Here are some of what I think are common myths about megadungeon play. Some are actually true, most aren't. Some of these were sparked from posts I've read recently and in the past about folk who'd tried megadungeon play and struggled or struggle with it.
It's Low Prep
No, it's not. Not at all. There is a lot of work you need to do:
At a glance, you need to:
- draw a map (preferably, with a side view, it'll help).
- stock the map with monsters and treasure.
That's at a minimum. You really need more than that.
You must map out all the areas the players could easily get to in a session or two. So if you go for Ye Olde Central Shafte Downe to Thee Utter Depthes, you need to have mapped and stocked out all the way to thee utter depthes.
You must have stats for all of the monsters the players can easily reach in a session or two, at least.
You must fill in treasure details.
You must have detailed traps, specials, tricks, oddities, and other dungeon details.
You must have decided, at least to a degree, on factions and alliances and so on.
That's simple but not low prep.
It's Fast Prep
Not really, not without a game system that's built around quick-stocking dungeons. Even then, budget some time.
Now, you can strangle off some of this like I did - by making the ruins of the castle above sitting on two dungeon levels that restricted easy access to the deeper levels, but that does impact your dungeon play a lot. You can let factions and so on sort themselves out. You can stock randomly and just let "A crazy demi-god did it" be the explanation. But there is still a lot to do. I ran a lot of sessions in my DF game before the megadungeon showed up, and I spent that time between doing megadungeon prep. We did 9 sessions over 6 months outside the megadungeon before I had enough to play on.
It's Low on Session Prep.
This is true. It's low session prep. That is, once you've mapped out a few levels, stocked them, and otherwise made it so anywhere the PCs can go today, tomorrow, or the day after are covered, you're set. You can simply sit back between sessions, generate some rumors, deal with player questions about gear, and keep the ball rolling.
But the game must be going full steam before this happens. Enough groundwork to cover multiple sessions is critical, and the game must be a going concern before prep drops off. If I could do my whole campaign over again, I'd still save the megadungeon for after the game was going for a bit.
It's For Everyone
No, they aren't. You have to really like dungeon crawling. Your players have to feel like they leave the dungeon each time wanting to come back and figure out what's behind that door from 20 sessions before, what those weird statues do, where the goddamn gnome is hiding out, how to whack the draugr without getting killed. They have to have a primary interest in the dungeon itself, and what's in it.
If that doesn't float their boat, or float the GM's boat, the game is going to suck. You won't enjoy it.
That's what I've learned from making and running a megadungeon for a while.