Building a Modular Megadungeon: Design, Challenges, and First Impressions

 The dungeon in my campaign is created by a Dream Worm, so I thought it would be a great opportunity to experiment with a modular dungeon. The idea is that every time the players leave, the dungeon reconfigures itself based on their dreams and fears. Additionally, random events can trigger shifts in the module layout during exploration.

Designing the Modules

To simplify the process, I decided to make square modules. I then had to determine how many rooms each module should have and how many modules would make up each floor.

Module and Room Count

  • I settled on 12 modules per floor to ensure a good variety of layouts without making the combinations too predictable.
  • Each module contains between 8 and 15 rooms. Initially, I considered 30 rooms per module, but that would result in 300 rooms per floor, making exploration too slow. I want my players to move through multiple levels, so I reduced the number.
  • For reference, adventures like The Hole in the Oak and Against the Cult of the Reptile God feature around 50 rooms, which players can explore in about four sessions.
  • Page Layout Considerations: 8-15 rooms per module allows me to keep the map and random event table on one page, with room descriptions on the next.
The First 12 Modules

How the Modules are Reorganized

The dungeon's reconfiguration is completely random. To do this, I cut each module out of paper, shuffle them, and then tape them onto a board in their new arrangement. The only thing I manually decide is how to rotate them so that the connections between modules make sense. This method is not only quick but also helps maintain a sense of chaos and surprise for the players.


Theme and Subplots

Each floor has a distinct theme, but I also wanted each module to have its own subplot. I aimed for as much variety as possible, which took considerable time.

  • First, I designed all the modules in Illustrator, numbered them, and brainstormed ideas for each.
  • Since players need to map the dungeon, each module had to have a clear, recognizable feature to signal when they were transitioning into a new area. Examples:
    • A module where all the lighting is red.
    • A module with scattered velvet-blue leaves on the floor.
    • More subtle modules with architectural shifts or changes in the density of the dream mist.
  • While designing, I also took notes on potential quests and contracts that could arise from different locations:
    • A ghostly child-snatcher who takes children to live with him for reasons unknown.
    • A prophetic tree that answers questions if given the right offering.
    • A traitor to the king, hiding in the dungeon, who knows of a terrible threat lurking deeper below.

This process took me about a month to prepare the first two floors.


Layout Design in 2 pages per Module

Modifying the Event Table and Module Entries

One of the key aspects of the dungeon’s dynamic nature is how the event tables are modified as players progress. When the adventurers ascend to a new floor or return from a break, I update the modules they’re about to enter based on their past experiences.

If something scared them, like a specific enemy or unsettling event, I may alter the module entries to bring back that threat or memory. Alternatively, if they’re seeking something specific for a quest, I adjust the layout and encounters to lead them toward their goal.

For example, if the players previously encountered a terrifying Lurking Echo in one of the rooms, I might change the module’s entry to include another encounter with a similar illusion, heightening the tension. On the other hand, if they're on a quest to find a lost artifact, I could modify a module to guide them toward its location, with the entrance subtly hinting at the artifact’s presence.

This approach ensures that the dungeon feels like it’s actively responding to the players, keeping the experience fresh and unpredictable.



First Playtest Sessions

After all this preparation, it was time to see how it played in an actual campaign. Here are my initial observations:


What Worked

-The modular system works well. Players genuinely feel like the dungeon shifts and reconfigures over time.

- Mapping is difficult but fun. My players enjoy the challenge, and I occasionally check their maps to let them know when they’ve transitioned into a new module. Their maps are fairly accurate so far, and it’s a great moment when they realize how different areas connect.

-The page layout works well, but module descriptions are too long. I need to condense them into bullet points for faster reference.

- Random event tables per module are an excellent addition. They give each area a unique personality and prevent repeated visits from feeling stale. Since each module has twice as many events as rooms, the variation is strong.

And What Didn’t

-Issue with module design: I drew too many long, straight hallways with few intersections. When shuffling modules, this resulted in disconnected layouts or overly linear paths. I had to add more doors on the fly to improve connectivity.

-Too many rooms with complex interactions. I initially thought every room should have a mystery or puzzle, but in practice, it’s exhausting. The event tables also contribute to a content overload. I’ll balance this by including more empty rooms, combat encounters, and simple NPC interactions.

Conclusion & Next Steps

We’ve played four sessions so far. In the latest session, the players returned to the surface to resupply—only to find that the dungeon had changed. This was a huge moment for them, reinforcing the idea that the dungeon is alive and unpredictable.

So far, I’m happy with the modular system. There are some things to tweak, but overall, the design is achieving its goal: a shifting dungeon that the players must explore and slowly understand over time.

Upcoming Changes & Improvements

  • Improve module connectivity (fewer dead ends and isolated sections).
  • Make descriptions more concise with bullet points.
  • Balance content density (fewer complex rooms, more downtime areas).

I’ll keep updating as the campaign progresses!

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