Still a bit vague on the edges, but here is my take on a shifting dungeon. An example will follow tomorrow, so this could be seen as a thought experiment about dungeons.
|The basics (pic. 1)|
Maybe you'll think I'm crazy, but I wrote about this two days ago and the issue didn't let go. So when a buddy of mine was over for beer and movies, we asked ourselves what rules a shifting 3D dungeon might need. First thing we came up with: people who love mapping, will hate this. It's just not possible. Is that a problem? I don't think so. Players should not have the security of a map (at least not all the time...). All they need is a sense of direction or some tool for navigation and maybe even the feeling that a dungeon is, well, complex. Don't get me wrong, maps are nice. But they are also unsatisfying.
And what does a DM need? He'll describe it anyway, so what are the nice pictures for? What he needs is a feeling what the stone is like, are there ornaments or narrow passages. Stuff like that He needs to be able to get a feel for the place, then he can paint a picture using words. Alright, if the layout is two dimensional, it is usefull. But is it ever? Should it be? I've decided to go another way. The main dungeons in my campaign will have shifting elements.
How to sabotage and navigate
Those shifting areas have a powersource (magic or divine). The game already delivers possibilities to find such a source (scrying, some cleric spells) and research is also a viable option. A thief should be able to get there and sabotage* it so that it might not shift for some time (not destroying it, that should be very difficult and result in a very big bang). So the wizard and the thief will be busy, maybe even the cleric to some extent. Any inhabitants of or near the dungeon will keep the fighter busy, too. Dwarves might be very useful in this, but that goes without saying.
|Move those tiles! (pic. 2)|
Alright, a DM will have an idea how to describe this dungeon. This being part of a narration, it is very flexible. F**k those 10' corridors, it's about tension. The players, if they are somehow in the middle of this, might choose directions hoping the thief, the magic user, the cleric and/or the dwarf are right about the general direction. Small passages, stairs, maybe even deadends and some crushed bones are part of this.
As soon as this starts moving, a DM needs to know a few things:
Step 1: Assign range to x, y and z
The number of moving parts in every direction. This is very abstract, but that's good, because we're working with dice here. So the first step is to assign a number to x, y and z. It's the number of units a group has to move to get from one side to the other.
Step 2: Assign movement and direction
The next step is to specify how fast and where those units move. So x, y, z and the direction get a dice (see pic. 1). 1D8 for directions: 1 x, y, z = +; 2 x, y = +, z = -; 3 x, z = +, y = -; 4 y, z = +, x = -; 5 x, y, z = -; 6 x, y = -, z = +; 7 x, z = -, y = +; 4 y, z = -, x = + (see pic. 2). Another idea is to use a D10 with 9 and 10 leading to the source (9 = they can see it, 10 = leads directly there).
Step 3: Set difficulty
The last touch is to give it some features, like a pattern, safe passages, hidden rooms and a method to give them pain. This determines the difficulty of the dungeon. Big, slow moving units might get them lost, but not kill them, for instance. I'd give them a DEX-check (DEX + 1D20 with a difficulty somewhere between 20 and 45 (45 being nearly impossible and rare), everything under the difficulty would be damage (save for half, with a possibility of getting separated from the group or, worse case scenario, stuck/crushed). If there any traps (that is a unit that moves to bottomless) is as easy set as giving it coordinates. If somebody is controlling the dungeon, he might even be able to shift the group in there (if he is aware of them).
Not moving, but still complex?
If shifting is not an option, steps one and three are still good to go. Navigation is key then. They get in somewhere and they want to get out somewhere. The DM rolls x, y, z as intended, the navigators roll shifts the result in one direction. The result still gives the DM something to tell (up, down, left, right, distance). Traps and features are still fixed with coordinates.
The dungeon as enemy?
That is the gist of it. I'll do an example tomorrow to illustrate it, but for now this is enough to digest, I guess.
* Skills might be a good option, but that varies from DM to DM.