Inside a dungeon

The way in

A building on the surface marks it.

Depending on the biome it is a castle keep, a round tower, a stepped pyramid or a columned temple, built in that biome's materials - sandstone in the desert, blackstone in the badlands, ice on the peaks. Vanilla's own /locate structure crawlspace:dungeon finds one.

▸A book of rumours on a lectern in the first room tells you what is below. Not all of it is true.
▸Arriving on a level shows its number and theme, and sometimes its mood: hollow walls (more secrets), damp air (pools everywhere), darkness (no lanterns, better loot), many feet (more monsters), clicking floors (twice the traps), or something large hunting the halls - an elite that tracks you room by room, and you hear it coming.
▸The block over a doorway says what is inside: gold-flecked blackstone for treasure, amethyst for a shrine, a bookshelf for a puzzle, iron for a guard room, and a wither skull over a lair.
▸A spiral stair joins the levels. Pits drop you a level into a pool, and where a room sits over a room there may be a second stair.

A CrawlSpace castle keep seen head on, the entrance door at its foot — The keep. The stair down starts inside.

Rooms

Thirteen kinds of room, dressed for what they are.

Each theme builds its rooms in its own blocks, and each role adds its own furniture: sarcophagi in a crypt, mess tables in a guard room, altars in a shrine, pillars and arches in a hall.

Room	What it is
Entry	The first room on a level, at the foot of the stair from above. The lectern with the rumours is in the top one.
Exit	The room with the stair down. There are always two ways to reach it.
Room · Hall	The ordinary rooms of the loop, with a few monsters each, and the long pillared halls.
Guard room	Wakes its monsters together as you approach. From the first level it may hold a spawner - and some guard rooms are survival rooms, numbered guards, or a sentry post.
Treasure	Chests and barrels rolled by depth. Some are vaults: three treasures on three pedestals, take one and the cages slam shut on the others. Some are barred token vaults, opened by feeding a cauldron the tokens that level's guards carry.
Secret	Behind a wall that crumbles when you find it. Without a perception mod the wall is built from a related but different block, and gives off faint green particles near you.
Lair	A named boss with a boss bar, and its hoard. Some lairs sleep, some keep a prisoner, and the deepest one is the finale.
False lair	A pretender's. Its boss falls too easily, and something far worse growls from behind a secret wall.
Objective	A set piece a storey taller than the rest, with a job to do. Five kinds, below.
Shrine	An altar you may use once, for its gift: Sight (every monster near you glows, even through walls), Vigour, Swiftness, Warding or Fortune. Some are cursed, and the dead answer. An unused altar shimmers with enchanting glyphs.
Key room	At the end of a branch, with a floor lever that opens the level's locked iron doors.
Puzzle	A maze over the void, an ice board or a teleport maze, with a hoard at the end and a seal for the bottom door in it.

Traps

Eight kinds, and each fires once.

A trap is a pressure plate or a tripwire. Some plates are decoys; without a perception mod the real ones give off faint red sparks near you, and with one they stay hidden until your character spots them. Break the plate, or sneak and use it, to try to disarm it - and it might go off in your face.

Trap	From level	What it does
Dart trap	1	Darts from the nearest wall.
Alarm	2	A bell: every sleeping room near it wakes.
Web trap	2	Cobwebs burst round you, and you are slowed.
Gas trap	3	A cloud of poison where it was sprung.
Rockfall	3	Stalactites drop from the ceiling on to you.
Frost trap	3	A freezing mist.
Fire trap	4	Flames from the floor round you.
Ambush	4	Monsters burst out round you.

Tells. Most traps leave signs nearby: a skull, a dead plant, a pebble, frost, a scorch mark, sculk. Learn to read them - or, with LegendQuest, let a Perception roll read them for you.

Pits and crumbling floors. Some floors give way into dripstone spikes, and some drop you to the level below. Portcullises drop behind you and one-way doors close, so the way you came in is not always the way back.

Mimics, from the third level: the odd chest bites, or is trapped. Kill a mimic for what the chest held.

Puzzle rooms

On nearly every level, and a solved one blesses you.

About nine levels in ten have a puzzle room, and a quarter have two. Opening a solved puzzle's hoard gives a buff for six minutes, and the hoard holds one of the seals the bottom door wants.

Mazes over the void

Narrow paths over nothing, with gaps, crumbling stones and dripleaf deeper down, and a leap of faith you find by throwing things. Step off and the void sends you back to the start - unless your character catches themselves.

Ice boards

A floor of blue ice, seven across, with stone pillars standing in it. Cross every tile exactly once, each step beside the last; skip one or step off and the board cracks back. While you are out on it, a monster comes every ten seconds or so, with knockback. The pillars are always placed so it can be done.

Teleport mazes

A three-by-three of sealed cells joined only by pads in the floor. Find the pad that reaches the centre, where the hoard is.

Encounters

Monsters wake as you come near. Some of them have a plan.

No endless spawning: a room wakes its monsters once as you approach. Spawners turn up from the first level, multiply deeper down, ignore the light, and burn out after a while, so a dungeon cannot be farmed for ever.

Bosses and champions

Every lair has a named boss with a boss bar - the Dune King, say - and champions with powers of their own. On a NeoForge server they are scaled up; on 1.20.1 they are normal size.

Sleeping guardians

Some lairs above the bottom sleep, snoring. Sneak, and you can take the hoard from under their noses; stand up, strike, or creak a chest open, and the whole pack wakes. A moment on your feet is still quiet, so you can open a door or a chest.

Prisoners

Some lairs keep a captive behind bars. Kill the beast, then free them: they leave you something, and tell you something true about the dungeon.

Survival rooms

Some guard rooms drop their bars once you are inside: hold out for a minute against waves, with the countdown shown to everyone in the room, and the doors open on a chest.

Numbered guards

Monsters with numerals on their brows: kill them in order, I to IV, and a chest appears. Out of order, and the one you killed rises again and pays nothing. From the third level down every one you have killed rises, and you start from I.

Sentries

Some guard rooms post a Sentry with a goat horn. If it sees you, you have three seconds to kill it before it sounds the alarm and the nearest rooms come for you. Sneak to get closer.

The gelatinous cube

A wall-to-wall cube of green jelly glides along a corridor, its last meals frozen inside. Touch it and it engulfs you; kill it and what it swallowed spills out, some of it still alive.

The thing you should not touch

A sealed tomb ringed with skulls, warning you off. Open it anyway: it pays at once, and the Restless Dead fill every room you cleared on that level until you leave it.

The dungeon clock

Every 45 seconds the dungeon rolls a die, and on a 1 something happens: a wandering band you hear coming and from where, a sound in the dark, the light snuffed out, a swarm, a curse, a ghostly knight's warning, a stranger who will trade, falling rocks, or something glinting at your feet. Fighting is noisy and makes it likelier.

Objective rooms

Big set pieces, each with a job to do.

After the room cards of the old dungeon board games, in rooms a storey taller than the rest, dressed to match. About half of a dungeon's middle levels get one. The first time you go in, a band from the level below comes for you. Do the job for a reward chest and replay tablets, and the way out is part of the set piece: it looks like the stone around it until the job is done, and takes you straight to the surface.

The Fighting Pit

Three deep, with a barred cage in its far wall, bones and spikes on its floor, one lamp hanging over it and a gong on the rim. Jobs: the Pit Champion, and the Pit Guardian that waits in the cage.

The Firechasm

A chasm with lava three blocks down, crossed by a plank bridge that gives way behind you and mends after ten seconds; some planks are rotten and snap at once. A blackstone dragon sits on the far side, wings spread up the wall. Jobs: the relic on its pedestal, and the dragon's stolen eye, which the Eye-Thief carries.

The Fountain of Light

A round basin with glowstone under the water and a raised bowl spilling light. Jobs: find the one stone of the rim that gives a vial (every wrong stone wakes a guardian) and pour it in the dry basin; or cleanse the corrupted stones, each of which calls two guardians from the level below.

The Tomb Chamber

The sarcophagus on a raised plinth, a skull at its head, soul lanterns on four posts. Jobs: the Tomb Lord; or break the tomb, one blow a second, while every blow calls the dead to it - up to twelve about it.

The Idol Chamber

A gold idol enthroned on a sandstone dais, red-eyed and horned, a burning orb before it. Jobs: the Shaman; or stop the summoning before the bar fills, because if you are too slow the Shaman ascends and becomes a boss.

The finale

The deepest lair's boss sleeps in a sunken arena until you set the seals on its altar and offer a gold ingot. The altar wants a seal from each level above that has a lair (from its boss) or a puzzle (in its hoard). A vault token stands in for a missing one, and after half an hour on the bottom level the altar takes gold alone.

Beat it, and the altar can call it back - Recalled II, III and so on - stronger each time, with a richer hoard.

Restocking

Every twelve real hours a dungeon fills again: its rooms wake, its traps re-arm, its chests refill as they are next opened, broken chests and barrels come back filled, and every wooden door is shut again. Never while someone else is inside - it happens as someone arrives.

The hours are a setting, and 0 means never.

Replay tablets

Objective rooms pay in tablets. Read one in a dungeon and it wakes again at once, harder, for everyone in it, until the bottom boss falls. Each tablet carries one boon - twice the experience, chests a tier richer, blessings twice as long, or monsters that carry gold - and one bane: half again their health, half again as hard, half again as many, or champions twice as common.

Tablets work in any dungeon, so they can be collected, traded, and combined.

Loot

Five tiers by depth. Mending books, rare enchantments, armour trim templates, the netherite upgrade, and trimmed, enchanted armour at the bottom. Prisoners, shrines and solved puzzles pay on top.

They are ordinary datapack loot tables - crawlspace:chests/tier1 to tier5, plus supplies - so a pack can change them.