View Full Version : DM Help Flooding dungeon

2015-11-26, 05:22 AM
Since apparently water in D&D is terrifying, and so are ticking clocks, I would like to combine these two concepts.

The idea is as follows:
The PCs are in a rather standard dungeon crawl, with fairly easy and quick to resolve challenges. Then, just before they achieve their objective, the dungeon slowly starts filling with water.
The challenge becomes getting to the exit without drowning. Of course, many of the obstacles and monsters encountered on the way in will be a lot more dangerous now.

Mechanically, I would model this with some sort of RL-Timer (hourglass or eggtimer), with the water rising by a step with each iteration. Obviously, there would be multiple levels, with some rooms completely submerged while others are still dry (for now).

Now, I cannot think of a scenario where the flooding of the dungeon both cannot be averted by good thinking, spell selection or high rolls AND it does not feel like rail-roading. (Note: I am well aware that what I describe IS railroading and at least the "dungeon starts flooding" part is supposed to be, it simply should not feel this way)

Does anyone have ideas, experiences, comments to share about such kind of dungeon?

Some ideas I had:

Sinking ship: Probably too small for that "we need to stay ahead of the waterline" feeling. Also, can be avoided simply by smashing the walls and swimming to the surface.
Dungeon below the sea/a lake: Probably the most fitting location, provides a good excuse for all that water. Still, I can't think of a good trigger condition.
Repeating create water traps: as above

2015-11-26, 05:37 AM
An aboleth set up the dungeon millennia ago as a safe place to sleep. The adventurers blundered in and woke it up, triggering the create water traps it used so it could swim out.

2015-11-26, 05:49 AM
Potions of underwater breathing?

Or scrolls of underwater breathing, which can be spoiled by... water!

2015-11-26, 06:07 AM
I ran a dungeon once where the party was sent in to retrieve a hallowed object. With the object removed the shadows started to grow deeper and lengthen and reach out to grab at the characters. It was quite fun and had the same kind of ticking clock pushing the characters to the surface.

I don't think there is a problem with characters exchanging resources for time - but depending on edition some spells may last too long/give too big an advantage.

2015-11-26, 06:10 AM
Thoughts on this:
1. Level of players? Higher level casters may be able to Neuter this fairly quickly.
2. Do they have a Bag of Holding?

I ask the second because my immediate thought is treasure, have the traps activate just after they've reached the loot room. You've now added an extra element. If they leave it all behind they can escape quickly, if they stay and load up it'll make getting out that much harder, potentially weighing them down and meaning they have to dump it to finally escape.

2015-11-26, 11:03 AM
Right, forgot to add that. Level should not be higher than 6ish.
Water breathing is available at this level, but not reliably and certainly not for all party members. Also, drowning is not the only danger of water.

Aboleth could be fun, though I have never used one. That would also explain why all the traps and spells become active only on the way out - now the boss is awake.
MrStabby gave me the idea of a MacGuffin keeping the water at bay. The door to the final room could act like a plug, keeping the rest of the dungeon dry.

I would rather present tough decisions as: "Do we try to bust down the door to the treasury, knowing that we might need the time to get out". Arguments about carrying capacity and the speed of collecting loot are not that entertaining.

2015-11-26, 11:40 AM
Need a trigger? The PCs accidentally cause a breach, say a fireball in the wrong place.

Something more mundane would be an earthquake that causes the breach, but it's a bit too heavy on the railroading for it to hit at exactly the same time they get to the appropriate point - unless there's a shrine to some earth or water deity that they're looting. :smallwink:

2015-11-26, 08:28 PM
Earthquakes are not natural in DnD :smallamused:

2015-11-26, 08:56 PM
Whatever the concept that you decide on, don't forget that you should add in foreshadowing otherwise it becomes more of a "ha, gotcha" scenario with a side of "DM is looking for a TPK". They may figure out that there's some kind of water danger but hopefully not the magnitude.

Alternately, with the dungeon under a sea/lake, you could reference things like:
- water dripping down the wall
- dungeon walls adjacent to the water sometimes giving a straining, creaking sound
- water-bloated, rotting corpses in "dry" areas
They would already be aware of the water and the foreshadowing alerts them to the danger.

The boss could be the one to intentionally trigger the flooding. Realizing imminent defeat, it decides to take the adventurers with it and attacks one of the walls. An unintelligent boss could simply be something large and strong, backed up into a corner, that could be inadvertently bashing against the weak wall during the combat. Heck, some of their "misses" could promote the collapse.

If the PCs are quick, inventive, prepared and lucky enough, they can prevent the wall from eventually collapsing. They might even be able to stop the collapse before it begins. If they attempt and fail, they'll have less time to escape the crush of water and eventual flooding. Conversely, they could buttress the wall and give themselves extra time to quickly loot and escape before the eventual wall collapse. They could also decide right away to get out of Dodge.

If they've figured it out early and planned for a quick escape (via exit markings or something of the sort), then by all means give them the advantage. Unless the adventurers have been meticulous about clearing everything out behind them, have the remaining monsters also charging for the exit. It might get crowded and chaotic even if they are not directly hostile to the PCs. They want to escape too and would attack anything getting in their way. Either way, they would have to avoid more of the walls that are collapsing as they escape possibly cutting off more direct routes ahead of them. The PCs probably would not have had enough time nor supplies sitting around to buttress all of the escape route. Basically, make the environment itself the trap.

Something else I just thought of is if they decide to stop and help some of the surviving creatures or do they leave them to their fate? Would the creatures attack once they've gotten to safety, simply go their own way, or show up again in another adventure? Would they seek to return the favour at some appropriate future moment or seek to undermine the adventurers for their destruction?

2015-11-26, 09:07 PM
An earthquake is fine as long as you foreshadow it. Have an moderate earthquake be what opened up the dungeon and brought it to the party's attention in the first place. Then 1 or 2 more minor ones while they're traveling to/preparing to enter. Another minor one hits while they're in the first room, causing dust to fall from the ceiling. Make sure there's a bit of rubble from the previous quakes to show that the place isn't entieely stable. Then, when the biggest quake yet hits and starts the flooding while they're in the final room - perhaps even during the fight with the BBEG - it will seem like a natural progression rather than something the DM contrived to mess with the players.

2015-11-27, 03:54 AM

2015-11-27, 06:06 AM
Does anyone have ideas, experiences, comments to share about such kind of dungeon?

Some ideas I had:

Sinking ship: Probably too small for that "we need to stay ahead of the waterline" feeling. Also, can be avoided simply by smashing the walls and swimming to the surface.
Dungeon below the sea/a lake: Probably the most fitting location, provides a good excuse for all that water. Still, I can't think of a good trigger condition.
Repeating create water traps: as above

Here's one: The macguffin was a power/control thing, probably magical, which was also the only thing keeping the dungeon from flooding. Disturbing it necessarily means the dungeon floods. Maybe it was supposed to be a backup for floodgates that wasted away a long time ago.

And another: The PCs' enemies notice that the PCs nabbed the macguffin, and in desperation pull the plug to flood the dungeon. A particularly cunning foe might have set up traps, ambushes, or other obstacles in an effort to slow the PCs and drown them. A basic version might be reactivating some of the dungeon's traps or barricading doors on the way out. This ensures the PCs are stuck between a rock (the rising water) and a hard place (traps, enemies, obstacles).

Though since you're likely playing dnd, I'd be wary of PCs having ways to breathe water or otherwise render it a non-issue. Maybe you could put something fun in the water like sharks, piranhas, electric eels, or some ocean-dwelling fantasy creatures. Or make the water immediately toxic or acidic (maybe the dungeon was next to a sewage system or contaminated lake?). Having a dungeon flood with acid and acid-piranhas would be pretty cool. It doesn't have to mean a huge amount of damage the moment they touch the water -just enough to make it clear they can't stay in the water for too long. Besides, making the water/acid itself too immediately deadly means the party might weaponize it.

2015-11-27, 06:33 AM
Doesn't a character already have air up until 2* Con score in rounds to hold its breath under water? Secondly RAW there should be no airholes but in any sinking object (sinking not sunken as in: still in progress) there are airholes. Casters should have problems casting (as in - should be able to reach airholes in order to use spells with verbal components), mundanes have no way of attacking short of conveniently looted nonmagical spears from semiaquatic guards in the room before the final room.

Toxic or disease ridden water is another option. Disease is a penalty for being too slow while toxicity shortens the possible rounds with held breath. You might give out a freebie for one character if you feel the whole group is up the task yet one character (or player) might freak and kill his character in that situation.

2015-11-27, 07:22 AM
This is a classic variation on the "collapsing dungeon" and an awesome one at that. If your players are at all genre savvy, they should see this sort of thing coming.

One possible trigger is have the MacGuffin be the trigger; like the idol in Raiders triggers the rolling boulder, yours triggers the flood.

Alternatively, have the trigger occur slightly before they reach the end, making it a race against time not only to get out but to complete the quest!

I wouldn't put it on a RL clock though; in-game time and out-of-game time are two very different things. See combat for a perfect example where an hour out-of-game can translate to less than a minute in-game. If you want to maintain a sense of urgency for the players (rather than just the characters), constantly remind them that they're under pressure; before they're completely submerged, mention the sounds of rushing water, how the water is soaking up their legs, have corpses wash into rooms with the flood of water and so forth.

One way to regulate things and possibly create tension would be to have the flooding occur in stages. Rather than a constant flow of water, have the flood occur in predictable stages; on the hour, or every half-hour part of the dungeon is suddenly engulfed with water in a great rush; PC's and NPC's are bowled over, rushed up against walls, furniture is dashed all over the place, etc. If the PC's work out the timing, it then becomes a race to avoid the next influx of water; throw aquatic monsters in their path to hold them up.

Another idea might be to have a series of "locks" (like in a canal), which the PC's can use to slow or even reverse the rate of flooding as they make their escape. Perhaps have it so that if done in the correct order, the PC's can get out bone dry, even though some of the way out might be completely flooded at one point or another.

Kol Korran
2015-11-27, 01:57 PM
In a campaign some time ago, we played with a flooding dungeon. The place was an old sealed vault of a powerful sorcerer giant. The vault functioned as a small laboratory, but also held some valuables.

As the party explored the place, they found a few things that looked like potential traps/ encounters, but which didn't quite work- Statues of dragon heads on the walls, which didn't breath anything. Utterly shut sarcophagus, and so on... The entire vault seemed old, and somewhat in a state of disrepair. The party assumed most of these were probably flavor pieces, though they were wary.

Come the final room, it's a small chamber, with a big throne where there was a bejeweled skeleton, and some treasure, including the item the party was there for. They first thought the skeleton was giant lich, but it was but a reminder of past glory, a simple dead skeleton. (In D&D? Gasp! :smalltongue:)

But when they started looting? Well, the mechanical trap sprang, and the door shut behind them. They could hear... things... happening beyond the door. By the time the party managed to open it, some water rushed in. And the previous non functioning traps and stuff, now worked! The way I ran it:
- I had a decent size map of the dungeon, and we started counting rounds, with players playing by initiative, as if this was all one big battle, as movement was important.
- Every several rounds, I deemed the water a bit higher to force a new adjustment (Slower movement, swimming, and so on)
- Traps and some creatures (Constructs and undead) were now active, with the main purpose of stalling the party, and blocking their way. Disarming traps now proved too much time consuming.
- A few features of the dungeon changed as well, from before- A trap door no longer worked, an alchemical golem exploded, filling a corridor with sticky acid web, a trap the party new started emitting a different effect.
- The water came from a portal to... basically the plane of water (Not exactly, but doesn't matter). Worse, as a twist- the exit was allready blocked! The party had to figure out an alternative way (A secret way the giant kept in case of a misshap with the trap), and quickly!

This was quite fun, and worked well. I suggest to NOT include any hints of the flooding trap, if this is meant as a death trap (As it was in my case). The party, though about 9-10 level or so, had very little in the way of water breathing, and had to resort to other means... This was quite entertaining!

If you're interested, you can read about The initial exploration here (http://www.giantitp.com/forums/showthread.php?169769-Many-Facets-Of-Darkness-DM-s-Campaign-log-Eberron-3-5&highlight=tomer), but perhaps more importantly, about the flooding trap and escaping the dungeon here. (http://www.giantitp.com/forums/showsinglepost.php?p=12211389&postcount=104) (A small note: This was my first campaign log, and my first attempt at writing long in English. There may be some mistakes, and I really didn't use any Capping then... I'll need to fix it one day. :smallannoyed: When I'm not lazy)

Good luck!

2015-11-27, 02:52 PM
A few other details/twists?

Add currents that slow or speed movement depending on direction.

Have creatures like mummies in the dungeon, but flavour them as pickled by salt water. There is a slight clue that the whole area was flooded at one point.

Maybe a few fish skeletons underfoot.

The whole dungeon is alive - but dormant in the absence of water. Rehydration causes awakening and it can sprout tentacles etc. to grab at passing adventurers.

2015-11-27, 05:30 PM
If repeated create water is too slow, flash flood seems to be designed specifically for that

2015-11-27, 06:20 PM
I don't see why magic is needed; a few valves, pipes and a water reservoir above the dungeon such as a mountain lake would do it. It could even be deliberately triggered by guards.

A major hazard would be current; water is going to pour down stairs and getting back up will be hard. You get some of the most dangerous white water around artificial structures (such as bridge piles) as sharp angles create vortices in flowing water. Opening doors in the flooding dungeon creates flow one way or the other if the water level is uneven on opposite sides of the door.

2015-11-27, 06:55 PM
Another method for having the dungeon start filling with water is a torrential rainstorm, whether natural or created by magic.

I would probably make the dungeon only really start being difficult once the flood starts, and having less encounters on the way down into the dungeon, and encounters of lower difficulty.

2015-11-29, 08:39 AM
Lots of great ideas!

It seems like I will have to decide between two options:

The accident
The flooding is triggered naturally (earthquake/opened floodgate/MacGuffin holding the water at bay/rampaging monster weakening supports), with ample warning and foreshadowing.

The deathtrap
The flooding is purposely set up and triggered by the villain to kill the PCs. No signs of the trap until the last room.

In general, I would like to use the first scenario, because it feels more natural and less like DM-trying-to-screw-us-over. However, it has the disadvantage that the dungeon cannot be so easily tailored to provide interesting challenges. Additionally, I would have to think more about ways for the PCs to do something unexpected that would prevent the flood.

Now for some obstacles and hazards...
Regarding monsters, some aquatic/amphibious creatures should work well, as would undead, constructs and elementals. Various other creatures could be fleeing the water just like the PCs.
To ensure that some of them will be left over for the way back, I will have to trigger the flood before the PCs reach the MacGuffin, so the earthquake or floodgate option is probably best.

2015-11-29, 07:07 PM
The "accident" feels a little contrived if it is just a matter of timing. The chances of the PCs being in the dungeon just as the flood defences are breached seems unlikely.

I think that the PCs should cause the event or there is a reason why it happens as they are there (such as chasing someone in who triggers the event). Stealing the crown of Umberlee or whatever still works as a reason for nasty aquatic excrement to hit the fan.

2015-12-02, 08:45 AM
to be honest this becomes a speedissue, one seriously hindering martial characters (as some armor reduces speed) and is easily solved by the water breathing spell/polymorph et. al./healing (stabalising and healing resets the drowning sequence). As for loot, (to make sure the players don't just wait for the dungeon to completely flood using the aforementioned methods, spoilable loot.

or even funnier, make the dugeon flood, wwhich cuases some stuff to start floating and when they reach the ceiling they activate some kind of trap that collapses the dungeon unless the trap is reset (trigger at start dungeon, reset at end, fill in between with maze).

2015-12-03, 03:16 PM
Have the door to the vault water-tight with a dozen Decanters of Endless Water embedded in the ceiling. When the door is opened, the water rushes out but not enough to flood the place. They grab the loot as the vault drains, but the decanters are slowly filling up the place. Since the seal on the door is broken, they can't get the door closed again. Once the water reaches a certain point, the vault door seals again and the water is drained away.

For hints about the trap, have dried out moss inside lining the lower levels. You could also make all the wooden doors extremely warped and any metal doors extremely rusty.

2015-12-03, 04:37 PM
For less of a death trap, there is the idea of a tidal dungeon, with high tide and low tide dictating time spent in certain areas, and weather the dungeon will flood completely.

2015-12-03, 05:02 PM
The first question you need to answer is:

Is TPK a valid option?

If not, then you probably don't want to go with a visible indicator, and instead make it verbal. That way you could speed up or slow down the flow as needed.

If it is, then go with a timer or turn count or some other indicator, which will really raise the stakes.

I think placing the dungeon near a lake would work. But I'd make that lake a bit swampy and boggy if you want to add an ominous feel. As far as triggers, you could just have a room explode and expose rushing water that slowly fills the dungeon's lower levels.

If you needed to up the drama at that point, you could have the whole dungeon start to collapse, with the stereotypical "rock falls cutting off this passageway" effects. This way you have whole sections of the dungeon collapsing in on itself, which prevents the PCs from just sitting there with a waterbreathing spell and calmly trying to find a way out.

Frankly, if the magic-users have a spell that negates the challenge a bit, good on them. What's the point of having those spells if the caster doesn't get to look like a badass from time to time? Anyone who takes niche spells should be rewarded occasionally.

2015-12-03, 05:58 PM
Not so long ago I had a temple on the back of a dying giant dragon turtle filled with treasure that was about to dissapear in a maelstrom. I had this chart that based on their actions brought the dragon turtle further towards drowning. Eventually some chambers woulld flood. The temple would be turned vertical as the once mighty dragon turtle found itself helpless withing the clutches of the maelstrom. Eventually more and more water would pour in. My players escaped at the last moment with their guilds airship. The main idea was that the greedier the party got, the bigger the risk got. It was a short session I played in a public campaign and it was really awesome. You can of course expand it in anyway you want. You can make the dragon turtle as big as you want. You are DM so if you want to have a dragon turtle with a city sized temple ont its back, you only have to say the words.

2015-12-03, 06:29 PM
In my experience as a DM i learnt that you don't need to flood the dungeon: the players will do that for you!
I set up a dungeon in a caves-complex under Stormreach (Eberron): it was completely under the city except for the entrance corridor that passed under the sea. In that corridor the party was assaulted by an horde of dozens creatures. The wizard thought it would have been fun if they had been squashed by the ceiling. He then cast a heartquake-like spell (i can't recall exactly which one) and, well... the ceiling fell down and thousands of liters of water from the sea above rushed into the corridor.
Since the corridor was sloping the water went straight down to the caves flooding and killing everything!
It was nearly a TPK, also!

2015-12-03, 07:38 PM
For less of a death trap, there is the idea of a tidal dungeon, with high tide and low tide dictating time spent in certain areas, and weather the dungeon will flood completely.

This, just add a stormsurge, which the players might see coming if they take note of the weather.

You need a coastal location.

Alternatively you could take a page out of real life pot-holing where cave systems routinely flood if it rains upstairs. This would be a natural feature of Karst country. Many real world cavers have been caught out and drowned by this.

2015-12-06, 11:03 AM
Now, I cannot think of a scenario where the flooding of the dungeon both cannot be averted by good thinking, spell selection or high rolls AND it does not feel like rail-roading. (Note: I am well aware that what I describe IS railroading and at least the "dungeon starts flooding" part is supposed to be, it simply should not feel this way)

On this bit specifically, I'm thinking about something :

The dungeon is under sea (or lake) level. At the bottom, there's a big wall at the back of a long hall with columns. The water is behind the wall.

When whatever trigger you choose happens, the wall bursts and the water rushes out, knocking down the first few rows of columns. The ceiling they were supporting collapses but the water still seeps through the rubble. The consequences are :
a) Instead of rushing out and engulfing the dungeon in moments, the water steadily rises at a more manageable pace.
b) The water can't be stopped, since their are too many holes to plug and a lot are already underwater from the initial rush.
c) It is obvious that bringing down more of the ceiling won't work.

The latter point, in particular, feels much less like railroading than letting the party try and collapse the ceiling then declaring it doesn't work.

When this happens, the party could either be in the hall (away from the wall!) or in another, nearby room (the treasure room where the trigger is, maybe ?). In the former case, they'll be washed to the opposite end by the initial rush of water. In the latter case, they'll hear a very loud noise, and when they come back to the hall they'll find it flooded with a meter or two of water, half its ceiling caved in, and water flowing from the rubble.

Obviously, you'll need foreshadowing to make it work. Make sure to point out that the entrance of the dungeon is near a sea or a lake, and where ; if they pay attention to where the dungeon goes they should notice that they're under the water. Describe how the dungeon becomes more and more cold and humid as they progress. Have them pass near the wall before it goes down ; describe how it is very humid, covered in saltpeter, maybe with water spraying from minute cracks ; if they pass an appropriate skill check, or if there's a dwarf in the party, have them notice how the columns and the ceiling above are weak.