An entire adventure can be played out in one single tunnel. The adventure can be recorded in measures of time, not space. But dungeons, by the flat thinking of the level-driven two-dimensional design, tend to strictly obey an ad hoc limitation: one room, one encounter.
This logic is perpetrated by the pre-designed formula, which is unjustly narrow in order to address the abilities of every DM who chances to play the dungeon. In other words, the successful dungeon must be designed for the lowest common denominator: the noobie. And noobies have enough on their plates without having to juggle various events occurring simultaneously.
You can assign certain events to occur after such and such a period of time has passed since the players enter the dungeon ... but you can't be certain they'll be in the right place at the right time to witness the event and make sense of it. You have to assign the event to occur when the players pass a certain point, or you risk ruining the value of the event. If an explosion happens and the players are in the wrong part of the dungeon to hear it and thus react to it, the explosion is wasted. Trees fall in the forest all the time, but a still, dead tree makes for dull filming. Being there for the fall is better.
Having this situation in mind for the first level of the dungeon I posted some weeks ago, I find I have to add the same dungeon level over again. What happens, to remind the gentle reader, is that the party enters the 'dungeon' on some pretext following an invasion by an unknown force. The force moves ahead of the party, kills whats in the tunnels and the party finds themselves following along and picking up clues.
Now, once the party is deep enough inside the dungeon that they can't easily get out, a new group is introduced. These are 'shock troops', who have been called by the denizens of the dungeon to come in and clean up the disaster. The shock troops, and the people who called them, don't know anything about the party's presence ... and naturally the shock troops aren't interested in asking questions. The underground facility (for that is what it is) has been invaded, and the party is in the middle.
The premise I would use would be to have those survivors right outside the entrance to the facility presume that the party are the shock troops. This could be done by having the outsiders seriously wounded, groggy and willing to assume anything in armor must be help. The party, not knowing they are being mistaken for a crack troop of regulars, blindly enter the trap and get caught there.
The image below (which can be found, as ever, in full size on the wiki - below the original first level image) only shows details important to the entrance of the shock troops. Gaps in logic or circumstances must be filled in by the DM, as it's impossible to account for all the possible activities and distributions of the party. Suffice to say, when the yellow hex on the map is crossed, the shock troops come through the door, and wherever the party is, that's where the party is.
|The First Level once again, with new things happening|
If some of the party are in the cloak room when the yellow hex is crossed, I'm sure the DM can figure out that the shock troops enter the picture from a little further up the tunnel, from the front entrance of the cloak room and so on.
I have already received word from one DM who is running his players through this dungeon, and his players are having a great old time - shock troops and all. So I hope others can get some fun out of this.