Building A Dungeon

A “dungeon” is any place where monsters and treasures may be found. A dungeon is usually a group of rooms, connected by corridors. It could be a castle (new or ruined), some caves, or anything else you can imagine.

The “level” of a dungeon is a number that identifies part of the dungeon, and usually indicates the amount of danger present in that area of the dungeon. Level One, or the “first level,” is usually the place where the smallest monsters and treasures can be found. Level 2 is usually more dangerous than level 1, and as the numbers increase, so does the danger. A dungeon may have any number of levels.

A good dungeon is reasonable. Its design is carefully thought out, and the monsters and treasures are placed for a reason. Even a random dungeon layout could be a good dungeon if the monsters within it were selected and placed carefully. For example, randomly drawn caves would give a disorganized design of rooms and corridors, but could be a good dungeon if occupied only by cave dwellers, such as animals (normal and giant) and human-like monster tribes (such as goblins).

Draw the Map

Using graph paper and pencil, draw a map of the dungeon. First, select a scale. The scale of a map is the number of feet (length and area) represented by one square on the paper. A common scale is “1 square = 5’ x 5’ area.” For outdoor areas, like the town mentioned above, a 20’ x 20’ map square is common.

Second, draw the overall shape of the dungeon, based on the setting. For caves, no exact shape is needed; you could simply draw a line for the outer edge, break it with a few entrances, and fill the rest of the map paper with rooms and corridors. For a tower, however, you must decide on a size and shape before continuing.

Some sections of the map may be left blank, to be filled in later.


Stock the Dungeon

When building your adventure think about the overall ecology of the location. Would it make sense for certain monsters to exist together? Would they fight each other? Do they have a symbiotic relationship? Where do they eat? sleep? poop? Does the orc tribe have goblin servants? Is it a combat encounter or filled with dangerous traps?

Creating Combat Encounters

Combat encounters are the primary activities in any game. Whether it’s cleaning out a goblin infestation from someones basement or cleaning up a rogue necromancer’s evil undead army, it is important to understand how to create encounters that will challenge the players, but at the same time not kill them.

To build encounters, look to the experience value (XP) of each monster that you’re thinking to include.Take the combined total levels of the player characters and multiply it by 50 that will give you a nice middle of the range encounter for the players to fight through. Remember, this is a starting point and as the DM you can adjust the difficulty of encounters up and down by adjusting the number monsters.


Four 1st level characters ( 4 x 50 = 200 xp encounter) should get a good work out against 20 goblins. On the other hand, a Hill Giant (1200 xp) would completely destroy the entire party if it was encountered.


A trap is anything that could cause damage, delay or a magical effect to occur. The trap may be found, and possibly removed, by a thief character. Traps may be placed on doors, walls, ceilings, room furnishings (table,chest, etc.) or directly on a treasure. You may combine traps, or place several in one area, but try not to make the encounter too dangerous for the characters. Deadly traps are not recommended until the 2nd level of a dungeon (or deeper) is reached.

Some typical traps:

Blade: A blade sweeps out, down, or up, hitting someone (possibly allowing a Dexterity Save) for damage.

Creature: A monster (snake,beetle, spider, etc.) jumps up and gets 1 free attack by surprise.

Darts: Some tiny darts, shot by a spring mechanism, shoot out and hit someone (either automatic hits or by making Hit Rolls), for damage or some other effect (paralysis,poison, curse, etc.).

Explosion: Something blows up, causing damage to everyone in the area any set amount or dice range, but a Wisdom Save should allow damage to be reduced to half unless the explosion is an illusion.

Falling Items: A block (or rubble) falls when something is touched (or at random), striking someone and allowing a Dexterity Save (DC17) for trying to jump out of the way for damage (either a given number or a dice range).

Fog: Looks like poison gas, but a failed Wisdom Save results in (pick one): nothing, giggles, fear, a terrible smell for 1-6 turns (which may attract monsters or increase Wandering Monster chances), anger (victims attack each other for 1-4 rounds; a Wisdom Save may be applied), or paralysis.

Illusion: Something strange happens (but not really; see Phantasmal Force, a magic-user’s spell), and the characters may be scared away (or the illusion may have some other effect, such as giving a false clue, luring characters toward another trap, etc.).

Light: A bright light flashes, and all seeing it are blinded for a time (a Wisdom Save should apply, possibly with a bonus or penalty to the roll).

Pit: A section of floor gives way, and (one, some, or all) characters fall in, taking (ld4, ld6, ld8, ld10) damage. The pit may have something at the bottom (spikes for more damage, deep water, or a monster). It could be a chute, leading down (a oneway ride) to the next dungeon level.

Poison Gas: Victims make Constitution Save or take damage (ld4, ld6, or whatever is dangerous but not deadly to most characters). Additionally, a Constitution Save with bonuses(+1,+2,+ 4 ) to the roll may be made, with failure meaning death. Gas is usually in a container, released when opened.

Poison Needle: This is a small needle, hidden somewhere and nearly undetectable until accidentally touched, when it will spring out and poke a character who tries to open something.

Special Encounters

A “special” is anything you place which is not normal, but is not a trap, monster, or treasure. Some typical specials are:

Alarm: Summons special monster, opens dungeon doors, or has no effect at all.

Falling: Falling characters or monsters take 1d6 damage per 10 feet dropped. Dexterity Save for half damage.

Gelatinous Cube: This monster (AC 10, HP 24) is made of a clear jelly, usually in the form of a 10 x 10 x 10 foot cube (though other shapes are possible). It is hard to see, and it surprises often (+13). A gelatinous cube moves through the rooms and corridors of a dungeon, sweeping the halls clean of all living and dead material. In the process, it may pick up items it cannot dissolve (such as weapons, coins, and gems). It will attack any living creature it encounters. Any successful hit will paralyze the victim unless a Constitution Save is made. An attack on a paralyzed victim will automatically hit (only a damage roll is needed). This paralysis is the normal type (lasting 2-8 turns unless magically cured). A gelatinous cube may be harmed by fire and weapons, but not by cold or lightning.

Green Slime: Green slime cannot be harmed by any attacks except fire or cold. It dissolves cloth or leather instantly, wood and metal in 6 rounds, but cannot dissolve stone. Green slime often clings to walls and ceilings and drops down by surprise. Once in contact with flesh, it sticks and turns the flesh into green slime. It cannot be scraped off, but may be burnt off (or treated with a Cure Disease spell). When green slime drops on a victim (or is stepped on), the victim can usually burn it while it is dissolving armor and clothing. If it is not burned off, the victim will turn completely into green slime 1-4 rounds after the first 6-round (one minute) period. Burning does 1/2 damage to the green slime and 1/2 damage to the victim.

Illusion: A dungeon feature (stairs, room, door, monster, treasure, etc.) is not really there, but is merely a phantasm.

Map Change: A shifting wall moves after . the party passes, cutting off their exit. They must find another way out of the dungeon. The wall shifts back after a time (1 turn, 1 hour, 1 day).

Movement: The room (or stairs, or door, or item) moves (turns, drops, closes, rises, etc.) unexpectedly. It might be stopped if a roll for surprise (often with -1,-2,or -3 penalty) shows that the party reacts quickly enough to prevent it.

Pool: Magical water has a strange effect if touched (or drunk, or sprinkled on someone or something),such as healing, inflicting damage, changing an Ability Score, changing Alignment, making something magical for a time, invisible for a time, etc.

Sounds: The room (or item, or treasure) makes strange noises: moaning, screaming, talking, etc.

Statue: A large statue of a person, monster, or gadget (nearly anything you can imagine) is found. It may be valuable, magical, too heavy to move, alive, lonesome and willing to talk (maybe a liar), covering a trap door down, a treasure, etc.

Transportation: This could be a trap door leading up or down, secret stairs, elevator, magical portal to elsewhere (another room, another level, another dungeon), etc.

Trick Monster: This applies to any variation of a listed monster, such as: a skeleton who shoots its fingertips like a Magic Missile, a two-headed giant ogre, a “goop” dragon that spits green slime o r grey ooze, a wild bore (a shaggy man who tells long, dreary stories), a quarterling (half-sized halfling), a Mouth Harpy (who can’t sing but plays the harmonica), an Ogre Jelly (looks like an ogre, but . . .) Rock and Roll Baboon, and so forth.

Weird Things: You may let your imagination run, placing such things as: weapons which fly attacking by themselves, talking skulls, a magic item or treasure firmly stuck to the floor (or wall, or ceiling), a magical area (zero gravity, reversed gravity, growth to double size, shrink to 1” tall; effect lasts until leaving the area), a huge creature recently slain (too big to fit through the corridors get here?”), and so forth.

Yellow Mold: This deadly fungus covers an area of 10 square feet (“one” for No. Appearing), though many may be found together. Yellow mold can only be killed by fire: a torch will do 1d4 points of damage to it each round. It can eat through wood and leather but cannot harm metal or stone. It does not actually attack, but if it is touched, even by a torch, the touch may (50% chance per touch) cause the mold to squirt out a 10’ x 10’ x 10’ cloud of spores. Anyone caught within the cloud will take 1-6 points of damage and must make a Constitution Save or choke to death within 6 rounds.

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