Populating the mega-dungeon part two: Magic (and story) is your friend

"I don't think this spell does what you think it does!"

Magic is your friend

If you don’t feel like working out a vague ecosystem, just say the dungeons magical. Have the players come across some dedication written by a long dead wizard who forged this magical space. 

Magic can be the answer to almost everything. 

Magic is the Dungeon Master’s best friend.

You don’t need a fully worked out food chain. That’d be an awful lot of work and kind of nuts. There’s no way so many apex predators could coexist in such a small space, there wouldn’t be enough for them to eat. You’d need a dungeon tens of miles across. 

You only need is to establish the semblance, the impression, of an ecosystem. 

...just filled with ravenous man-eating monsters, demons, and pits of green slime.

Backfill a backstory 

Another way to add variety when characters are plowing through an area dominated by one monster type is to add backstory. Sometimes, the need for this only becomes obvious when you are populating an area. 

If the dungeon is old and our orcs from the example are not the original inhabitants, you can layer in elements rom earlier eras. Perhaps the orcs have moved into an old arena, and there are trap doors and a labyrinth beneath for monster holding pens, along with weapons, unspeakable horrors, and undead gladiators. Or they’ve occupied an old prison, or an old dwarven forge. That can spark all kinds of ideas: dangerous abandoned equipment, elemental powered furnaces, cryptic murals, cells with immortal prisoners, torture devices containing undead victims, wall carvings that hint of deeper treasures that the characters are seeking. 

Adding an earlier purpose creates entirely new adventure hooks. Players can take them or leave them. I try to throw in a lot, because many (most) won’t intrigue. But when you have a hit, mine it like a Hollywood executive exploiting a time honoured franchise!

I recommend mega-dungeons be abandoned, repurposed spaces. If you work out the story for the duengon’s earlier inhabitants, it gives you direction and purpose when seeding in elements. The space is imbued with an underlying logic that smart characters can suss out, allowing them to piece together the past, possibly leading to greater rewards.

Getting all that to work can be challenging, and it’s easy to overcomplicate things. That’s what do: I plan overly ambitious backstories that won’t conclude until… uh… maybe level 10, and I start setting them up on level 2. 

By the time I get to level 10 I guarantee I’ve forgotten what the heck I was doing on level 2. 

Fortunately, the players will be your guide, letting you know what story hooks to nurture, and what to let fall away. They won’t remember the threads left dangling because those threads didn’t interest them in the first place.

This also argues for the living dungeon. 

"What will suddenly introducing all this loot into the local economy do for inflation?"

The living dungeon 

Don’t finish the mega-dungeon before you start. Trust me no this. Megadungeons are big, sprawling feats of imagination, almost herculean tasks, and if you try and do it all before players go through, you risk investing too much into a dead end path.

All you need are the first 3 or so levels plotted out. If you’re really ambitious, you might rough out some lower level maps, but you don’t need to plot everything out yet. Plunk in a few monster possibilities so you have some inspiration at hand in case the players get ahead of you.

Instead, listen to your players as they progress through the first 3 levels. See what interests them, and what they couldn’t care less about. Have a bunch of story seeds that you can plunk in, and a vague idea of the resolution, and see what characters latch onto. The mysterious lost tome of the Necromancer? They couldn’t care less about. But the Treasure of the Gorgon Queen? They’re all in! 

Pivot to what the characters are intrigued by and alter the dungeon to fit. This doesn’t mean abandoning what you like. You’re just emphasizing elements you already had, to pull the players in more effectively. 

Remember that the dungeon is a shared space, living in the imagination of both DM and players. Everyone has to be interested, if you want to keep your magic imaginary realm alive. 

Another issue is that players level up much, much, MUCH faster than in AD&D. You needed a lot more treasure (you got XP points for treasure back then) and monster kills to advance then. To reach level 2, some classes needed 3,000 XP. Now, everyone only needs 300 XP. 

This means your characters may advance in levels musch faster and more erratically than you might be prepared for. You then need to buff up the dungeon denizens as players have outpaced the challenges you originally set.