1001 One-Way Doors

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I'm in need of some one-way doors for the dungeon I'm designing - not literal doors, necessarily, but tricks to keep players from retracing their steps. In my case, I'm looking for magical effects to trap the players in a fairy-tale sort of dungeon, but in the interests of making this thread useful to as many people as possible, I invite all ideas, magical or mundane, dungeon or surface. Here's what I've got:



  • The door or passage the players entered by is simply gone.

  • The players wade through a narrow, shallow stream of water. When they return, the stream has become an Amazonian river and the far shore is not visible.

  • The players step over a narrow crack in the floor. When they return, the crack has widened into a bottomless chasm.

  • The players open a painted stone door. From the inside, the door looks identical, but it's actually just a painting of a door on a stone wall.

  • A pit trap or elevator drops the players to a lower level of the dungeon (the classic approach).

  • The door the players entered by now opens onto a solid stone wall (the unsubtle approach).

  • The players must clamber through a narrow pipe. When they return, the pipe is gushing a high pressure stream of water.

  • The party must descend a deep, sheer-sided, slippery well. When they return, someone has cut their rope.

  • The return passage seamlessly loops back into another section of the dungeon.

  • The party descend a flight of stairs. When they try to climb back up, the stairway continues infinitely, but when they turn back into the dungeon, it only takes them a few paces to reach the bottom.

  • The players are ferried deeper into the dungeon by a sinister ferryman (or an unpiloted boat). When they return, the boat is gone.

  • After the players pass a certain point, the entire layout of the dungeon level changes slightly. The new map has all the same rooms as the old one, with the exception of the exit room. The new rooms are all in slightly different positions to the old ones, just enough to seriously confuse the players.

  • The players can exit the dungeon the way they came in, and find themselves back on the surface in the area immediately surrounding the entrance. However, this is just an illusion, and no matter what way they go all roads lead back to the entrance of the dungeon.

  • The same as the above, only whatever path they follow literally turns into a dungeon corridor after a few hundred feet.


I'm not totally satisfied with any of mine; I'm hoping someone will have some cool ideas I can steal. Anyone care to share?

When they cross the threshold, they're transported 1000 years into the future (noticably or not). That's the space (or rather, time) the dungeon exists. They can try and return through the doorway, but they will only find the future version of the hallway that led to the door. The only way for the players to return to their own time is to find another way out.
Interesting ideas, but just be careful that you don't limit your players options too much.  It's great to give them something challenging to try to figure out, but if at every turn, like in your last example, everything just leads back to the same place, they may get frustrated and might not really enjoy the challenge you've prepare.  Now you know your group and this might be just the kind of thing that they like, but if you're not sure if it's something that they'll enjoy then you should talk to them out of game about what kinds of things they do like so that you incorporate those ideas.

Also, just talking to your players about what things they are interested can help give you some great ideas for what it is that you're trying to accomplish and you can be more sure that you'll have some great player buy-in since they'll have already told you that they're interested in this kind of stuff.
Thank you, but I'm fully aware of the importance of player freedom and choice. I'm not looking for ways to force the players into some preplotted adventure I've contrived for them. I'm looking for dirty tricks to impede the party's retreat from the dungeon. The basic DMing advice is appreciated but unnecessary. Tongue Out
'm not totally satisfied with any of mine; I'm hoping someone will have some cool ideas I can steal. Anyone care to share?



Why are you not satisfied?  I think you've come up with some GREAT ideas.  In fact, I'm going to steal some of yours Laughing.  thank you

 

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Are you really "entitled to your opinion"?
RedSiegfried wrote:
The cool thing is, you don't even NEED a reason to say yes.  Just stop looking for a reason to say no.
Thank you, but I'm fully aware of the importance of player freedom and choice. I'm not looking for ways to force the players into some preplotted adventure I've contrived for them. I'm looking for dirty tricks to impede the party's retreat from the dungeon. The basic DMing advice is appreciated but unnecessary. Tongue Out



I meant no offense by my statements, just wanted to put that stuff out there.

That being said, I do think your ideas are very interesting challenges for your players, and like I said before, YOU know your players and if these are the kinds of challenges that they like it already sounds like you have some awesome ideas.
@jplay: Don't worry, it's valid advice. These are just ways to block off the party's retreat; the challenge is then to find some other way out of the dungeon. Prettied-up portcullis traps, essentially.

@DaBeerds: I've got some slightly awkward requirements. It's a large dungeon, I'd prefer that there isn't single chokepoint the players have to pass through. I want something clearly magical, to clue the players in that the environment itself is working against them. It shouldn't be easily overcome by magic - my players have the fly spell, so a river or a chasm is not much of an obstacle on it's own. I'd like it to be seamless enough that the players don't realise they're cut off until they try to retrace their steps, but I'd also like there to be some sign or symbolic boundary that the players can recognise afterwards as marking the point when they passed into the otherworld. I'm too fussy, in other words.

Right now I'm leaning towards having two separate maps with different room layouts, although that might be a bit too confusing. Or maybe I can combine a couple different ideas - e.g. the party can cross the river, but the far shore is just a different part of the dungeon, or even the same shoreline.
Outside of this particular situation, I recommend judicious use of things like this. It's likely to engender failure mitigation to avoid the surprise, and feelings of being ill-used if the surprise is sprung despite precautions. If you don't want players going backwards, talk to them about it to come up with in-game reasons why they wouldn't want to go backwards. If they come up with the idea of one-way doors, then they're okay with it, but don't spring it on them.

If I have to ask the GM for it, then I don't want it.

1. The door is six inches high.  There is a fountain of dimnution that will reduce each PC to 1/12th their size for ten minutes.  The potion is rendered inert if it leaves this room.


2. 
 
 
Outside of this particular situation, I recommend judicious use of things like this. It's likely to engender failure mitigation to avoid the surprise, and feelings of being ill-used if the surprise is sprung despite precautions. If you don't want players going backwards, talk to them about it to come up with in-game reasons why they wouldn't want to go backwards. If they come up with the idea of one-way doors, then they're okay with it, but don't spring it on them.


I disagree. Obviously some of the above could be pretty unfair in other contexts - the players can reasonably expect magical shenanigans getting in and out of a fairy mound, less so the local lord's keep - but the basic principle of one-way doors, portcullis traps, sliding stairs and pits to lower levels is as old as D&D and probably my favourite kind of trap, both as a player and a DM. Rather than simply penalising the players, it heightens the tension and gives them a suite of interesting choices - where do we go now, how much do we need to conserve our resources, should we stop for treasure or make a beeline for the exit, should we try to fortify and rest inside the dungeon, etc.


For my part, I wouldn't dream of directing my player's motives the way you suggest, though of course that's a valid playstyle if it's what your players are into. For their part, my players don't need to give me permission to include a trap in my game. My recommendation is, if the players trust the DM to be fair and impartial, and the DM trusts the players to act in their own best interests, then everything will work out for the best.


@wrecan: ooh, I like the Alice in Wonderland approach. Something like that might work really well for me, actually.
I disagree. Obviously some of the above could be pretty unfair in other contexts - the players can reasonably expect magical shenanigans getting in and out of a fairy mound, less so the local lord's keep - but the basic principle of one-way doors, portcullis traps, sliding stairs and pits to lower levels is as old as D&D and probably my favourite kind of trap, both as a player and a DM.

Plenty of the old concepts in D&D have proven less than widely appealing over time, despite their nostalgia. But my post wasn't really written for you, which was why I said "outside of this particular situation."

Rather than simply penalising the players, it heightens the tension and gives them a suite of interesting choices - where do we go now, how much do we need to conserve our resources, should we stop for treasure or make a beeline for the exit, should we try to fortify and rest inside the dungeon, etc.

Those choices are not inherently interesting. A DM should be mindful of what their players will find interesting, and not be surprised if the players react less than positively to this kind of restriction.

For my part, I wouldn't dream of directing my player's motives the way you suggest, though of course that's a valid playstyle if it's what your players are into.

You won't direct them not to go backwards, but you will take away the option.

For their part, my players don't need to give me permission to include a trap in my game.

That's nice, and that's why I said "outside of this particular situation." I've seen enough posts on the forums to make it clear that it's not a good general assumption that players will have fun no matter what challenges the DM poses.

My recommendation is, if the players trust the DM to be fair and impartial, and the DM trusts the players to act in their own best interests, then everything will work out for the best.

Trust, yes, but trust that everyone wants everyone else to have an enjoyable time playing the game. Fairness and impartiality aren't enough, and are often used as excuses for unpleasantness. Players acting in their own interest seems like an odd thing to trust, and I'm not sure I follow what that implies. Is it reference to the fact that players sometimes do "stupid" things?

Trust can come and go. I can see a DM going for a long set up that requires the PCs to have several bad things happen to them by DM fiat, but if there isn't a brilliant pay-off at the end, that doesn't make the players feel ill-used, then I'd expect trust to erode.

If I have to ask the GM for it, then I don't want it.

Centauri, I don't want this thread to turn into a debate about DMing practices. Suffice it to say, your values and your assumptions aren't universally true - at the very least, not for me or any of the people I game with. If you don't like this sort of trap, then don't contribute, and let the people who do like it have their fun.
Centauri, I don't want this thread to turn into a debate about DMing practices. Suffice it to say, your values and your assumptions aren't universally true - at the very least, not for me or any of the people I game with. If you don't like this sort of trap, then don't contribute, and let the people who do like it have their fun.

Fine. All I'm saying is use things like this with caution.

If I have to ask the GM for it, then I don't want it.

The door shuts behind them, they hear the sound of grinding stone. When they try to exit through the same door they entered, they find themselves in a different room.

The room itself rotates every time the door is shut. It will not return to the same exit/entrance until "x" number of rotations have been performed.

This could have some interesting effects on splitting the party up. But should likely be a focal point for the dungeon than an annoying measure to slow them down. But ultimately can be made to work however you'd like it to. 
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Here's one:

The party has to get by some powerful creature (Dragon, Demon, etc) to get to the actual dungeon.  The said creature is asleep, bound or some such so that getting by it is no problem as long as they don't mess with it.  Once they get past it, and enter the actual dungeon, the creature awakens, gets free or so on.  Since it is too big it can't follow the party, but it would be very dangerous to go back, especially if weakened due to exploits in the dungeon.  In the case of bound creatures, a simple ward or seal prevents it from following the party, but it too will be waiting for them if they return.

Likewise, one can do this without any big bad monsters:  Simply have a case where the party escapes a castle by entering the dungeon and simply doesn't dare to go back due to the guards being on to them or for political reasons.
Ok, so I just remembered a trap that was used on my and my friends years ago that you might find interesting for what you seem to be going for.

Basically our party entered a room in a dungeon.  There were five of us.  The room was a half sphere with the flat part on the bottom.  It sloped slightly in one direction away from the entry way.

At the far end of the room, near the wall (lowest point) there was this weird little spark that went from the curved portion of the ceiling which was only about 6 feet up at this point close to the wall, directly to a small hole in the floor.  The spark would fire off about every 30 seconds and would stay sparking for a full round.

Our Kender (yes we were playing a Dragonlance campaign) decided he was going to touch the spark.  When he did he got zapped for 1 pt of damage. (not a lot considering we were all around 9th level at the time).

We continued looking around the room trying to find another passage out of it as it seemed that this was a dead end.  At that point the Kender (again) noticed something.  at the peak of the dome portion of the ceiling he saw a gem embedded in the stone.  He managed to convince one of the other PCs to give him a boost so he could "take a closer look".

While this was going on another one of the party members finally found some grooves in one of the walls that kind of looked like the outline of a Large Stone Door.

Now the Kender was close to the gem in the ceiling and using a dagger, popped it free from the stone.  When he did that two things happened.
1)  A HUGE Stone slammed down blocking the entry way that we had come through.
2) Water started shooting out of the hole that the gem had been in with the force of a fire hose.

The jet of water knocked the Kender and the PC on whose shoulders he was standing off balance slamming them to the floor.

Also, the water began pooling up at the low end of the room and steadily filling the room a little bit at a time.

Within about a minute half the floor of the room was covered in water.

Now every time that little spark went off it was hitting the water and anyone who happened to be standing in the water got hit as if by a lightning bolt.  What was worse is if you were wearing metal armor the damage was multiplied by 1.5 times.

In order to get out we had to notice (spot check....perception check for 4e) as the water continued to creep up it wasn't completely uniform.  There was a small divot in the floor that it pooled into near where the party had found the "possible" other door.  That divot was about the size of the gem the Kender had pulled from the ceiling.

Once this was figured out the party quickly took the gem from the Kender and put it in the divot.  This opened up a door in the wall that lead out from that room.

As soon as we left the room that door slammed shut and the room ended up filled all the way up with water with that spark electrifying it every 30 seconds or so.  Needless to say it was a pretty devestating trap which left most of us hurting pretty badly, and as far as we could tell there was definitely no way of going back the other direction.

Just thought I'd share that one from my past as I thought it might be something you could use in whole or part.

BTW, I was the Kender....hehehe.
Sounds like paralell universe, matrix theme meets twilight zone.  Truly epic.  I thought Matrix movie presented that very well.  Each door, any door open and reopenned, opens up to totally new location, then step in, your at new place.  Reopen that same door its still new destination..unless you have the keys from the key master, or open a particular new door.  Following matrix style to a degree probably makes it easier for players to adept right in, with added "time & space" factor, as Svendj suggested, making sense out of why a small stream is raging river and small crack is a chasm When return to same spot.  Not  only the doors take you into different "space" but also can take you different " time".  Truly epic dungeon probably created by a truly epic forgotten gods, perhaps to travel themselves between Space & Time, or as a perpectual Space Time jail for a epic villain.  Wonderous speculations Players may have.

I would use Matrix movie door idea as core skeleton and work your way out to your crazy creativity.  Best to use a setting players catch on right away so don't get too Weird and confusing, leading to analysis paralysis.  Matrix movie can provide that.  Other then that I have no clue.  Doors....Keys....Space...Time.  What a concept for a dungeon and truly epic concept of definition of what a "door" really means at a universal cosmic scale...a hinged, sliding barrier at a entrance to...Space & Time.  Cosmic Indeed.
I remember an old one-
The door to the next room is a magic mirror.
Any attempt to break or attack is magicaly reflected back and there is no lock to pick.
The answer is to take another door in the dungeon off it's hinges and place it infront of the mirror and open it causing the mirror door to reflect oppening.

Not a fair riddle really, but in a fairy tale dungeon as you described something could tell them this is a riddle and give them a clue as to what to do. of course if they forget to take the off it's hinges door with them there is no real way to get back out.


Being chased by something big a scarry the PCs must colapse a tunnle or disspell a magic gate behind themselves so "it" won't follow them.

The sea looks at the stabillity of the mountian and sighs. The mountian watches the freedom of the sea and cries.
I guess my question would be, why would the party want to retreat? Are you anticipating situations where they would want to go back? Part of your design might focus on mitigating those kinds of situations and instead presenting overwhelming benefits to continuing forward.

I wish I could be more specific, but I'm not having many ideas right now. I'm trying to say if forward looks really good they won't be thinking of going backwards, rather than the situation saying "you can't go back."
Centauri, I don't want this thread to turn into a debate about DMing practices. Suffice it to say, your values and your assumptions aren't universally true - at the very least, not for me or any of the people I game with. If you don't like this sort of trap, then don't contribute, and let the people who do like it have their fun.

Fine. All I'm saying is use things like this with caution.




And the general concensus seems to be that people don't need your forewarnings and grim portents. Next time, why not simply try answering the OPs question instead of trying to dissuade him from something that is entirely harmless?

Now, of course you weren't refering to him specifically after all because you put "Other than in this situation" but you still felt the need to post the post...which really just seems like a way to cover ones tracks rather than directly stating something. "Oh I'm not saying your a bad DM, just that bad DMs often do what you're doing." Uh huh.

I'm on a journey of enlightenment, learning and self-improvement. A journey towards mastery. A journey that will never end. If you challenge me, prepare to be challenged. If you have something to offer as a fellow student, I will accept it. If you call yourself a master, prepare to be humbled. If you seek me, look to the path. I will be traveling it.

 

Proudly playing in many wrong ways. I'm not afraid of playing wrong according to the rules. Why are you?

 

100 Crack Reply of the Yagamifire. You are already wrong.

If you want a vicious door (something that just seems really mean) you can have a hall that works like an spike-angle trap. In effect, going one way down it is fine...but going the other way one encounters angled spikes facing them. In a magical scenario this can be achieved with one-way force effects...which makes for a really creepy description in that if you move backwards against them they start to press then cut.

I'm on a journey of enlightenment, learning and self-improvement. A journey towards mastery. A journey that will never end. If you challenge me, prepare to be challenged. If you have something to offer as a fellow student, I will accept it. If you call yourself a master, prepare to be humbled. If you seek me, look to the path. I will be traveling it.

 

Proudly playing in many wrong ways. I'm not afraid of playing wrong according to the rules. Why are you?

 

100 Crack Reply of the Yagamifire. You are already wrong.

I like that idea Yagami.  That's a good one for what the OP is looking for I think.

Here's another that I thought of.  It's kind of simple and won't work if the party has the ability to fly or climb walls like a spider, but if that's not an issue this one might work.

Basically have an impossibly deep chasm that is like 500 feet across.  It is spanned by a very old and rickety rope bridge.  The walls of the cavern that this chasm is in (and the cliff walls of the chasm itself) are covered in a slippery, slimy substance making it near impossible to just climb around on the walls.

Now when/if the party decides to cross the bridge, once they get about halfway across some enemies (whatever type you want) attack them from the way they just came.  Now here's the risky part.  You would really like to see the bridge destroyed to prevent the PCs from retracing their steps.  Here's a couple possibilities to assist in that.

1) During the fighting, one of the enemy cuts the rope(s) for the bridge causing it to fall apart.  Danger here is that some or all of the PCs may not make it to the other side in time and end up falling to their doom.
2) PCs decide to quickly run to the other side and cut the rope(s) themselves causing their attackers to fall to their doom.  Would be ideal because then the PCs have created the non-return situation themselves, and at the same time they thought of a clever way to defeat their attackers.
3) Have one or more of the attackers fire flaming arrows at the party.  Any arrows that miss end up hitting the bridge and lighting it on fire.  This has the benefit of giving the PCs some time to get across to safety before the rope(s) burn all the way through and destroy the bridge.

There are lots of other ways that this could go down too where the bridge ends up destroyed, and of course there's always the possibility that the PCs find a way to save the bridge thus ruining the original plan of not having a return path.  So in my opinion it would be really cool, and Ideal if the second thing I described happened.

Of course as a last resort, if the PCs were retracing their steps and came back to this chasm you could just say that the bridge was destroyed by someone/something after they had crossed it and moved further into the dungeon.

Anyway, just an idea, let me know what you think.
Thanks for the ideas so far. Not all of these fit the fairy-tale vibe I'm planning for this dungeon, but as I've said I like this sort of trap in general, so it's all grist for the mill. (jplay, encouraging the players to cut off their own escape is particularly elegant, though it probably won't fit this specific situation).

I guess my question would be, why would the party want to retreat? Are you anticipating situations where they would want to go back? Part of your design might focus on mitigating those kinds of situations and instead presenting overwhelming benefits to continuing forward.

I wish I could be more specific, but I'm not having many ideas right now. I'm trying to say if forward looks really good they won't be thinking of going backwards, rather than the situation saying "you can't go back."


I think you've misunderstood what I have in mind. There are lots of reasons the players might want to retreat - the most common being that they're running low on HP and spells and don't want to risk resting in the dungeon. I've got no problem with that. Even though I use one-way traps pretty frequently, my dungeons are non-linear enough that the players can nearly always find their way back eventually - the trap just means an added complication if the players happen to trigger it.

In this specific case, I think that being trapped in a fairy tale dungeon will be quite a fun situation to play, and I'm building the dungeon accordingly. Think of the dungeon as one big trap. The players might not enter it at all - if they're cautious and they investigate the place first, find out it's a fairy mound, hear the rumours about people disappearing never to be seen again, etc, they might decide it's not worth the risk and go adventure someplace else. Or they might charge right in, or accept the risk and proceed anyway. In that case, the consequence is that they'll end up trapped inside and are forced to find another way out (something I think will be an enjoyable challenge). I'm setting the trap and baiting the lure, but it's up to the players to decide whether to take the bait. If they're not interested I'm not going to try to persuade them.

I hope that clears things up a bit.
For fairy tale type one way doors and schemes to get the party to go only one way you might want to check out the classic movie Labyrinth. There are several very good fairy tale type one way doors/paths in that movie.

The other is a tried and true classic:  The one way Mirror-gate.  The party goes through and there is simply no way back through the mirror since no hole or gate is there forcing them to find another way.  It doesn't get much more fairy tale than that, short of a witch casting the players to another realm/place which would work too.
If you're thinking fairy mound, then the tricksy-er the better. Also, anything disorienting or illusion based is a safe bet.

Perhaps instead of changing the layout of the dungeon you could have several paralell dimensions of the same layout, where nearly everything is identicle save for inhabitants or key differences. For example let's say the pc's kill a monster to gain passage into the door beyond it, only to find that the room they've just fought to enter is a dead end. The doorway unknowingly transports them into a paralell version of the dungeon they're in, so when they come back out the body of the monster and the original exit are gone, but everything else seems exactly the same. Maybe there's another door leading in a different direction instead. Sprinkle 3 or 4 versions of this all on top of one another with a non-obvious method of changing which dimension the pc's are in and a 10 room dungeon becomes a labryinth hundreds of adventurers could previously have become hopelessly lost in.

Other ideas for one way doors:

-a fountain of viscous liquid in a room with a constantly burning unnatural fire blocking the door, the pc's can coat themselves by bathing in the fountain which will protect them from being incinerated by the flames, but the protection burns away the substance (and any further protection) as they pass through

-a pool of water with some sort of treasure at the bottom(or better yet an illusion of one), but anyone who dives in and resurfaces is in a different room.

-a doorway so overgrown with plants that the only way to get through is to cut/burn/whatever a way through. The kicker is once thru tha plants grow back and adapt in such a way that duplicating the actions will have no effect (i.e. if the pc's cut their way through the first time slashing weapons will have no effect as the vines grow back harder than steel, then if they burn their way through the vines grow back harder than steel and fire resistant). This doesn't totally cut off a retreat but forces players get more and more creative while asking themselves "is it really worth it to go through this door again?" for fear of eventually being trapped on one side of it. 
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