open; (10-11) the door is locked and trapped; (12) the door is magically sealed.

Any time you encounter a door, either roll or pick one. Or, use likelihoods starting from the beginning of the list and moving down. If it indicates that it is trapped, then roll for the type of trap present (and this could be a magical trap); if it is magically sealed, the GM can decide whether it needs a key, a password, or a dispel to open it. It could be a key that he's already given the party (they started with a magic key that opens several special doors) or it could be a whole side quest the GM adds. I want there to be flexibility for GMs to personalize the dungeon without asking them to do much prep work. It should be a zero-prep experience - you can improvise how and why it works using imagination, the rules for likelihoods, and your own personal goals for the dungeon experience.

This still leaves open the possibility of special doors throughout. I could decide that a door is a monster in disguise, works using a series of intricate mathematical locking mechanisms, or can only be opened when the statue on the other side of the room has been turned to look away from it. The presence of the random options doesn't prohibit other inventive doors, but it keeps me from having to write descriptive text for every relatively common type of door one might encounter. The same is true for traps, pools, statues... there can be statues that do common things, and special statues once in a while that do special things.

In terms of encounter areas, I like the number ten (although maybe twelve works better because of the game...). If each area has a fixed number of encounters, I leave room for open spaces and for the GM to be creative. In looking around, I found a thread with this advice by Gary Gygax from the Dungeon Geomorphs:

Roughly one third of the rooms should remain empty. One-third should contain monsters with or without treasure (possibly selected randomly using the Dungeons & Dragons Monster & Treasure Assortment), one-sixth traps and/or tricks, and the remaining one-sixth should be specially designed areas with monsters and treasures selected by the DM (rather than randomly  determined). Slides, teleport areas, and sloping passages should be added sparingly.

This seems to align pretty well with my basic idea, which is to create maps that have 12-15 or so areas, stock ten of them, and have two or three of those be 'special' in some way, providing unique challenges or unusual encounters. I will try to make it more than 'you open the door and find five goblins', but sometimes five goblins are in a room eating, sleeping, playing cards, or on guard duty. However, not every room can have five goblins in the middle of trying to solve a trap with moving floor panels as a statue overhead casts disintegrate on those who fail to move a floor tile appropriately. The mundane encounters are needed to help keep the special encounters special, and a few 'empty' rooms give places for the GM to add to the dungeon, or to give characters places to rest. 

A megadungeon has to be a little bit of a grind to feel like a megadungeon. If you get through a level in ten minutes, it's not a megadungeon. You should have to spend a good deal of time exploring, fighting, and thinking your way through it.