So I set up a megadungeon for my Open Gaming Table. There are at least five main areas of ingress, scattered around the slopes of Mount Dis ("Mount" being relative; recall that sea level was a mile above the highest peak before dropping by a mile; the highest point in the world is still only half a mile above sea level):
- The Ruins of the Disreputable City and Mat~Sya, on the peak of the mountain. This area is too large, so I made few specific maps. There may be some locations from the first campaign or some specific new areas of interest. But mostly, anything that happens here, I make up on the fly.
- The Poison River / The Don't Drink This River (two names for the same river). This foul, undrinkable, ooze-infested river emerges from the side of the mountain. I used the Donjon random dungeon generator for a base, carved a river through it, then added a great many miscellaneous Things.
- The Tiv-Beckett Cold Iron Mine, infested with centipedes. I couldn't find any good, large mine maps, or any generators that turned up things that looked like mines, so I just did one myself. Random long, twisty passageways punctuated with occasional irregular rooms. Rails lead to lifts to the deeper levels.
- The Cave of Burning, very hot and inhabited by many fire creatures. I used Donjon's random dungeon creator again, replaced some of the walls and floors with fire walls and floors from Dungeonscape, and again, miscellaneous Things.
- The Stank Cave, populated with a myriad of funguses and other stanky things. I used Donjon's dungeon creator with the layout set to Cavernous. This is going to be massively inconvenient to draw on a battlemat.
These may or may not all be connected to each other in various ways, as well as to deeper caves within the mountain, which I may or may not have already bothered to map out.
The PCs have their choice to go to any of these locations, or to anywhere else they want to go. They're populated with different levels of challenge, which the PCs might be able to estimate by asking around with Gather Information (bartenders might have stories of entire parties of high-level adventurers entering the Caves of Burning and never coming back, or low-level adventurers scoffing at the lack of challenge posed by the centipedes in the Tiv-Beckett Mine, for example).
When the players are ready to play, I slap on the table a map of the region (including all the above locations, plus some less important things, like roads marked "to Winkle Village" or "to Omorashi border") and a stack of 8.5"x5.5" papers with bounties on them, in various handwriting and calligraphy fonts. These are the things that are posted on the bulletin board of the Adventurer's Guild. The bounties are things like:
- A sculptor wants people to bring him the spells Animate Object, Permanency, Stone to Flesh, and Awaken Construct, in any form (spell, scroll, wand, wish, limited wish, or whatever). Rewards include an Elephant Figurine of Wondrous Power, a Dread Guard as a free follower, a snarky yet powerful sword, or custom-crafted fine statuary.
- A knight of the Kingsguard (more like advisors to the king than actual guards) wants a flying mount.
- The half-ogre knight of the Kingsguard wants mermaids to feed to his elephant mount. This note is incredibly poorly-spelled, in the most childish font I could find.
- The king and his mother offer a massive bounty for "the most beautiful woman to be found in all the reaches of the cosmos", with various other caveats, for a wife.
- A knight of the Kingsguard wants the flesh of shrieker mushrooms for a cure for a plague of Spelunker's Itch afflicting the city. A pound of mushroom flesh isn't worth much, so the party may have to bring pack animals or burden themselves down with heavy loads to bring back enough to be worth it.
- Demonic creatures have been plaguing the countryside. Maps of the cave system, information on the infestation, and actually stopping the infestation altogether, all bring substantial rewards.
- Somebody, blatantly doing Tiamat's work, offers standing rewards for the heads of metallic dragons, half-dragons, dragon-descended, or Dragonborn of Bahamut, and for live female chromatic half-dragons and dragon-descended.
- The Tiv-Beckett Cold Iron Mine offers custom cold iron gear to anybody who clears their mines of centipedes, plus a per-head bounty on centipedes.
- One note written in a substitution cipher. The players will have to figure out the cipher before they even know what the quest is. If their characters roll high enough on intelligence checks, I may give them a couple letters to start them off. Because of this extra step, this bounty may be easier and more rewarding than the others.
Note that some of those bounties clearly correspond to places: the centipedes and the Tiv-Beckett Cold Iron Mine. Some of them may or may not even be accomplishable at all: the one about the wife for the king. Some are blatantly Evil: the one about killing metallic dragons. Some are blatantly Good: the one about helping cure a plague. In particular, I put no effort into balancing the rewards against the danger of the tasks. The players can freely choose which one they want to try on any given day, or not even to bother with any specific bounties and just explore, if they want.