Toxic Cave

Cave
Dave Bunnell / Under Earth Images, CC BY-SA 2.5, Wikimedia Commons

The land itself is poisoned. Yellow water stands in the hollows, the air stings the eyes, and the few plants that still grow are bitter and oddly coloured. Whatever lives here has learned to live with poison, or carries it. Hollows in the rock, from a shelter under a ledge to networks that run for kilometres. Dark, cool and the same temperature all year, home to bats and pale creatures, and to whatever people bring or hide there.

Hear it

For the table

Ground
hard going, about 10 km a day on foot
Water
by season
Foraging
nothing

Hazards

  • Darkness. No daylight at all: every step needs a light, and every light burns out. A party without spare torches or oil is blind.
  • Getting lost. Under the trees, in the dunes or in the dark, every direction looks alike. Without a guide or a sure landmark, a party walks in circles.
  • Falling rock. Frost, rain or a careless step bring stones down from above. Scree slides underfoot.
  • Rising water. Rain outside fills passages within hours. A way in can become a sump.
  • Poisoned water. Springs and pools look clear and taste of metal. Boiling does not clean them.
  • Choking vapours. In still hollows the vapours pool, heavy and unseen. Birds that land there do not fly off again.
  • Caustic mud. Some patches of mud bubble and smoke. They eat through leather in an hour, and through skin faster.

D&D 5e

Plays as
Underdark, normal pace at most
Checks
forage: Survival DC 20 · find the way: DC 10 · search: DC 20
Creatures are spotted at
2d6 × 10 ft
  • Darkness. Darkness is Heavily Obscured: a creature trying to see into it is Blinded. Dim light is Lightly Obscured. Darkvision turns darkness into dim light within its range, in shades of grey.
  • Poisoned water. (House rule) A creature that drinks the land’s water, boiled or not, makes a DC 13 Constitution save or has the Poisoned condition for 24 hours. Only water carried in, or made pure by magic, is safe.
  • Choking vapours. A creature in the vapours must hold its breath, for 1 plus its Constitution modifier minutes (never less than 30 seconds). After that it gains 1 Exhaustion level at the end of each of its turns, and loses them all as soon as it can breathe again.
  • Caustic mud. (House rule) A DC 13 Wisdom (Survival) check spots a patch before anyone steps in. A creature that steps in makes a DC 12 Dexterity save or takes 2d6 Acid damage, and its boots are ruined.

This work includes material from the System Reference Document 5.2.1 ("SRD 5.2.1") by Wizards of the Coast LLC, available at https://www.dndbeyond.com/srd. The SRD 5.2.1 is licensed under the Creative Commons Attribution 4.0 International License, available at https://creativecommons.org/licenses/by/4.0/legalcode.

Pathfinder Second Edition

Plays as (Pathfinder Second Edition)
underground, difficult terrain, about 16 km a day at Speed 25
Checks
Subsist: Survival DC 30 · Sense Direction: Survival DC 20
  • Getting lost. Sense Direction (Player Core p. 246): a Survival check once a day, –2 without a compass; DC 15 in ordinary wild land, 20 in deep forest or underground, 30 in a featureless desert. Getting lost has no fixed penalty: the GM decides where the party ends up.
  • Falling rock. An avalanche, landslide or collapse deals major or massive bludgeoning damage (8d6 to 24d6); a Reflex success halves it and a critical success also avoids burial. Buried creatures take minor damage each minute and are dug out with Athletics (GM Core p. 96).

This product is licensed under the ORC License located at the Library of Congress at TX 9-307-067 and available online at various locations including paizo.com/orclicense, azoralaw.com/orclicense, and others. All warranties are disclaimed as set forth therein. Attribution: this rules layer is based on the following Licensed Material: Pathfinder Player Core © 2023 Paizo Inc., Designed by Logan Bonner, Jason Bulmahn, Stephen Radney-MacFarland, and Mark Seifter. Authors: Alexander Augunas, Kate Baker, Logan Bonner, Jason Bulmahn, Carlos Cabrera, Calder CaDavid, James Case, Eleanor Ferron, Steven Hammond, Joan Hong, Vanessa Hoskins, James Jacobs, Jenny Jarzabski, Erik Keith, Dustin Knight, Lyz Liddell, Luis Loza, Patchen Mortimer, Dennis Muldoon, Stephen Radney-MacFarland, Mikhail Rekun, David N. Ross, Michael Sayre, Mark Seifter, Kendra Leigh Speedling, Mark Thompson, Clark Valentine, Andrew White, Landon Winkler, and Linda Zayas-Palmer; Pathfinder GM Core © 2023 Paizo Inc., Designed by Logan Bonner and Mark Seifter. Authors: Amirali Attar Olyaee, Logan Bonner, Creighton Broadhurst, Jason Bulmahn, James Case, Jesse Decker, Eleanor Ferron, Fabby Garza Marroquín, Jaym Gates, Matthew Goetz, James Jacobs, Brian R. James, Jenny Jarzabski, Dustin Knight, Jason LeMaitre, Lyz Liddell, Luis Loza, Ron Lundeen, Stephen Radney-MacFarland, David N. Ross, Michael Sayre, Mark Seifter, Owen K.C. Stephens, Amber Stewart, Clark Valentine, Landon Winkler, and Linda Zayas-Palmer; Pathfinder Monster Core © 2024 Paizo Inc., Authors: Alexander Augunas, Dennis Baker, Kate Baker, Joshua Birdsong, Joseph Blomquist, Logan Bonner, Jason Bulmahn, James Case, John Compton, Paris Crenshaw, Adam Daigle, Darrin Drader, Brian Duckwitz, Robert N. Emerson, Scott Fernandez, Eleanor Ferron, Leo Glass, Matthew Goodall, BJ Hensley, Thurston Hillman, Vanessa Hoskins, James Jacobs, Jenny Jarzabski, Miko Kallio, Jason Keeley, Jeff Lee, Lyz Liddell, Luis Loza, Ron Lundeen, Robert G. McCreary, Philippe-Antoine Menard, Jacob W. Michaels, Dave Nelson, Jason Nelson, Tim Nightengale, Stephen Radney-MacFarland, Mikhail Rekun, Patrick Renie, Alex Riggs, David N. Ross, Michael Sayre, Mark Seifter, Chris S. Sims, Amber Stewart, Jeffrey Swank, William Thompson, Jason Tondro, Clark Valentine, Landon Winkler, Tonya Woldridge, and Linda Zayas-Palmer. If you use our Licensed Material in your own published work, please credit us as follows: Biomes, Pathfinder Second Edition rules layer © 2026 Michael Ghelfi. Reserved Material: the names of Biomes and its catalogues, its descriptions, sounds, art and code. Pathfinder is a registered trademark of Paizo Inc.; this site is not published, endorsed, or specifically approved by Paizo Inc.

A scene

  • Simple Cave. The cave murmurs and sighs. A slow, cycling breath that carries no warmth and no explanation. Deeper within, water chooses to occasionally drip. The dark is total beyond the reach of any flame. Somewhere above, or perhaps below, something shifts in the stone. This cave is not empty. It is never empty. And it is never full. The full generator on the blog

Adventure hooks

  1. A herbalist has lived thirty years in the poisoned land in perfect health, and she sells a tonic she swears is the reason. The tonic is pond water: she is well because she has swallowed a little poison every day of her life, and now she wants to move to town to meet her grandchildren.
  2. A lord has heard that the poison yields the finest yellow dye in the kingdom and has sent his steward to fetch a barrel of it. The steward is terrified, unfailingly polite, and under orders not to come home with less than a full barrel.
  3. The poison spreads a mile further every year, and it has a source: for a century the alchemists of the nearest town have buried their failed brews here. Their new mistress did not know, and now that she does, she has decided it would be cheaper to make sure nobody else ever finds out.
  4. A boy from the edge of the poisoned land has tamed one of its creatures, small, bright and deadly to touch, and his father wants it killed. It has saved the boy’s life twice already, and the water it drinks from runs clear for a day afterwards.
  5. A shepherd’s dog chased a fox into a crack in the hillside and came back carrying the jaw of a cave bear. The shepherd wants the crack walled up; his son wants to see the rest of the bear.
  6. The bats have stopped leaving their cave at dusk. The guano diggers who sell the droppings to farmers are out of work, and something deep in the cave is keeping the bats in.
  7. Animals painted thousands of years ago cover the walls of a deep chamber. An old woman who lives at the cave mouth adds a new one every spring, in the same hand, and will not say who taught her.
  8. The town ages its cheeses in a cool cave, and the cheeses have started to disappear. Whoever takes them leaves coins in exchange, fair payment, minted by a king nobody has heard of.

Animals

Creatures

Also met here

This work includes material from the System Reference Document 5.2.1 ("SRD 5.2.1") by Wizards of the Coast LLC, available at https://www.dndbeyond.com/srd. The SRD 5.2.1 is licensed under the Creative Commons Attribution 4.0 International License, available at https://creativecommons.org/licenses/by/4.0/legalcode.

To gather

Ooze Portion, Bat Guano, Brutacian Lung, Bugbear Tooth, Deep Gnome Nose, Fire Beetle Glands, Obsidian Powder, Scorpion Venom, Sulfur Pinch, Topaz Powder, Tourmaline Powder, Troglodyte Thumb Nail, Amber Tears, Amethyst Powder, Aquamarine Powder, Black Powder, Bloodstone Powder, Chalcedony Powder, Chitine Silk, Cockatrice Liver, Crystal Powder, Echo in Stone, Ettercap Mandible, Ettin Toe, Firenewt Bile, Fixed Nitre, Galeb Duhr Soul, Giant Spider Perfect Eye, Jade Powder, Jasper Powder, Jet Powder, Lapis Lazuli Powder, Magnetite Shavings, Malachite Powder, Moonstone Powder, Myconid Spores, Phase Beast Heart, Ruby Powder, Sapphire Powder, Selenite Sliver, Native Sulfur Crystal, Tanzanite Powder, Young Dragon Tonsils, Zircon Powder, Ankheg Antennae, Basilisk Throat, Cyclops Eye, Drider Tongue, Flumph Hypothalamus, Grell Beak, Minotaur Heart, Ogre Liver, Phase Spider Egg, Troll Bone Marrow, Dragon Tonsils, Gorgon Muzzle, Roper Bile, Shadow Mastodont Eye, Adamantine Dragon Tonsils, Amethyst Dragon Tonsils, Iridium Powder, Purple Worm Bile, Sapphire Dragon Tonsils, Shadow Dragon Gland, Topaz Dragon Tonsils, Tungsten Powder, Wyvern Poison

The same milieu, otherwise

Cave, Cursed Cave, Blessed Cave, Corrupted Cave, Haunted Cave, Crystalline Cave, Fungal Cave, Enchanted Cave, Primeval Cave, Eldritch Cave, Frozen Cave, Burning Cave

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