Thursday, December 18, 2025

Undercroft: Dungeon Builder and The Weird


This is a dungeon builder for His Majesty The Worm. You use it a bit like the City Builder in the corebook, but for the underworld. It’s based on the one from Esoteric Enterprises, my favorite dungeon builder ever.

HOW TO HOST A DUNGEON
This builder uses the Major Arcana without the Fool. Use the largest piece of paper you have available to you. You can use a normal letter size piece but it’ll feel crowded fast.

DEAL
Shuffle and deal out the Major Arcana face up on the page. You can place the cards wherever you want. Each card will be one room, so deal out however many you want to have in this node of the dungeon. The maximum is twenty one, unless you want duplicates. Once this is done, remove the cards one at a time and write the value in the corresponding position on the page, along with whether that card was dealt upright or reversed (upside down).

CONNECT
Once you’ve got your cards on the page, it’s time to build connections. Draw lines between rooms which are adjacent to one another. What counts as “adjacent” is up to you, just don’t leave any rooms isolated. You can make a big loop and avoid drawing connections through the center, tie everything to a central cluster of chambers like a spiderweb, or anything in between. 

If you like you can do this part after going through the ROOMS section to determine what’s in each area. Knowing what’s going on in each room can help you decide what’s logical or fun to connect (and stop the players immediately getting stuck if the one way through is impassable). 

INTERLINK
According to the overall orientation of your underworld, draw connecting passages from the rooms closest to the map edges to the corresponding rooms in other underworld areas. Add up or down staircases/ramps/shafts to shallower and deeper levels, to the Ossuary, or to the City above. Like Connecting rooms within a dungeon node, connecting to other maps of the undercity is hand-fitted according to your own desire for how the players should move through the overall dungeon.

POLISH
You can just show the players the balls-and-sticks map with the arcana values written on it, or trace over your map on a new sheet of paper and draw something nicer. Keeping the original copy for internal reference lets you write things on it that are easy to forget in play, like if noise in one room will draw monsters from adjacent rooms.

Some rooms have Treasure, Books or Small Change in them. If you see this, draw a card from the Minor Arcana and use it to stock that room. You can draw beforehand for every room that has the treasure descriptor, or wait until the players arrive.

Saftleven 
 
EXAMPLE AREA: THE WEIRD
All these procedures would be useless without rooms to arrange, no more labor saving than handmaking everything yourself. I hope to create one of these for each of the four magic realms. This one is an abandoned wizard lab, twisted by residual magic from the land of dreams.

CONNECTIONS IN THE WEIRD
The connecting passages between rooms are determined by the value and orientation of the rooms they link together.

Upright Odd to Upright Odd: A corridor wide enough for two people to walk side by side and a plain, wooden door, unlocked.
Upright Odd to Upright Even: A corridor wide enough for two people to walk side by side and a plain, wooden door, barred from the even side.
Upright Odd to Reversed Odd: A narrow corridor wide enough for one person. A wooden door reinforced by metal, barred from the even side, with a viewslit to admit sight and sound.
Upright Odd to Reversed Even: A corridor wide enough for two people to walk side by side, terminating in a metal portcullis with no attached mechanism to lift it.
Upright Even to Upright Even: Narrow passage bored by monsters or magic, no doors.
Upright Even to Reversed Odd: Passage large enough for a wagon to pass through, separated by a heavy curtain. The cloth is warded and blocks the passage of spirits.
Upright Even to Reversed Even: Corridor wide enough for one person, wooden door unlocked but blocked from odd side by heaped furniture and rubble.
Reversed Odd to Reversed Odd: Notable elevation difference bridged by a vertical shaft halfway down the corridor. Pulley mechanism for lifting goods but no rope or crank.
Reversed Odd to Reversed Even: Enchanted stone door with no visible locking mechanism, opens with a command word.
Reversed Even to Reversed Even: Magic door opens from one room to the other with no intervening corridor. Removing runestones from the doorframe closes the portal.

Parkinson

ROOMS IN THE WEIRD
I: Teleporter room. Straw training dummy with enormous executioner ax next to ring drawn in luminous green chalk on stone floor. The circle transports anyone who steps across the line to a corresponding location in the City, and vice versa. The dummy is a crude security system, it swings the ax at head level whenever anyone passes through from the City side. 

II: Parlor. Coffee tables, luxurious chairs and couches, thick rugs, enchanted windows that show random dreams from the City above. The furniture is enchanted and will react to anything the Guild says that sounds like a command, potentially injuring them with its eagerness. Pipeweed and Small Change abandoned here.

III: Fire room. Glowing pillars shine white like brilliant marble, actually white hot metal. Molten channels that glitter like mercury, crossed by stone bridges of purple volcanic stone. Collapsed bridge stops progress from one half of the room to the other. Slagged machine with boiler and pipes, created in failed attempt to extract quintessential elemental form of fire.

IV: Water room. Completely flooded chamber with tropical coral ecology, fish, octopuses, sharks… Floating platforms surrounded by large air filled bubbles allow passage. Isolated bubble with Treasure can only be reached by swimming.

V: Lightning room. High ceiling lost in whirling clouds that crackle with energy, floor scattered with man-sized crystals. Metal objects held by characters spark ominously. Anyone in metal armor risks critical damage from lightning strikes. The heavy crystals can be rearranged to direct the lightning.

VI: Earth room. Nonstop rain of fist-sized iron balls from fissures in the high ceiling, clattering off jagged stone formations and slipping into crevices in the earth. A central gazebo with a steel roof offers shelter for those who brave the storm.

VII: Lotus room. Inky black flowers (virulent sport of Ghost Lotus) overflow from planters. Adventurers feel drowsy, if a fight breaks out they are Stunned (one less card). Cushions around low table with vaporization lamp, pipes packed with oily black resin. Smoking the flowers places the user in a coma as their mind ventures to the plane of Dreams. They will not wake unless roused with stimulants (smelling salts, drugs, etc).

VIII: Microgravity room. Spherical chamber full of floating furniture. Characters float freely and must push off surfaces to navigate. In battle everyone moves one Zone automatically on each occupied Initiative count until they hit a wall. Two units of Small Change floating.

IX: Dining room. Globes of light hover over ring-shaped table around a central platform full of instruments. Small Change on the table, approach and the instruments play themselves loudly, prompting a draw on the Meat Grinder (ignore if not an encounter).

X: Damaged orrery. Clocks and mechanisms fused together. Models of planets and stars dangle uselessly from metal rods. Extra moon from land of Dreams, erratic course perfectly plotted before the whole thing broke.

XI: Locked room. Scorched, walls smeared with ash, silhouettes of wizards annihilated in a fireball. Remains of chalk circles and candles on floor, grazed on by 1 to 4 (use suits of Minor Arcana discard) Ungoats.

XII: The vats. Glass alembics and tubes connected to barrels and stills. One of the vessels is broken, strewing the floor with glass shards and toxic ooze. A Slime hides amid the wreckage, waiting for prey to envelop. Hermetic Bottles and an Alchemy Kit can be retrieved here.

XIII: Ransacked library. Books tossed and scattered by frantic searchers, pages torn out by vandals, remainder smeared with the droppings of vermin. [Minor Arcana Discard] Face Rats nest here amid the stacks, eating the bindings and the leather. Two Books salvageable.

XIV: Domed room with glistening pool. The shimmering pond casts light on the ceiling and shows images of other worlds. A mountain made of glass. A floating world besieged by exploding ships. A city in space. A dagger fight in a tunnel filled with insects. 

The portal leads to the Weird, plane of dreams. Objects dropped into the pond shimmer and become something appropriate for the world shown on the other side, before the focus shifts and they disappear for good. Characters who jump through the portal become characters in the dream, transformed and with no memory of who they were.

XV: Treasure room. Locked chests, cabinets full of glowing potion bottles, racks of shining weapons. Every one is a Mimic. A single one has a real Treasure inside it.

XVI: Bedroom. Gargantuan granite statue of crowned ram pointing sceptre at dead, dessicated wizard on mattress. Atop statue’s head inside crown are sleep settings, currently set to COMA. Anyone who passes in front of the sceptre falls asleep until dragged out of its line of fire. Collar and chain attached to bedpost, lock picked. Small Change and colorful wizard robes in cabinets.

XVII: Gallery. Toppled shelves with heaps of taxidermied, pickled and even vitrified monsters in glass. The slurry of glittering liquid on the floor inflicts random mutations per the rules on page 307 of the corebook. A dead face rat with two heads floats in the slime to illustrate the danger. Hop across the furniture to stay dry. An alchemist can extract a couple organs from the mess, the rest are too damaged.

XVIII: Cloud chamber. Chilly, damp, visibility limited. Thick fog allows observation of individual particles emitted by magic. 

XIX: Cerenkov room. Chamber made of enormous hexagonal stone columns, like Giants’ Causeway. Blue glow emits from stones. [Minor Arcana Discard] Bloodybones slobber all over the rocks, slurping up the radiation. Every watch spent here reduces a random stat by one.

XX:
Kitchen. Convenient but dangerous magical appliances. Heat ray oven, ice magic fridge, animated sword blender. All enormous, heavy, bolted down to stop them rocketing around the room under recoil. Food, booze, cutlery, Small Change.

XI: Genie garden. A sanctuary with flowing fountains and beautiful gardens that glow in the gentle light of smokeless flames. The vaulted ceiling is studded with geometric fractal patterns for the spirit to rub on. The Jinn hates wizards but loves puzzles. Two Treasures in his paradise.

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Le Cain
 
MEAT GRINDER IN THE WEIRD
I: Torches gutter
II: Torches gutter
III: Torches gutter
IV: Torches gutter
V: Torches gutter
VI: Surfaces glistening with slime.
VII: Pieces of metal armor and equipment, pitted with digestive acid and regurgitated by an Umber Hulk.
VIII: Fractal patterns of the type enjoyed by Jinn, burned into the wall.
IX: Hasty sketch of a treasure chest attacking an adventurer.
X: Random Book abandoned here.
XI: Torrent of random element (Minor Arcana discard for which) flows through room, heralded by ominous sounds of rushing water/rolling boulders/roaring wind/consuming flame.
XII: Glittering wave of thaumic energy surges toward the Guild. Anyone caught without grounding is teleported to a random room.
XIII: Billowing cloud of solid fog slowly forces the Guild forward, cutting off their escape.
XIV: A connecting passage moves on its axis, linking up to a different room at the other end.
XV: Another room superimposed over the current one as the Dream shifts. Draw from the Major Arcana to see which one.
XVI: Dark Creeper, in search of arcane treasure to steal.
XVII: Jinn, floating down the corridor as a serpent of fire.
XVIII: The Triplets, looting the place.
XIX: [Adventurer] Brain Spiders, in search of intelligent prey to decerebrate.
XX: Cave Hulk, hiding in a burrow behind a wall to ambush prey.
XI: Quest rumor

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