Caverns
Under the earth lie twisting passages, vast caverns, and underground rivers, all cloaked in endless darkness. The environment itself can be just as dangerous as its inhabitants.
This generator lets you map a cave system. For Underland travel, see Underland Realm in Trials & Treasures.
Tiers. Tier 0 and 1 adventurers measure themselves against natural caves and caverns. Tier 2 and 3 adventurers delve deeper, into Underland itself.
Cavern Size. Each 70-foot-square node of a cavern contains either a cavern or a section of passage. A small cavern system is about 210 feet square (a 3 × 3 grid of nodes); a medium temple is 350 feet square (a 5 × 5 grid); and a large one is 490 feet square (a 7 × 7 grid). Underland is a vast megadungeon in which a single cavern system can extend for miles.
Treacherous Terrain. Naturally occurring caves are often slippery and riddled with pits and stony outcroppings. Whenever a creature uses the Dash action, it must make a DC 12 Dexterity saving throw at the end of its turn, falling prone on a failure.
Creating a Cavern
To generate a new map, roll on the Description table for the initial area and follow its instructions, and then do so again to see what’s past each exit, and so on. If you’re filling a premade map, roll on Inhabitants and Contents for each location.
Cavern: Description
| 1 - 2 |
Narrow passage. Roll on Passage Contents and Exits. At its narrowest, the passage is 1d6 + 1 feet wide. |
|
|
3 - 6 |
Passage. Roll on Passage Contents and Exits. The passage is about 10 feet wide. |
|
| 7 - 8 |
Wide passage. Roll on Passage Contents and Exits. At its narrowest, the passage is 1d20 + 10 feet wide. |
|
| 9 - 14 | Small room. Roll on Room and Chamber Contents and Exits. For room size, roll 1d4: | |
| 1 |
10 x 10 ft. |
|
| 2 |
15 x 15 ft. |
|
| 3 |
15 x 20 ft. |
|
| 4 |
20 x 20 ft. |
|
| 5 | 20 x 20 ft. | |
| 6 | 20 x 30 ft. | |
| 15 - 20 |
Large chamber. Roll on Room and Chamber Contents and Exits. For chamber size, roll 1d6: |
|
| 1 |
30 x 30 ft. |
|
| 2 |
30 x 40 ft. |
|
| 3 |
40 x 40 ft. |
|
| 4 |
40 x 50 ft. |
|
| 5 | 50 x 50 ft. | |
| 6 | 50 x 60 ft. | |
| 7 | 60 x 60 ft. | |
| 8 | 70 x 70 ft. | |
Cavern: Passage Contents
|
1 - 10 |
Empty |
|
| 11 - 14 |
Roll on Passage Scenery |
|
| 15 - 18 |
Roll on Escalations |
|
| 19 - 20 |
Roll on Obstacles |
|
Cavern: Cavern Contents
Roll 1d20 in small cavern, 1d20+2 in large cavern
| 1 - 3 |
Empty |
|
| 4 - 8 | Roll on Small or Large Cavern Scenery | |
| 9 - 11 |
Roll on Novelties |
|
| 12 - 14 |
Roll on Obstacles |
|
| 15 - 16 |
Roll on Discoveries |
|
| 17 - 19 |
Roll on Escalations and on Small or Large Cavern Scenery |
|
| 20+ |
Roll on Set Pieces |
|
Cavern: Exits
If the die roll is odd, a room's exits are blocked by doors. Otherwise, they are open
| 1 - 3 |
No Exits |
|
| 4 - 5 |
One exit left |
|
| 6 - 7 |
One exit straight |
|
| 8 - 9 |
One exit right |
|
| 10 - 11 |
Two exits, left and right |
|
| 12 - 13 |
Two exits, left and straight |
|
| 14 - 15 |
Two exits, straight and right |
|
| 16 - 18 |
Three exits, left, straight, and right |
|
| 19 - 20 | Ascent or descent. Roll 1d8. Then roll again on this table for other exits. | |
| 1 - 2 |
Sloping passage down |
|
| 3 |
Vertical climb down |
|
| 4 |
Vertical passage descending 1d4 levels |
|
| 5 |
Vertical climb up |
|
| 6 |
Stone spiral staircase up |
|
| 7 |
Trapdoor up |
|
| 8 |
Stairs going 1d4 levels up and 1d4 levels down |
|
Cavern: Novelties
| 1 |
Crystals or mushrooms that cast dim light cover the walls |
|
| 2 |
Stalactites and stalagmites made of transparent or invisible stone fill the area |
|
| 3 |
Rocks are coated with a reflective metal or algae that turns surfaces into distorted mirrors |
|
| 4 |
Natural, fluted stone pillars support high ceilings, giving the area the appearance of a temple |
|
| 5 |
An island sits in the middle of a lake of magma, silvery water, or ice |
|
| 6 |
A grove of trees or giant mushrooms |
|
| 7 |
Cavern spanned by multiple, naturally occurring stone bridges |
|
| 8 |
Tiers of towers, gates, doors, statues, and stairs are carved into the sloping rock walls |
|
| 9 |
A shield-sized crystal embedded in the ceiling sheds bright light throughout the area |
|
| 10 |
A chasm spanned by a narrow bridge or flat-topped pillars like stepping stones |
|
Cavern: Obstacles
| 1 |
Lock: Narrow passage, 3 inches wide, carved with the words “Gates of Gathor.” Key: A written command phrase, “Gates of Gathor, open the door,” which causes the passage to grind open to a width of 10 feet |
|
| 2 |
Lock: Passage choked with petrified fungus. Key: A nest of mouselike fungus creatures that eat petrified fungus |
|
| 3 - 4 |
Tight squeeze: at its narrowest, the passage is 1d12 + 10 inches wide |
|
| 5 - 6 |
Collapsed ceiling: An exit is blocked by 1d6 + 4 feet of rubble. The rubble can be excavated as if it were dirt |
|
| 7 - 8 |
Chasm: The chasm is 1d20 + 10 feet wide and more than twice as deep. At the bottom may be magma, an underground river, or another dungeon level |
|
| 9 - 10 |
Underwater area: The exit to an adjoining area is through a flooded passage that is 1d6 × 10 feet long. The adjoining area may be partially or fully underwater |
|
| 11 |
Fast-flowing underground river: The river is 1d10 + 10 feet wide. A creature that starts its turn in the river moves 60 feet downstream. The river may lead to rapids |
|
| 12 |
Magma: A 10- or 15-foot-wide stream of magma blocks the way |
|
| 13 - 20 | Trap or other exploration challenge (see Trials & Treasures) based on the dungeon level: level 1–2 wind tunnel or poorly repaired tunnel (T&T); 3–4 green slime hatch or hidden pit trap; 5–10 flammable gas trap or lethal outgassing (T&T); collapsing dungeon or sinkhole (T&T); 17–20 obsidian vine trap or perilous cliff path (T&T) |
|
Cavern: Discoveries
| 1 |
The key listed in entry 1 of the Obstacles table |
|
| 2 |
The key listed in entry 2 of the Obstacles table |
|
| 3 |
Pool of water containing 1d4 + 4 large, edible fish |
|
| 4 |
Pool of glowing water fed by a dripping stalactite. Drinkers gain blindsight out to a range of 60 feet for 24 hours. The water ceases to glow and loses its potency 1 minute after being removed from the pool |
|
| 5 - 6 |
1d6 fragrant mushrooms. If eaten, roll 1d4 to determine their effect. The mushrooms lose their potency 1 hour after being harvested |
|
| 1 | For 5 days, the creature gains the plant type, gains blindsight to a distance of 10 feet, and doesn’t need to eat | |
| 2 | The creature gains 3 temporary hit points per character level. While it has these temporary hit points, it has advantage on Perception checks that rely on smell | |
| 3 | The creature gains telepathy out to a distance of 120 feet until it finishes a long rest | |
| 4 | The creature gains the benefit of the detect magic spell until it finishes a long rest | |
| 7 |
Cache of supplies containing useful equipment and an incomplete map |
|
| 8 |
Corpse; among its possessions is a journal listing either the name of a powerful dungeon creature (see Set Pieces) or one of the treasures it guards (see Treasure Hoards) |
|
| 9 |
Lone creature from a guard patrol (1 or 2 on Escalations table), not particularly loyal and willing to talk |
|
| 10 |
Guard patrol (1 or 2 on Escalations table) escorting a prisoner; the prisoner offers aid or information to its rescuers |
|
| 11 |
Ore vein. If mined and smelted over several weeks, the vein produces 100 pounds of metal. The type of metal varies by dungeon level: 1–2 copper, 3–4 silver, 5–10 gold, 11–16 platinum, 17–20 mithral or adamantine |
|
| 12 |
Vein of gems. 1d10 gems can be collected without mining. If mined for several weeks, the vein produces a maximum of 50 more gems. The type of gem varies by dungeon level: 1–4 10 gp gem such as quartz, 5–10 100 gp gem such as garnet, 11–16 1,000 gp gem such as sapphire, 17–20 5,000 gp gem such as ruby |
|
Cavern: Escalations
50 percent of guards possess a Minor Treasure.
| 1 |
Guards: may attack intruders who don’t immediately show peaceful intent |
|
|
Level 1–2: 1d4 goblins |
||
|
Level 3–4: revilock with 1d4 grimlock technicals ; 2 ogres |
||
|
Level 5–10: dread troll , ogre mage , or fire giant |
||
|
Level 11–16: minotaur champion ; 2 fire giants |
||
|
Level 17–20: stone giant with 2 hill giants |
||
| 2 |
Guards: guarding a particular location |
|
|
Level 1–2: 1 or 2 troglodytes |
||
|
Level 3–4: kobold broodguard with 2d6 kobolds ; 3 or 4 bugbears |
||
|
Level 5–10: shadow elf champion warrior with 2d8 shadow elf warriors ; 1d4 + 5 azers |
||
|
Level 11–16: drider , shadow elf high priest , or shadow elf mage with 2 shadow elf champion warriors ; 2 driders |
||
|
Level 17–20: 2 cyclops myrmidons or cloud giants |
||
| 3 |
Guards: hunting |
|
|
Level 1–2: 1d4 swarms of bats or swarms of rats |
||
|
Level 3–4: black pudding |
||
|
Level 5–10: bulette or slime mold |
||
|
Level 11–16: giant grick with 3 or 4 gricks ; 2 purple worms |
||
|
Level 17–20: mutant rust monster and supermutant rust monster |
||
| 4 |
Guardians: in lair |
|
|
Level 1–2: 1d4 giant bats or giant centipedes |
||
|
Level 3–4: 1 or 2 mimics or wallflowers |
||
|
Level 5–10: 2 or 3 euphoria jellies or flash cubes |
||
|
Level 17–20: 2 cloakers |
||
| 5 |
Guardians: wandering |
|
|
Level 1–2: 1 or 2 gray oozes , rust monsters or violet fungi |
||
|
Level 3–4: 1 or 2 cave bears or dire centipedes |
||
|
Level 5–10: 2 stone sharks |
||
|
Level 11–16: purple worm |
||
|
Level 17–20: murmuring worm with otyugh ; 2 cloakers |
||
| 6 |
Denizens: warring against, or hiding from, local overlord (roll or choose from Set Pieces) |
|
|
Level 3–4: priest with 1d4 deep dwarf soldiers , deep gnome scouts , or scouts |
||
|
Level 5–10: 1 or 2 xorn |
||
|
Level 11–16: 2 champion warriors with 2d10 warriors ; 2 gladiators with mage |
||
|
Level 17–20: 2 fomorians |
||
| 7 - 10 |
Roll 1d6 on this table to determine an encounter group. The group is nearby (in the nearest unexplored room) and may be detected by tracks, noises, flickering torchlight, or other signs |
|
Cavern: Set Pieces
Set piece encounters usually feature a Treasure Hoard.
| 1 - 2 |
Hail the Conquering Villains. A raiding party has captured the residents of a rival settlement. They mean to exile, sacrifice, or even pit the captives against each other in gladiatorial games—and they’ll do the same to meddling adventurers. |
|
|
Level 1–2: kobold broodguard with 1d4 + 4 kobolds ; bugbear with 1d4 hobgoblins |
||
|
Level 3–4: bandit captain with dire wolf and 1d8 + 8 bandits |
||
|
Level 5–10: shadow elf champion warrior with 20 shadow elf warriors and either shadow elf mage or high priest ; 3 salamanders with 4 azers |
||
|
Level 11–16: minotaur champion with gorgon and 3 minotaurs ; storm giant with 2 frost giants and 2 ogres |
||
|
Level 17–20: ancient sapphire dragon with 4 kobold broodguards and 20 kobolds ; ancient red dragon with 2 half-red dragon veterans and 20 kobolds |
||
|
Setting: The chamber contains cages of prisoners. Releasing all the prisoners distracts the enemy combatants with the lowest CR, removing them from the battle. |
||
| 3 - 4 |
Exile. A powerful champion was exiled from its kind. Without allies, it considers every creature to be its enemy—or its prey. It might grant a few moments of life to creatures that offer it a way to hurt the creatures that exiled it. |
|
|
Level 3–4: hobgoblin warlord ; troll |
||
|
Level 5–10: deva |
||
|
Level 11–16: troll king |
||
|
Level 17–20: empyrean ; ]]King Fomor]] |
||
|
Setting: In other areas of the dungeon are groups of the creatures that exiled the creature (for instance, ogres in a level 1 or 2 dungeon). These creatures might join adventurers against the exile, or vice versa. |
||
| 5 - 6 |
False Adventuring Party. A group appears to be humanoid adventurers. In fact, they’re monsters that prey on the caverns’ humanoid denizens. If the characters talk to other cavern inhabitants, they may hear rumors of friendly seeming creatures who suddenly change form and attack. |
|
|
Level 1–2: doppelganger |
||
|
Level 3–4: 2 or 3 doppelgangers |
||
|
Level 5–10: 2 assassins or ogre mages |
||
|
Level 11–16: 2 rakshasas |
||
|
Level 17–20: vampire assassin , vampire mage , and vampire warrior ; 3 rakshasas |
||
|
Setting: The cave is filled with ill-gotten treasure—some of which is not what it seems. Depending on dungeon level, the treasure may be guarded by: |
||
| Level 1–2: false hoard trap | ||
| Level 3–4: mimic | ||
| Level 5–10: ghost trap | ||
| Level 11–16: nalfeshnee trap | ||
| Level 17–20: hidden cannon trap | ||
| 7 |
A cave-in behind the party seals off the cavern complex’s entrance. There are other exits from the complex, but they lead into miles of winding, deserted Underland tunnels. On each day of travel through these tunnels, the party’s navigator must make a Nature or Survival check to find their way. Three successes, or one critical success, allows the party to escape the maze. |
|
| 8 | The way is blocked by a settlement of deep dwarves, shadow elves, grimlocks, troglodytes, mycelials, or other underground dwellers. There are too many to fight, although the adventurers might be able to defeat or elude patrols. The easiest way through the settlement is to negotiate safe passage with its leaders. | |
Cavern: Minor Treasure
| 1 |
2d6 edible mushrooms |
|
| 2 |
Glowing lichen casts bright light for 20 feet and dim light for an additional 20 feet. The lichen glows for 1 month after it’s harvested |
|
| 3 - 4 |
Cultural equipment, such as deep dwarf stone of resolve |
|
| 5 - 6 |
Gems worth an amount appropriate to the tier (tier 0: 10 gp, tier 1: 100 gp, tier 2: 1,000 gp, tier 3: 10,000 gp, tier 4: 100,000 gp) |
|
| 7 |
1d6 vials. Roll 1d6: 3–4 potions of healing , 5–6 potions of greater healing |
|
| 8 |
Mushroom-based alcoholic beverage that causes drinkers to be poisoned for 1 hour. While poisoned, drinkers can cast clairvoyance at will |
|
| 9 |
Map to a valuable mineral deposit (see Discoveries 11 and 12) |
|
| 10 |
Cache of 1d6 magical shadow elf weapons made of dark iron: they’re +1 weapons but they crumble in sunlight. On dungeon level 11 or higher, they’re +2 weapons instead |
|
Cavern: Treasure Hoards
| Dungeon Level 1–2 |
Valuables: 1d4 × 100 gp worth of silver and gold coins or gems Magic (30 percent chance): gloves of swimming and climbing or vicious weapon |
|
| Dungeon Level 3–4 |
Valuables: 2d4 × 100 gp worth of silver and gold coins or 1d6 masterwork weapons worth 150 gp each Magic (40 percent chance): ring of resistance or wand of enemy detection |
|
| Dungeon Level 5–10 |
Valuables: 1d6 × 1,000 gp worth of gold coins, gems, or metal ore Magic (50 percent chance): ring of animal influence or wand of web |
|
| Dungeon Level 11–16 |
Valuables: 1d4 × 10,000 gp worth of gold and platinum coins or jewelry Magic (60 percent chance): ring of the ram or sword of sharpness |
|
| Dungeon Level 17–20 |
Valuables: 1d4 × 100,000 gp worth of electrum, gold, and platinum coins and jewelry Magic (70 percent chance): Harvest or ring of invisibility |
|
Cavern: Passage Scenery
| 1 - 2 |
The passage twists and turns: visibility is reduced to 10 feet |
|
| 3 |
The passage climbs and drops; it is difficult terrain |
|
| 4 |
The passage has a three-foot ceiling; Medium creatures must crawl |
|
| 5 |
The passage is a fissure with a ceiling hundreds of feet high |
|
| 6 |
The passage’s walls are wet |
|
| 7 |
The passage’s walls are covered with stone spikes. A creature pushed into a wall takes 3 (1d6) piercing damage |
|
| 8 |
The passage is crossed by a shallow, 10-footwide stream that emerges from and flows into narrow flooded tunnels |
|
| 9 |
The passage is round and perfectly smooth. DC 13 Nature check: it may have been bored by a purple worm |
|
| 10 | The passage is a round tube with a deep fissure stretching its entire length. A stream runs at the bottom of the fissure | |
Cavern: Small Cavern Scenery
| 1 |
The floor and ceiling are festooned with stalagmites and stalactites. The area is difficult terrain |
|
| 2 |
Stalagmites, stalactites, and columns make most of the cavern difficult terrain , though there is an open space in the middle |
|
| 3 |
Delicate sheets of stone hang from the ceiling like drapery |
|
| 4 |
Translucent crystals cover the walls and ceiling. Crystal columns connect the roof and floor |
|
| 5 |
Surfaces are covered in a delicate lattice of white crystals that resemble frost or snow |
|
| 6 |
Lovely stone formations that resemble lilies grow from the floor |
|
| 7 |
Walls, stalactites, and stalagmites are fluted with thin, vertical channels |
|
| 8 |
Crystalline, hollow stone tubes, an inch or two thick, hang from the ceiling |
|
| 9 |
Stalactites of vivid blue, green, and yellow hang from the ceiling |
|
| 10 |
The cave features a bubbling, geothermal pool. Once per day, a creature can bathe in the pool during a short rest to recover 1 level of fatigue |
|
| 11 |
A waterfall spills from a hole in the wall or ceiling to feed a subterranean lagoon |
|
| 12 |
A perfectly still pool is disturbed every few minutes by a drop of water from a stalactite |
|
| 13 | The floor is submerged in 1d4 feet of water | |
| 14 | The cavern features a pool with a stalagmite-covered island in the middle | |
| 15 | The cavern features an open pit filled with a pool at the bottom. There’s a 50 percent chance that the pool contains a Minor Treasure | |
| 16 | Vertical shafts in the ceiling or floor lead to the room’s exits | |
| 17 | Half the cavern is a sunken area, 10 feet lower than the rest | |
| 18 | The cavern is composed of two chambers connected by a narrow opening | |
| 19 | A column 5 to 15 feet in diameter dominates the center of the cavern | |
| 20 | The cavern contains an abandoned camp, including tents, firepit, and old refuse. There is a 50 percent chance that a Minor Treasure is found among the detritus | |
Cavern: Large Cavern Scenery
| 1 |
The floor and ceiling are festooned with stalagmites and stalactites. The area is difficult terrain |
|
| 2 |
Purple worm skeleton |
|
| 3 |
Sharp, translucent crystals cover the walls and ceiling. The floor is difficult terrain . Foot-wide crystal bridges crisscross the cavern |
|
| 4 |
Lovely stone formations that resemble lilies grow from the floor |
|
| 5 |
The cavern features a wide, still lake. Stone pedestals serve as stepping stones |
|
| 6 |
Waterfalls spill from the wall or ceiling, feeding a lake or river |
|
| 7 |
Stone pillars rise from a lake to support the cavern’s high, arched ceiling |
|
| 8 |
A river meanders down the center of the cavern before draining into a vertical shaft |
|
| 9 |
A steaming lake surrounds an island. A creature that begins its turn in the lake or enters it for the first time on a turn takes 5 (1d10) fire damage |
|
| 10 |
Craggy islands dot the surface of a vast, underground lake |
|
| 11 |
The room’s exits can be reached only by climbing the cavern walls |
|
| 12 |
The cavern is composed of two chambers connected by a narrow opening |
|
| 13 | Magma cascades through a hole in the ceiling, feeding a meandering magma river | |
| 14 | The ground is hot to the touch, burning unprotected feet. A weight of 500 pounds placed on a particular 10-foot-square area of floor, or dealing 10 bludgeoning damage to an area of floor, causes it to crumble into a magma chamber below | |
| 15 | The cavern is ringed by several tiers of naturally-occurring balconies | |
| 16 | The wreck of a subterranean sea vessel | |
| 17 | Natural stone bridges crisscross a lake of magma or water | |
| 18 | The cavern stretches hundreds of feet above or below the entrance. Exits may connect to other dungeon levels | |
| 19 | A forest of giant mushrooms, each dozens of feet tall, fills the cavern. The area is difficult terrain , and visibility is limited to 10 feet | |
| 20 | A lake of glowing white or pitch-black water fills the cavern. Water taken from this lake functions like a light or darkness spell for 24 hours | |