There have been a lot of cool dungeons there over the years, check it out. Anyway.
There's a game called Five Nights at Freddy's that has you working a nightshift at a food joint and trying not to get eaten by haunted animatronic death robots. The fandom is huge and rabid so I decided to watch a let's play to see what all the fuss was about, and then the principles of that game struck me as a potential source of fuel for a dungeon of OSR problem solving a year or two later. Managing a limited amount of time and needing to be in two places at once, and having the best defense against monsters be not swords, but doors. But doors that you can't just cower behind forever. Anyway, I made an attempt at this dungeon a while back in the BFRPG campaign and it went fairly well.
The players read the journal left behind, made a plan to patrol the place and assign people to various jobs and lookouts, and all in all did a good job of keeping the candles lit. I had 7 'tiers' of difficulty that made certain enemies 'wake up' and move faster, but the players ended up betraying the demonic host of this place, and while no casualties ensued, they did get teleported to the undersea and I realized having a demon as the source loot was a bad idea, because seriously who would trust a demon. Also, the way the doors worked, it was a bit to easy to simply make a few contingency plans and otherwise stay holed up behind 'em, which made it less of a real time roleplaying challenge with decisions to be made moment to moment and more of a static puzzle solvable from the get-go.
Still, the players found it memorable and mentioned that it was 'stressful' which was the feeling I was aiming for, so I think it was mostly a success. But it could be better! Faster! Submitted to the one page dungeon contest!
First off, the demonic patron of the place is replaced by 'The Device.' The reward of this place is supposed to be reliable and not another source of uncertainty and anxiety. A huge 'we did it' and sigh of relief to make up for the hectic multitasking required to get here.
Secondly, I changed how the doors worked. They're still slow to open, but they have imperfect coverage. Blocking the monsters from coming one way will set them to wandering elsewhere, and they'll eventually find another way in if you don't react to the changing situation. I think this is the most important change besides the candles.
In the original challenge, the reward scaled per number of candles lit. In this one, you have to keep them all lit for at least 10 minutes. This is to set the players running routes of their own rather than huddling in the safest spot and occasionally relighting candles and doing other things. Not many monsters will actually try to extinguish candles, but the core ones that do, the shadow reflections, are best dealt with by getting somebody else to take it down. The trick is that that person will possibly end up spawning a doppelganger themselves unless they try to kill/reach it with no light source, in which case grues will be a problem.
This dungeon actually encourages players splitting up to get more done. Fortunately, players will generally establish checkups on each other in a situation like this and the place is pretty small so when things go bad and get hectic, they'll usually bump into each other as they rush around, especially at slow to open doors.
I guess I can talk about everything in more detail as advice for anyone who might run this place.
'RUNNING DISTILL THE BLACKEST GOLD'
First off, the players should be well-informed if they're low level. I'd honestly probably just give them the entire one-page dungeon as the 'adventurer's journal' they find in 7. The rude surprises in this dungeon come from opening a door and finding a monster behind it, or running a patrol route and finding Dave isn't pushing down the water dragon head like he should be. The surprise shouldn't be 'haha this weird ass monster you knew nothing about killed you.' Even the 'bonus monsters' were designed to create specific problems for the players to ponder how to overcome.
Another important thing to remember is time. I assume 1 round of combat = 10 seconds so that if you need to open a door, it's 3 rounds of monsters eating your face if they're already on top of you. Depending on what system you use, you may want to alter door-opening speeds, hallway traversing speeds, and how wakeful the water dragon is.
Also important to remember- there are not wandering monsters. You'll need to keep track of where the players and monsters are on a minute-to-minute basis at least. Don't think of it as tedium, think of it as training for timekeeping! Also if you don't fairly and accurately track the monster movements it makes all this kinda pointless.
One-The Device
The treasure from this thing should be good, aite? Like, if someone solos this place, there should be enough gold for them to level up, easy. This place can be stressful and require a lot more thought to survive so it needs to be worth it. My players really liked the idea of 'fusing' different magic items together, so giving that ability to the Device can be a great way to condense hoards of magical items into unique items, or grant unique abilities to people (though they'd have to stay by the device while it operated on them...).
The Narrow Hall- The design goal here is a shortcut, but a dangerous one. It allows you to skip certain doors and hallways, but really play up the whole 'if a monster catches you while you're squeezing through here you're screwed.' if the Bride is seen (and therefore petrified) in here, she'll need someone on either side to push/pull her out. Or like, someone with giant strength. This dungeon is mostly aimed at low level people who aren't gonna just magic their way through walls or anything.
Two-Tree Altar
This room is pretty simple. It's a dead end or an important route depending on the C door configuration, Also it has a giant tree you could climb if you get cornered. Also, an altar to keep an eye on. Said giant tree also has one of the extra perils sealed inside if the players seek to up their game.
Three- Flooded Room
This is sorta meant to be the spooky basement room. You need to get there to light the altar. But you can't get there without spawning a shadow reflection of yourself and everyone with you... unless you go there in darkness, but that means you won't be able to see Father Darkness coming if he's nearby, and of course grues may be an issue. In the event you go there and get cornered by Father Darkness, you can dive into the water so he can't sense your breathing, at the expense of your torches. You can turn this room into a giant underground lake and have a boat bring the players here and it shouldn't affect the dungeons 'flow.' Normally I'm all for alternate entrances and exits, but this one can be hard to tinker with without throwing off the implications of the layout.
Four- Bride's Room
If you want to throw a surprise at the player, having the bride's abilities be initially unknown is a good option. This is a fairly ignorable room, honestly, but players may very reasonably think 'let's just set a watcher here to keep an eye on her and prevent her from running around.' This won't work, but will make for a good moment when Father Darkness shows up, she scampers off under the cover of his darkness, and the player runs off to tell people that everything's gone wrong.
Flooded Hall-
This initially was way more complicated, but now it's just a hallway divided by a deep trench of water into 2 sides and a rib bridge in the middle. Plus spooky giant bones. In any case, this hallway is just to make more interesting encounters with the monsters due to the separated paths- ranged combat across the watery trench, a battle on the bridge, various stealthy options. It's overall just a more dynamic place than the other halls.
Five- Door Nexus
While the most secure place to hole up is probably the device room, five also gives good control of the movement of monsters via door manipulation, and is near several altars and the water dragon head. Five is also a deathtrap. If a monster DOES make it in, your exits are either a slow door, or a variety of dangerous hallways.
The Winding Hall
Traversing it takes 1d3 minutes. In terms of speed, it is always inferior compared to other hallways, and can lead to strange shenanigans like a monster pursuing you inside and arriving at the destination before you do. This is a gamble and a way for players to delay and bamboozle monsters by careful use of the B door.
Six- Water Dragon Room
You can't get here without braving either a shadow reflection or going without light, and the need to constantly push it down or check if it needs pushing down is an important 'loop' of gameplay in this dungeon. Apart from the two levels of elevation that might be able to be turned against monsters and players, this is either a relatively peaceful room or a high traffic route depending on door configuration.
Seven- Blackened Gold Room
The final candle altar is probably also the lowest-traffic room. Enemies and players alike have little reason to choose this route, which may make it a haven for skulking grues. It has the 'adventuring journal' here because it is a likely first room to enter, assuming you use the suggested chain entry, so if you change up how to enter this place I'd suggest also changing the journal location.
Grues The Room
Less of a real room and more an excuse to have an entrance/exit/shortcut to unspeakable depths of your megadungeon. Also, a lightsource left here to keep the Grues from entering will need to be checked on every so often. If the players throw the golden bride down this pit, they should get a good amount of time free of her, but when she returns (2d10 minutes, probably), she'll have a horde of grues with her and will extinguish any light left here to allow them entrance.
The Golden Bride- Though relatively feeble, she is an immortal being who wishes to keep her immortality by chugging gold from the device and due to becoming an inanimate statue if anyone sees her, she literally can only be herself among blind grues and father darkness and so on. Her intended complications are opening doors the players don't want opened, and standing in doors to prevent them from closing. Also she can block the narrow hallway. Chopping her up and other attempts to debilitate her are doomed to fail due to her immortality resetting her to impeccable form whenever she changes forms between unseen flesh human to seen inanimate gold statue. If she makes it into 1, she'll gobble molten gold at a rate of -10% final reward per minute (or like, -10% power if the device is fusing magic items or something), Though on the personal level she's nuisance not threat and she won't bother the altar candles, she'll open doors for Father Darkness and extinguish light sources to sic grues on people and I'd be shocked if the players don't try to find more permanent ways of dealing with her than just keeping an eye on her to keep her statueified.
Father Darkness- It doesn't really matter what Father Darkness actually is so long as he's dangerous enough the party doesn't want to fight him, is shrouded in darkness and so indifferent to light, and can't open doors. I went with an exotic Jiang Shi vampire for a few reasons.
1- You can hide from them by being quiet and holding your breath, allowing low level players a chance
2- Vampiric immortality makes him hard to deal with permanently even for parties that might be able to 'kill' him
3- Level drain is scary to everyone
Father Darkness is THE monster of this place. The door system is designed to keep him at bay, and the layout of the place designed to flee from him until you can get a door between him and you. Getting cornered=death. But note that the darkness blinds him too, so if he catches a player he should be attacking with penalties for being blind, so they should have at least some time before their chi gets sucked out their eyeballs.
Grues- Grues are not all that relevant unless the players start sneaking around in darkness.If you have a light source, you are 100% safe from grues (though they can follow uncomfortably close if you have a candle). If you have no lightsource, you'll probably get eaten. The point of grues is to add an extra 'thing' to check on (a lantern set at the grue shaft, probably) and to make water hazardous, since if you take a dip you'll lose your light source. This assumes the players don't have some bullshit eternal flameless light like Continual light of course. If they do you may as well just take out the grues.
Shadow Reflections-
These are sort of a 'movement tax' to certain locations. I'd recommend them emerging 1d6 minutes after a player passes the shadow mirrors, then going to hunt down the original and extinguish candles they happen across. As they can only attack the original, it's best to have one person pass the mirrors, then kill the duplicate with someone else. If they get out of hand, you can have other monsters target them for destruction, but if you feel they're not enough of a threat, you can add in doppelganger problems like them being indistinguishable from the original, with their memories but a twisted goal, etc etc. You can also make them extremely weak to other players targeting them- like, goblin weak.
You can also shift the shadow hallways around, or add a third one. They're meant to be enough of a threat that players will sometimes prefer to risk going lightless (and being eaten by a grue) but not so much of a pain that they become the main focus. So don't be afraid to tweak how these work in different cycles.
Golden Seals and Extra Perils
This is a way to add replayability to the dungeon and allow the players to get greedy and bite off more than they can chew. I think my extra perils are well designed with the dungeon in mind, but you could add anything so long as it complicates the basic gameplay loops of the place and isn't just some random killable monster. Also, I'd probably limit the device to only working once and then requiring the seals to be unlocked for 1 extra use of the device per unlocking, lest very clever or powerful characters acquire a low-risk source of infinite wealth.
The Nurikabe- Blocking off a hallway or door with a sudden wall can change things up ridiculously. The Nurikabe should move to other locations after it successfully blocks someone for, say, 1d6 minutes, because it staying in one place forever would be either ignorable or totally scenario-ruining.
Sneaking Slime- This monster can ooze through doors, and breaking rules like that should be spooky to players who have come to rely on the doors.It paralyzes people, extinguishes their light, and leaves them to other monsters. Paralysis shouldn't last long- 1d6 minutes, maybe, so there should be a chance of rescue if someone falls victim to it. It might extinguish altar candles if that's where a player got paralyzed, but shouldn't do so immediately. It should also be extremely slow- a threat only if you stay in the same room as itor get ambushed.
Methane Elemental- Another monster designed to complicate the use of open flame. While the detonations cause damage, the huge noise attracts monsters that aren't already chasing someone. The idea behind this is to make players choose to take a different path when they smell it, douse their torches and risk advancing through it blind, or detonating it intentionally to lure other monsters to that location. Again, if the players have Continual Light pebbles or something, you shouldn't bother with this one.
Hot Dog- A playful dog made of lava. Injects some levity and requires fast thinking on how to distract the creature without angering it. Gets interesting if the Methane Elemental is about, or if you're trying to sneak around in the darkness. Maybe if you're nice enough it'll become your pet!
