Fungal forest

A cavern filled with fungi taller than a man: pale stalks, caps as wide as tables, shelves of bracket fungus up the walls, and underfoot a carpet of mould that swallows every sound. Some of them glow a faint green or blue, enough to see shapes but not colours, and the air is warm, wet and smells of cellar and mushroom soup. Blind beetles, slugs and the things that eat them live in the litter, and the fungi themselves are not always harmless. The folk of the depths come here to farm and to gather, much as people once grew mushrooms in the old quarries under Paris, and they keep to the paths they know.

Light
Dim
Going
Slow

Going down

How warm the rock is and whether this place can grow there, under a temperate land: the deeper, the hotter.

Near the surface (50 m)
11 °C, it grows
A few hundred metres down (400 m)
21 °C, it grows
A kilometre down (1 km)
38 °C, nothing of it grows (too hot)

Hear it

Hazards

  • Spore puff. A swollen cap bursts underfoot and a brown cloud hangs in the still air. It tastes of earth, then the throat closes. D&D 5e (House rule): Our rule: each creature within 3 m (10 ft) of the burst cap makes a DC 12 Constitution save or has the Poisoned condition for 1 hour, coughing too hard to stay quiet. A DC 13 Intelligence (Nature) or Wisdom (Survival) check spots the ripe caps before anyone treads on them.
  • Rotten floor. Fallen stalks and mould have roofed over a crack in the cavern floor. The crust holds one step, then gives. D&D 5e: The creature falls 3 to 6 m (10 to 20 ft), taking 1d6 Bludgeoning damage for every 3 m (10 ft) it falls, and lands Prone unless it took no damage. Our addition: a DC 13 Wisdom (Perception) check notices the floor sagging first.
  • Fungus light. The glow of the caps is enough to walk by, not enough to see what moves between the stalks. D&D 5e: Where the fungi glow, the forest is in Dim Light and Lightly Obscured: Wisdom (Perception) checks that rely on sight have Disadvantage. Away from them it is Darkness.
  • The wrong mushroom. Half of what grows here is food and the other half looks just like it. D&D 5e (House rule): Our rule: a creature that eats a mushroom it does not know makes a DC 13 Constitution save. On a failure it has the Poisoned condition for 1d4 hours and, for the first hour, sees things that are not there. A DC 12 Intelligence (Nature) or Wisdom (Survival) check tells the good from the bad before eating.

Adventure hooks

  1. The mushroom farmers of the depths have found a new cap growing in their best row, purple and warm to the touch, and every slug in the cavern is crawling toward it. The headwoman wants it cut down; her son has already tasted it.
  2. A cook from the surface pays a fortune for one particular glowing mushroom that makes any stew taste of roast meat. The pickers who know where it grows also know what else feeds on it.
  3. In a ring of bare ground where nothing grows, the party finds a lantern still burning beside a sleeping traveller wrapped in white threads. He wakes up cheerful, and he has been asleep for a very long time.
  4. Two farming families of the deep share the cavern by an old line of stones, and someone has been moving the stones a little each night. Both families blame each other; the stones are being moved by the fungus itself.

What may happen

  1. Straight rows of white caps on beds of dung and straw, and a little stone hut. Someone tends this field, and is not far.
  2. Spores drift down from the high caps like slow snow and settle on packs and shoulders.
  3. Somewhere ahead a mushroom starts to scream. Everything that hunts here now knows where to look.
  4. A line of glowing caps, each one snapped off at the stalk: someone has been marking a trail.
  5. A slug as long as a cart lies across the path, eating its way through a stalk. It is in no hurry.
  6. A perfect ring of caps around a bare patch of floor. Nothing grows in the middle, and nothing walks across it.
  7. A body under a blanket of mould, so overgrown that only the boots show. Its pack is still on its back.
  8. Small grey figures with baskets cut caps and lay them in rows. All at once they stop and turn to look.
  9. A heap of rotting caps steams in a cold side passage, warm as a compost heap. Something has slept against it.
  10. Webs stretch between the tallest caps, grey with spores and heavy with dry husks.
  11. A rotten stalk gives with a long groan, and a cap the size of a table comes down across the path.
  12. Clean water drips into a cap that has grown like a bowl. Someone has left a cup beside it.
  13. A lantern hangs from a stalk, still lit, with no one near it.

Creatures

A town here

A city can live down here, fed by what grows below. Build it in Hearth

To bring back

Mycelium, Myconid Spores, Bat Guano, Brutacian Lung, Bugbear Tooth, Deep Gnome Nose, Fire Beetle Glands, Obsidian Powder, Ooze Portion, 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, Drow Hair, 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, Phase Beast Heart, Ruby Powder, Sapphire Powder, Selenite Sliver, Native Sulfur Crystal, Tanzanite Powder, Young Dragon Tonsils, Zircon Powder, Ankheg Antennae, Barghest Fang, Basilisk Throat, Cranium Rat Brain, Cyclops Eye, Drider Tongue, Flumph Hypothalamus, Grell Beak, Kuo-Toa Gill, Mind Flayer Brain, Minotaur Heart, Ogre Liver, Phase Spider Egg, Troll Bone Marrow, Beholder Eye, Deep Lantern Organ, Dragon Tonsils, Gorgon Muzzle, Oblex Slime, Oni Liver, Roper Bile, Shadow Mastodont Eye, Tainted Quaggoth Soul, Aboleth Eye, Adamantine Dragon Tonsils, Alhoon Brain, Amethyst Dragon Tonsils, Iridium Powder, Elder Oblex Slime, Purple Worm Bile, Sapphire Dragon Tonsils, Shadow Dragon Gland, Tarrasque Carapace Piece, Topaz Dragon Tonsils, Tungsten Powder, Wyvern Poison

Elsewhere below

Doline jungle, Glowing meadow, Bare labyrinth, Lava tubes, Sulphur cave, Crystal caverns, The abyss

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.

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