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?