• Aaron K

Underwater Dungeons!

Hey Reader!

So I'm starting a new series as I externally process the dungeons I create for my players. This will be a mostly system-neutral series on the blog (as I've designed dungeons for several different systems), and today we are looking at a dungeon that I recently ran for one of my groups that is playing a "Sprites Campaign" in Zurn: the whole party is comprised of different types of sprites, with the tallest of them being only 10" tall. The result: you can have a lot more fun when building the world, let alone dungeons.

We will be looking at five things that I considered when building the dungeon, some of which will be mainstays across this series, though their application will look different based on the setting.

I. Choose a Theme

This should be obvious when building a dungeon, but you'd be surprised at how few people talk about this: you should have a theme for the dungeon. Throwing a bunch of monsters in an underground (or in this case, underwater) adventure is fun, but it will result in a dungeon feeling a bit lackluster.

Themes help to tie things together, as well as give clues to the party on how to solve traps and puzzles (more on that in a minute). They also help immensely in sifting through all of the monster profiles to determine what you should put inside your dungeon (if any - more on that later).

But a theme is not "an underwater dungeon" or "a dragon's lair": those are kinds of dungeons, not themes for dungeons. A "theme" can take various forms, but they all do one thing: to serve as the "diamond" that is the dungeon, and each encounter then acts as a different "facet" of that diamond.

So your theme could be tied to a virtue or vice, designed to test courage, fortitude, or greed of those that enter. You can also center it around a saying, inscription, or even a scrap of cloth from a past traveler who was trying to unravel the mystery of this derelict place. I like this setup as 1) if it's an inscription it shows that the local clan valued the theme as well, and 2) having an inscription or cloth with the writing on it allows you to give your players the theme upfront before they enter, making the theme's presentation natural.

For this dungeon, I chose the theme, "In Darkness Hides the Light," and it's designed to test the fortitude and resourcefulness of the players through darkness and light. Of course, both of these concepts of darkness and light have metaphorical meanings too: we say that you are "illuminated" when you learn something, and portray moral goodness and badness with light and darkness respectively. So the theme gives us lots of room to work, which is the sign of a good theme.

II. Atmosphere

The atmosphere of the dungeon includes two things: the setting for the dungeon and the literal atmosphere. Most of the time your atmosphere will be "air" in some form or other, but there are many choices. For the underwater dungeon we are using the atmosphere is "water," which means water breathing is something the party needs to plan on (through a spell, magic item, etc.), and they have to guard whatever that is.

But once you get out of a medieval fantasy environment the world gets a lot larger in terms of atmosphere. Consider a nitrogen-based atmosphere on another planet: oxygen-breathing creatures will need a breathing apparatus, but this would also likely change the temperature, giving you options for elemental damage purely due to the atmosphere. This sets a timer of sorts: the longer you take, the more it's going to hurt.

And of course, there's always the vacuum of space: no atmosphere.

The setting also includes things that most people consider the theme: the "dragon's lair," the "ancient tomb," and "an underwater derelict ship" are three good examples of this. Each sets the tone and mood of the dungeon, helping your players get into a mindset that reflects where they are. So think through the atmosphere: what does the place feel like, and what surrounds the players?

In this case, we are using an old kappa fortress that was abandoned/taken years ago, and the place is now inhabited by grindylows and their pets. So it should have a tomb feel much like Indiana Jones artifact-hunting escapades. Just with tentacled guards instead of Nazis.

III. Encounter Selection

This refers to the encounters in your dungeons, of which there are three kinds: traps, puzzles, and combats. Traps are things that stop the players and remind them that they are in a dangerous place. The goal of a trap is not to damage the characters (though they very well may): it's to remind them of the threat of damage to them. It heightens the idea that we're in a dungeon: this is not a normal quest. So if you have a party that is good at looking for traps and disarming them, don't fear: that's a good thing. We're feeding their paranoia, even if they suffer no damage from them.

Puzzles are my favorite for several reasons. First, for those of you who don't know, my initial life goal was to become an attorney, so I spent a lot of time preparing for the LSAT. The Reading Comprehension section didn't go very well (hence why I left that dream), but the Logical Reasoning (or "Logic Games") section, which is widely considered the hardest part of the test, I got perfect scores on across dozens of practice tests and the actual test I took. So puzzles let me live out my love of logic games. I hope my players are cool with that.

The other thing they do, though, is they take the game away from math and into the realm of reasoning. Puzzles make sense in-world: if I want to keep an intruder out, I put a combination lock on something, or password protect my internet. For those that know the answer they can access it. For those that don't, it keeps them away.

That's what puzzles do: in-world they should keep out intruders or would-be treasure plunderers. Out of character, they validate the players: you can't solve a puzzle just by rolling high. You have to do something right, and you validate them when they get the puzzle right. So use puzzles: they make players feel good, and change the focus of the game for a short time.

And finally, there are combats. It should be noted that you don't need combats in a dungeon (and I'm currently working on a dungeon that doesn't involve any); think of the opening sequence in Indiana Jones: Raiders of the Lost Ark. There are no combat encounters in that dungeon: it's just a series of traps. In The Last Crusade we get a "dungeon" comprised purely of traps and puzzles leading up to the Holy Grail.

But most roleplay game are built as combat simulators with most of the rules based around combat prowess, so your players are probably expecting combat. So be ready with combats in your dungeons if that's more of what your group enjoys. To this end, plan your dungeon's layout around combat encounters.

Empty rooms with no cover or life in them make for dull encounters, so plan on having something(s) in the room to add a bit of variety and strategy. Think about how your NPCs will use these to their advantage: they are the home team after all, so they should know the terrain and take advantage of the terrain often.

Also, don't have NPCs fight to the death unless there is a good reason for it (they are a construct, undead, or other creature where preservation of their life force is not a goal). They can always retreat deeper into the dungeon, surprising the adventurers in the final "boss battle," making it harder.

In this case, the grindylows have tamed pike and crabs over the years, so the party encountered both of those in the dungeon alongside the grindylows. The party also faced a heat trap - the room's water level fell, giving them a space that had no water (designed by the kappa originally to keep large fish at bay, but the grindylows can breathe in both air and water, so alas for them) that then heated up. So the trap centered around a boon for the party (air filling the room instead of water) turning out to be a vice (the room got too hot). And, consistent with the theme, "In darkness hides the light": the trick is that they need to put out the lights that are emanating the heat into the room.

And one final note under combat encounters: tie them to a puzzle or trap. Do you know what's harder than fending off a bunch of grindylows with knives? Doing that in a room that constantly goes dark thanks to a light-absorbing mushroom in the middle of the room. The trap augments the combat, giving the party two things to do at once: fend off the attackers while solving the trap.

Bonus points if the party is fighting while navigating a trap while trying to do the dance to get the door open (Combat + Trap + Puzzle).

IV. Color Code

This is a newer thing I've been experimenting with, but I really like it so far. Color code your encounters so that your party knows how far they have progressed. There are many ways you can do this (does the local flag have a progression of colors on it? Does the local deity have a symbol with different colors tied to it?), the most simple being going in order of the colors of the rainbow. This gives you seven colors, thus seven levels of encounters, which is a decent size for a mini dungeon crawl.

What it does subliminally, though, is it boosts party morale. If you've ever been in a dungeon where it seemed like things were dragging and you were making no headway (I was once in a dungeon as a player for four sessions, which was a looooong time, and the GM even cut out a few sections so that we could move on with the plot), you know how important morale is during a dungeon crawl. Color coding gives your players a diagnosis of how far along they are.

Now you can do colors various ways. Perhaps the rooms are different colors (what I'm doing in my underwater dungeon, because kappas love color and grindylows are color-blind, so they wouldn't mess up the color scheme), or the creatures or guards are in different colors (your common footmen will dress in one color, but your inner guard may have different livery). This can be subtle, but it signals to your players how successful they are being, and as the colors change morale grows.

I personally like scaling up to red as the final color, in part because red is my favorite color, but also because it signals "danger." This also means that, if you are color coding the inhabitants, putting a red dragon at the end of the dungeon works for the color scheme. But yes - choose a color scheme, and use it to signal to your players.

V. Does It Make Sense?

Why would a given culture have spinning blades in the hallway? Why would a high-traffic area have pressure plates that set off dart shooters? Why would there be a gang of trolls in the room right before the core of the lair? Lots of reasons, you just need to figure out what those reasons are.

Do a bunch of ghosts with no mass or fliers who don't touch the floor inhabit the dungeon? Then they won't set off a pressure plate, so it's perfectly fine to have them in a dungeon. Do the spinning blades spin 3 feet off the ground, deftly missing the inhabitants that are under 3 feet tall but chopping up intruders who are far larger than they are? There are tons of reasons why any trap makes sense, but the question is does it make sense with the theme that you are using? Does it make sense for the creatures that you added? Does it make sense for the atmosphere and setting (underwater darts sound awesome, until you realize that a pressure plate on the floor is the wrong trigger as people will likely be swimming through the dungeon instead of walking).

For our dungeon, this dungeon was taken by the grindylow clan from a former fey civilization, so we have two things to weigh: did it make sense for the kappa, and does it still work for the grindylows? So keep in mind that if you have creatures that have crept into a formerly built place, it has to make sense for both.


Not all of these ideas are unique to me; for more great ideas (like the integration of verticality into your dungeons, which we will discuss in a future dungeon design post) check out this video by Questing Beast on YouTube: he has really good stuff. I hope that this has been of use to you, and may your dungeons be that much cooler!

Until next time,


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