Decide on the basic form and structure of the dungeon (the table below gives some examples) and begin to consider ideas for the main rooms or areas.

Based on the selected adventure scenario and dungeon setting, decide what types of monsters inhabit the dungeon, choosing from the monsters in this or other books, creating new monsters specially for the dungeon, or tailoring standard monsters to the location.

Overall shape: The structure of rooms and connecting passages will be determined by the dungeon setting (e.g. rough cavern walls, carefully laid-out defensive structures, etc.).
Mapping scale: Typically, dungeon maps are drawn on graph paper with a scale of 10′ per square. (Larger or smaller scales may be used as appropriate.)
Numbering: Give each area (e.g. room or cave) of the dungeon a number, so that the area on the map can be easily cross-referenced with the description of its contents (see step 4).

Make notes, as follows, describing each numbered area on the map. This is called stocking the dungeon.
Important details: Monsters (including the possibility of patrols in the area), traps, tricks, treasures, or special magical effects that are present.
Secondary details: Additional descriptive details such as furnishings, everyday items, smells, sounds, lights, etc.

First stock areas containing anything that plays an important role in the adventure—the main monsters’ lairs, special treasures PCs have heard rumour of, NPCs involved in the adventure scenario, etc. After detailing the most significant areas, stock less important areas, using the random room stocking procedure if desired.

Monsters should normally be placed on the dungeon level equal to their HD (e.g. 2 HD monsters on the second level). When placing monsters of different HD, it is recommended they not be more than 2 HD higher or lower than the dungeon level. Monsters placed on levels below their HD should appear in reduced numbers, and those on levels above their HD should appear in greater numbers. Monsters with several special abilities may be treated as 1 HD higher for this purpose.

Treasure is usually guarded by monsters or traps, but sometimes an unguarded cache of loot may be found.
Experienced players: When designing dungeons for experienced players, the referee should consider placing only very few completely unguarded treasures.
Deep dungeon levels: The referee may wish to not place any unguarded treasures in the 9th or deeper dungeon levels.

Monsters: May be selected by hand or rolled on an encounter table.
Specials: Weird or magical features of an area, including tricks or puzzles.
Traps: If treasure is present, the trap may be set so that it is triggered when the treasure is tampered with (a treasure trap). Otherwise, the trap may be triggered by simply entering the room or a certain area of it (a room trap).
Treasure: If a monster is in the room, roll the treasure type indicated in its description. Otherwise, the treasure depends on the dungeon level (see right).

1. Falling block: Inflicts 1d10 damage (save versus petrify to avoid).
2. Gas: Poisonous gas fills the room (save versus poison or die).
3. Mist: Harmless; looks like poison gas.
4. Pit: Opens up beneath characters’ feet, inflicting falling damage on any who fall in (see Falling).
5. Scything blade: Swings from the ceiling, attacking for 1d8 damage.
6. Slide: Opens up beneath characters’ feet, sending them to a lower level.

1. Darts: 1d6 spring-loaded darts fire at the character, doing 1d4 damage each.
2. Flash of light: Causes blindness for 1d8 turns (save versus spells).
3. Hidden monster: e.g. a Snake. Released when the treasure is disturbed.
4. Illusion: Typically of a monster. The monster has AC 9 [10] and vanishes if hit in combat. Its attacks do not inflict real damage: a PC who appears to die just falls unconscious for 1d4 turns.
5. Spray: A mysterious liquid covers the character. Monsters are attracted to the smell: the chance of wandering monsters is doubled for 1d6 hours.
6. Sprung needle: A needle coated with poison jabs out (save vs poison or die).

1. Alarms: Entry alarm that attracts nearby guardians.
2. Animating objects: Inanimate objects that attack if disturbed.
3. Falling blocks: Stone block falls to prevent passage.
4. Illusions: Illusionary passages, doors, or stairways.
5. Shifting architecture: Doors lock and the room rotates, rises, or falls.
6. Strange waters: Pool or fountain with weird, magical effects.
7. Teleports: Magical portal or teleporter to another area of the dungeon.
8. Trapdoors: Leading to a hidden area.
9. Voices: Walls or architectural features speak or moan (e.g. a talking statue).

See Treasure Types for details on the treasure listing format used below.
Level 1: 1d6 × 100sp; 50%: 1d6 × 10gp; 5%: 1d6 gems; 2%: 1d6 pieces of jewellery; 2%: 1 magic item.
Level 2–3: 1d12 × 100sp; 50%: 1d6 × 100gp; 10%: 1d6 gems; 5%: 1d6 pieces of jewellery; 8%: 1 magic item.
Level 4–5: 1d6 × 1,000sp; 1d6 × 200gp; 20%: 1d6 gems; 10%: 1d6 pieces of jewellery; 10%: 1 magic item.
Level 6–7: 1d6 × 2,000sp; 1d6 × 500gp; 30%: 1d6 gems; 15%: 1d6 pieces of jewellery; 15%: 1 magic item.
Level 8–9: 1d6 × 5,000sp; 1d6 × 1,000gp; 40%: 1d12 gems; 20%: 1d12 pieces of jewellery; 20%: 1 magic item.