I am keying the dungeon in two passes. First pass, I go through the map and mark each room as X (trap), M (monster), T (treasure), S (special), or a combination of those. As I do that for each room, I write a one-liner describing what should go there. Most of the rooms are pretty easy to populate, but after a while my brain goes numb, and I just write "special here, figure out later".
During the second pass, I'm going through each room and expanding the description to more clearly state what I was thinking (it's very easy for me to forget details in the middle of a session), and to come up with ideas for those "figure out later" areas.
This particular pair of rooms was a "T" and an "M". The "T" got this one-liner: "Net trap, rings bells when triggered, morlocks in room 137 attack." I thought it was pretty lame while I was writing it down, but after fleshing it out a bit, this could easily be a TPK (total party kill, for those not familiar with the acronym). Players beware...
136. Present from the Morlocks
The floor of this room is covered with debris (stone, wood, and bits of dried fungus). The far southern wall is covered with some kind of fungus, running from floor to ceiling.
Suspended from the ceiling is a large net of leather, dyed gray like the stone ceiling above. It has several bits of rusty metal tied to it.
There is a tripwire buried under carefully placed bits of loose debris in the center of the room. It runs down to the southern wall and up, under the fungus, to the net. If tripped by a player crossing the room, or poking around in the debris with a pole, the net will drop, trapping all players in the northern 30’ by 30’ section of the room. A save vs. paralyzation will allow players who are near the exits or southern end of the room to escape the net. Other players are automatically caught.
The metal tied to the nets will make quite a racket as it falls, alerting the morlocks in room 137, who will come to see if they have captured the delicious goblin-flesh they have been hunting for. They aren’t averse to a bit of human, of course. It will take one round for the morlocks to arrive.
It will take 8 points of damage from an edged weapon to cut a player free from the net (no roll to hit needed). Each player caught will need to be freed individually. A player caught in the net may try to cut himself free, but cannot effectively attack or defend against the morlocks (and will thus have no Dexterity bonus to AC while trapped).
If players explicitly look at the ceiling, they will see the net. Otherwise, they have only a 1 in 6 chance (roll once for the entire party). The tripwire running up the southern wall has been deliberately buried under fungus placed here by the morlocks, and is not normally detectable.
137. Morlock Hunting Party
6 morlocks (AC 8, HD 1, hp 5 each, #AT 1, D 1-6, MV (40’), Save F1, ML 9) are here, waiting for the trap in room 136 to be triggered.