6-Room Dungeon 7: Underland Cavern

1 Redbrick
2 Goblin Mine
3 Gothic Tomb
4 Magic Mansion
5 Glacial Chasm
6 Jungle Shrine
7 Underland Cavern
8 Auldwood Grove
9 Sunken City
10 Desert Ruin
11 Eldritch Monolith
12 Hell Gate

Possible extra tables for each category
d12 factions
d12 factions

Has fun with my weekly club D&D and a cthulhu session with all women players (one played a woman as a agatha christie style mystery writer). Reading current dragon adventure book and its quite fun and modern and like the different art styles - i will use some of these soon. They are fun which reviews seem to not mention.

Underland Cavern
This is the deep caves where beings of the deep dwell and not just visited by fearful surface adventurers. Weird creatures dwell here and may preserve creatures lost on the surface world. Beings from the age of darkness were driven below when that age ended and great floods drove others into the underland. As many of the prehuman and fey beings of the deep tend to be horrible, they often trade in slaves from the surface or far away lands. Many weird factions below wage trade and war constantly and most have a sense of preservation and curiosity. Various factions will determine what pets, allies and servitors will be with any intelligent force. Some might have declined or mutated from isolation or lack of change

d12 Underland Cavern Decor
1 Dripping stalagmites, stalagtites and natural stone pillars

2 Petrified trees or animal fossils from the prehuman age

3 Bubbling water or mud pools

4 Flowing or dripping water or pools
5 Ancient cave paintings or relief rock art

6 Remains of campfire or burned-out torches or lanterns

7 Luminous fungus, fish, spores or bugs

8 Sinkhole or shaft up or down

9 Fungus garden full of giant vermin or tended neatly

10 Stone bridge over deadly chasm

12 Writing or marks from past explorers

d12 Underland Cavern Hazards
1 Shaft to climb up or down

2 Dangerous vapours possibly poison, diseased or flammable

3 Chasm over lava, spikes, a bottomless pit or water, with a feeble rope or a stone bridge

4 Pool or a stream of boiling water, mud or lava
5 Toxic minerals, salts or nitrates and mineralised creatures and lurid colours

6 Nest or colony of vermin like bats. easily startled

7 Cave ambush predator concealed

8 Series of tight squeezes or semi-collapsed areas

9 Natural deadfall of rubble or some deliberate trap

10 Deadly fungus, mould, spores or killer slime. Poisonous or carnivorous or full of dangerous creatures. In rare cases of unnatural magic, light may have ancient plant life instead

12 Ancient slumbering colossal monster

d12 Underland Cavern Encounter
1 Giant beetles or worms or scorpions or spiders

2 Giant rats or bats or carnivorous moles

3 Bears, owlbears or hook-handed horrors

4 Undead looking for human, may be fungal or parasitic based
5 Giant amphibians, frogs, toads or salamanders

6 Reptilians like albino dinosaurs, giant lizards or snakes

7 Giant isopods rolling along in balls

8 Abhumanoid or demihuman locals (trabal or civilised)

9 Lost explorers or cultists oe escaped slaves

10 Elemental earth creature from a plane or a hybrid with an animal

12 Land sharks or gigantic bug or worm

d12 Underland Cavern Static Encounters
1 Living statues

2 Giant slugs or snails grazing on fungus

3 Mixed giant vermin, including leeches, crickets, beetles and centipedes

4 Cave fisher or giant cave lobster pool
5 Tentacled horror of the deep, covered in eyes and gibbering mouths

6 Lycanthrope (d4 1=bat 2=spider 3=snake 4=rat)

7 Roper, mimic, trapper or piercer hidden as natural formations

8 Fungus or slime creatures

9 Dark fey, including elves and goblins, kin to fungi and with a pet

10 Elemental being most likely earth

12 Evil spirit or demon

d12 Underland Cavern Entry
1 Beast den cave with nest and food scraps. Possibly hunting or at home, and might have a mated pair and children. Older passages branch off and are unused by any beasts

2 Old mine likely abandoned, but has passages linking to natural tunnels. Often rubble, tools and old beams lay about, even workbenches and buckets of rocks. Some kind of miner, human or humanoid may remain or protective mine spirits or undead miners. Other creatures might move in if mine emptied

3 Grotto cave with water and spectacular mineral formations. May be inhabited by a hermit or magical creatures or some spirit. It might often be a shrine and used by cults or rustic magicians. Other cave passages branch from the main room. Magic pools may form in such caves with strange powers. Some have strange lights, mist or crystals

4 Sinkhole into a large cavern with pools and flowing water. Perhaps remains of animals fallen in and perhaps long extinct are here. Vegetation may grow with sufficient light or fungus. Various passages lead out
5 Cave tomb partly carved, possibly simple or ornate, Inside is a chamber of burial niches and a stone sarcophagi and various passages, May be long bare and used as a lair for beasts or bandits or a cult. Sealed complexes more likely to have undead

6 Crack in the earth exposing an underground cave chamber with various passages

7 Tribal cave where a clan of wild folk, beast folk or humanoids dwell. There is cave art, grindstones, flint tools and preserved food. A clan may live here or perhaps just haunted by spirits

8 Gruberhole, a robber's cave where a degenerate clan of robbers dwell, possibly with prisoners and a family. The worst may also be inbred cannibals or cultists. The more professional bandits may be led by a robber knight or outlawed noble

9 Giant burrow of some huge beast into a chamber with more passages and natural caves. It may be present or long extinct. Other creatures may use it as a lair or family home for humanoids. Trolls or giant worms are good creatures to use

10 Temple cave may be minimal or ornate with relief carvings or paintings. An altar, fire pit and idols will be present. Religion might be long gone, have a living cult or perhaps a raiding band of plunderers from the surface or the deep. A cult guardian monster or spirit might guard the temple. There may be rich decorative items hidden here
11 Earth Gate was used by ancient subtereaneans and faerie folk as secret outposts to spy on humans. Often, earthen mounds with some vegetation from afar. The entrance will be partly overgrown and possibly hidden by cunningly hidden doors. These might have even have been used for trade with the surface. Mixed household goods may be scattered in rubble or intact with dust or warm from recent use. Creatures or former pets might live here or servitors like goblins or kobolds. Might be a fully operational spybase of a hidden people with militaristic professionals, or perhaps a family of harmless small folk

12 Hellgate cave used by a cult to depict hell to terrify initiates and captives. The chamber will have passages carved with relief art or paintings of underworld terror. Some may be enhanced with illusions or natural volcanic vents, steam or hallucinogenic vapours. Cults and summoned beings may use or guard, but normal creatures will shun this place. Other passages may have been used by the cult

d12 Subroom
1 Well or shaft down

2 Sinkhole to above

3 Tomb with a body, possibly an undead

4 Fungus room with edible or exotic groths
5 Cell used for prisoners or animals

6 Shrine with idol and altar

7 Quarters with bed and possessions

8 Supply cache 

9 Beast nest, vermin or worse

10 Reliquary with strange, possibly prehistoric ritual items
11 Hibernating creature nest or magical sleeper

12 Colony of fiesty vermin, possibly giant

d12 Major Room
1 Mud cave with a clay pit and slippery mud everywhere, depth may vary and giant bugs and critters may lurk in muddy jholes and pits

2 Ice cave or freezing air with frozen bodies in ice walls. Some might come here to thaw food or plunder the dead. Cave might be thawing or sensitive to heat brought in it. Heat is drawn out through air currents. May be used as a cool room by a faction or a larder for a monster. Some species may use as a hibernation chamber. Fragile ice crystals may fall, and the remains of the dead here might be undead or have loot

3 Gallery cave with prehistoric art of the underground peoples. Once used for rituals may have poltergeists or lesser spirit

4 Ambush cave where a monster or faction uses a choke point to attack. Some prefer water or height advantage or some hazard to avoid
5 Fungus cave with giant glowing fungus and huge, possibly giant bugs, edible or possibly magic mushrooms or dangerous fungus

6 Shrine cave with stone idol, fire pit, altar and wall art. Offerings may be here and if not abandoned, may have underground peoples visiting for ceremonial reasons

7 Tomb cave with burial niches and possibly undead with grave goods. May have been looted long ago and now monsters or humanoids lair here

8 Fortified cave where a faction built a controlled barricade with wall, a walkway and high points for archers. May be made of bones, scaffolding or garbage. May be abandoned or occupied by a faction

9 Lair cave or a monster or beast with remains of kills and often treasure among body parts

10 Outpost cave, where a faction's scouts camp when checking area, may be well settled or abandoned with traps 

12 Fossil cave with spectacular petrified monsters in walls and trilobites and ammonites everywhere. Just another cave for some but may attract collectors gathering fossils for some purpose

d12 Feature Room
1 Crystal cave lit by magic light and may have harmonic, mind-altering, or magic effects. Some guardian, researcher or robber may be here to control and steal crystals. The crystal may have magical effects or summon defenders. Explorers will come here to gather materials despite risks. Chrystal life may be hostile 

2 Forest cave with growing and crawling life, may be fungal or have magical lighting and surface world plants. Various creatures will lair here, but it will also attract giant ambush predators and hunters from some faction. Besides food there are magical resources may grow here or unique species. May have fey beings of darkness or spirits who protect it from abuse

3 Lake cave has a vast body of water with at least one rocky island. May be crystal clear or black or green, depending on purity. Blind and luminous fish or invertebrates live in the water. A large marine creature will use this as a lair and may be visited by aquatic humanoids or underground people for supply or ritual purposes. Various creatures come here to drink or reproduce (giant tadpoles!)

4 Temple cave of an ancient underland religion or cult. Had idols, wall art, an altar and stone braziers and possibly cursed treasures. Often has a dangerous guardian or even a cult here performing rituals. Likely to be some hideous alien bastards here but not here for a rejuvenating herbal tea and to cleanse their auras
5 Stronghold cave with a fortified structure like a tower or bridge. Some subterranean folk made this as a bastion or to hold a choke point. May have access to other passages into the deep. May be abandoned and adopted as a monster lair or with undead. Often occupied by underground militaristic faction with guard beasts or a spell slinger

6 Lava cave with a lava pit or river passing through. May be home of a fire beast like salamanders but fire cults or some heat loving humanoids might live here and use as a home base by following lava and vents humans probably cant. May have gems or mineral wealth and may be some crude religious shrine

7 Cathedral cave with awesome vaulted ceiling with spectacular mineral formations and prehistoric or prehuman cave art. May be used as a camp place for travellers or a faction. May be used for rituals by an underland faction

8 Petrified Forest with stone tree trunks and other petrified life from primordial times or from the end of the age of darkness, when many dark creatures died and became stone when the new sun ended that age and buried them. There are magics that can restore life of these beings so wizards or cultists come here to recover long-lost species 

9 Sleepers' cave with sleeping prehuman beings sleeping for some future apocalypse. Giants and other titanic monsters may be in a magical slumber and beings avoid waking them. It might be possible to feed from them or tap their blood. Other beings of prehuman black wizardry may well sleep in crystal sarcophagi or blocks of magic ice. There may be guardians or cultists here but so far nothing for aeons has changed here. There may be stone writing, or magical lanterns or even a shrine here that might control the room 

10 Ancient plaza ruin where prehistoric beings traded and perhaps factions of the deep still do. It's a good place for goblin or troll markets. A faction control the outpost charging fees and executing troublemakers. It may operate more like a crime guild with a boss and enforcers. Long-abandoned, empty ones might have a concealed predator lurking in this seemingly quiet place
11 Spawn pit where a bubbling living lake of liquid flesh with eyes and limbs spawns mostly pathetic, unique mutant creatures who eat each other or luminous moss and bugs. Visitors may be on the menu. Mutant chaos cults may come here to drink from mutagenic puddles for possible new powers or crippling problems. Wizards and alchemists desire samples to create monsters. Worshipers of the lake may be here, throwing victims into the living mass. The lake is some protoplasmic deity and may be leaking in here from some other plane. May be fleshy or glowing or just slime. Oozes and gelatinous creatures might roam here too.  

12 Deep Gate a fortified tunnel to the deep. An ancient millitary faction built it and still may. They might have been replaced several times over the ages or perhaps their servants or pets or devolved descendants rule now. The main gate will be very heavy and the mechanism may require work. A magical leader will rule and demand that strangers present their passports or credentials or just demand a toll. They might also be hungry