For a basic dungeon adventure, draw the dungeon floor plan on graph paper, number the rooms (or other important locations), and then write yourself a “key” to remind yourself what monsters, treasures, traps, and tricks are found in these numbered locations. The traditional dungeon, which many people on the internet call a “megadungeon” is a vast labyrinth of underground tunnels, rooms, corridors, and chambers, extending many levels down beneath the surface. It might contain subterranean lakes, rivers, chasms, and cave-ins, and it is certain to contain traps for the unwary, monsters in their multitudes, and most importantly: treasure beyond the wildest dreams of the players—if they can bring it out safely.
In designing a megadungeon, it’s often helpful to start with a quick cross-sectional map of what the dungeon looks like. But the real meat of designing the dungeon comes when you start making the floor plans of the dungeon levels themselves. An example floor plan is shown here, together with a key for the first few rooms on the following pages. This should give you a basic idea of how to start designing your dungeon.
- Entry Room: A double line of pillars runs from north to south in this room, and there is a massive statue at the southern end of the room, a fat creature with a horned head holding a massive bowl in which fires burn mysteriously without any visible source of fuel. A corridor leads to the north, and there is a door in the East and West wall. No monsters. The fire pit can be used to light torches.
- Giant Ant Room: This room is the home of a nest of giant ants, and the stone floor is broken up and uneven from their burrowing. At any given time there will be 1d4 giant ants in the room, and there’s a 10% chance one of them is a warrior ant. Checking around on the floor will often reveal some sort of treasure the ants have churned up from their nest (from past victims, most likely). Roll 1d6: 1–3 = no treasure; 4–5 = 1d10 gp; 6 = 3d6 gp.
- Empty Room: the only thing in the room is a broken helmet (useless and worthless). The ceiling of the room is damp, and drips.
- Empty Room: Note that there’s a secret door in the south wall. Roll 1d6 for each character to notice the door if there is a cursory inspection of the walls; humans, Elves, and Halflings have a 1 in 6 chance, and Dwarves have a 2 in 6 chance to notice. If the characters take time to search, using up one minute per 10 ft section of wall, they may roll again with the same odds.
- Goblin Room: 8 goblins make their lair here. They have treasure of 200 gp.
- Stairs Down: This room is empty, but the wind drafts create a strange whistling noise.
- false door
- portcullis or bars
- double doo
- revolving door
- secret door
- concealed door
- archway or window
- floor trap door
- ceiling trap door
- cave wall
- one way door
- one-way secret door
- depression trap or teleport
- fountain well
- cave-in stalagmites
- chair or throne
- fire pit
- slope up
- slope down table, chest, all kinds of other things
- water or pool
- pit trap, covered
- pit, open
- sliding stairs
- crawlway (the narrow passage) gas
- crank or machine
- elevated area (balcony or ridge) dotted line is a passage crossing underneath or over another
- curtain bed
- dais or low platform
- stairs down stairs up
- circular staircase
Listening at Doors: Listening at a door has a 1 in 6 chance of success for humans; non-human characters most likely have better hearing than humans and can hear noises with a 2 in 6 chance of success.
Opening doors: Stuck doors (and many doors in an ancient dungeon may be stuck closed) have only a 2 in 6 chance of opening on the first try. Smashing through a door with (up to 3) characters gives each character a normal chance of success, but they will spill into the room and should automatically lose initiative if there are monsters within.
Secret Doors: Secret doors are not spotted by chance while passing by; they must be searched for. Searching for a secret door takes a turn (10 minutes of game time) for a 10 ft segment of wall. Humans, Halflings, and Dwarves have a 2 in 6 chance to find a secret door while searching, and Elves have a 4 in 6 chance.
Traps and Pits: Anyone passing over or through the trigger for a trap has a 2 in 6 chance to spring the trap. It is suggested (but not required) that for traps involving a stone trigger (such as a pressure plate) or a hole or gap in stonework (such as a falling block or an arrow-hole), that a dwarf has a 1 in 6 chance to notice the features of a trap before passing over/through it, as long as he is moving at a careful speed; and that he has a 3 in 6 chance to notice features of a trap when he is searching (one turn per ten-foot square of wall or floor). Identifying the features of a trap does not tell the dwarf how to disarm the trap (although in some cases the disarming mechanism might be obvious once the trap’s visible features are identified).