(Continued from Megadungeon Mastery II: Rise and Fall of the Great Underground Empire.)

How large is it? Relatively large, apparently.
As often happens when trying something new, when I decided to build my first megadungeon I said to myself, “I’ll try to be different and original and do things my own way!”
Naturally, this led to problems.
Right now I want to focus on matters of scale. Ironically, this sounds like a brief subject but actually covers a lot of ground. I’ll start with a few things I learned about designing and drawing megadungeon maps.
1) Don’t make your levels too large. In designing the dungeons beneath the Chateau d’Ambreville, I sketched out a huge, elaborate castle and decided to put entrances under various towers. In order to fit all these entrances onto one level, I printed out maps on 11″x17″ sheets of paper, then folded them in half so they could fit into my binder. But there were problems!
• 1a) If you fold your maps in half, they’ll fray and tear along the fold. This is no fun, and requires lots of fiddling with adhesive tape to keep them together. It’s better to make smaller sub-levels that each fit onto one sheet of paper, and connect them with long corridors.
• 1b) Large maps can get out of control. Once you’re trying to fill in a huge map, you may realize that now your themed level now has 200 rooms and after filling in 50 of them, you’re stumped as to what to put in the other 150.
• 1c) If your levels are too large, it’s hard to keep track of what’s where. This can be important when trying to figure out how nearby dungeon inhabitants will react to the PCs and their trail of theft and murder! (I’ll include more detail on these issues in a future blog post.)
Note that you can always provide more level-appropriate encounters by making an additional level — a “sub-level” — at the same depth, connected to the rest of the dungeon by a single stair or passage. Multiple themed sub-levels can be strung together to generate the effect of a huge dungeon level while avoiding many of the problems inherent in huge dungeon levels.
2) Use graph paper with large squares. Maps are about more than walls and doors! They’re an invaluable resource for marking down other details: furniture, whether doors are locked, tracks on the floor, light sources, odors, etc. And at five or six squares per inch, there’s just no room for those details. Even the traditional four squares per inch may feel a little cramped. Sure, you can note these things on your map legend, but if too much of this information is written in the legend rather than drawn on the map, it’s far too easy for key details to slip your mind in the heat of play.
* * *
I’ve mentioned that the number of rooms on a level is significant. This isn’t simply a matter of aesthetics. Rooms contain monsters and treasure; in a sense, they’re buckets of XP for the player characters to fill themselves from. Furthermore, each deeper level is supposed to have tougher monsters and bigger treasures (on average) than the previous level, so that higher level PCs are encouraged to keep delving deeper to get the XP needed to continue leveling up at a decent rate. So each level should contain enough treasure for all of your PCs to level up if they clear it out — plus some extra to account for PC death, level drain and hidden caches that they fail to discover. Too little treasure and they can’t level up; too much treasure and they’ll hang around on that level instead of going deeper. (The specifics of how much XP comes from monsters and how much comes from treasure varies by edition.)
The problem here is that the size of the level roughly determines the number of encounters, which take time at the table and increase the chances of losing XP to PC death. So if you make a really big level, you either need to add more treasure or reduce the number and/or intensity of the encounters.
Reductio ad absurdum: You decide that you need to put 20,000xp worth of treasure on the first dungeon level to ensure your PCs can level up. You’ll distribute this roughly according to the OD&D guidelines: 1 encounter per 3 rooms, half of all encounters have treasure, one-sixth of rooms without encounters have treasure. (This comes to treasure in roughly one-quarter of all rooms.)
• In one instance, you design a 4-room dungeon level containing a single treasure: a 20,000gp gem. Unfortunately, there’s no worthwhile combat challenge available for this purpose; either you’re giving away treasure like Monty Haul, or the monsters are strong enough to kill the PCs (so why did you put this encounter on the first level?), or it’s so well-hidden that no one will ever find it. Failure!
• In another instance, you design a 4000-room dungeon level with 1000 treasures, each averaging 20gp. Aside from the difficulties of designing over 1000 first-level encounters, it will take your players forever to wade through enough of these encounters to get an appreciable amount of experience, and they’re bound to lose PCs faster than they can bring in treasure to level up. Failure!
So the amount of treasure on a dungeon level needs to be enough to level up all of the PCs, as modified by the number of encounters required to obtain that treasure.
You should be able to calculate this by determining two key variables: how many sessions you want to run before the PCs level up, and how many rooms your group typically gets through in one session. The latter number will vary a lot, of course; sometimes the party manages to cover large expanses of the dungeon by wandering from empty room to empty room, while at other times the party runs right into a big set-piece battle where clearing out a single room takes up the entire session.
So if your party averages four rooms per session (for example) and you want them to level up roughly every ten sessions, if one in four rooms has treasure in it, then you want ten of those treasures to be enough to level up. Moreover, if the party tends to miss about half of the treasures they run across (because the treasures are well-hidden, or they use up half the treasure on raise dead spells, or whatever), you could ramp up the treasures further, so that only five treasures will suffice to level up.
And remember: what’s right for your group isn’t necessarily what’s right for other groups. Some players enjoy mapping complicated dungeon levels, seeking out carefully hidden treasures or unraveling intricate tricks and traps. Others don’t. Unless you have access to a sufficiently broad player base that you can find players who like playing exactly what you want to run, you need to adapt your dungeon design to the needs and desires of your players. After all, the fun is the thing!
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