A d100 list of found objects, unexpected sights, and strange encounters for your players to experience while venturing through winding, eroded caverns.
Rushing rivers and streams gouge narrow passages into dark, stony depths.
While it may take years, decades, or even millennia, rivers and streams can carve passages in the earth. The erosional force of water, along with abrasive sediment and debris carried by it, cuts through weaker pockets in the stone. This original fissure widens and burrows deeper as the water continues to flow. Corrasional or erosional caves are formed around flowing water and tend to be more twisting and narrower than other cave types as a result. However, caves formed by other processes can become corrasional or erosional caves when a stream or river finds its way into the system and begins a new phase of enlargement.
Access to running water makes these caves desirable homes for the large variety of Underdark creatures and civilizations. Where other caves might have a few solitary monsters or spelunkers, erosional caves can support large Underdark communities. Your party could be hunting for the ancient treasure of an Underdark empire, on a mission to rescue some newly abducted slaves for a drow city, or attempting to find the last of a rare, extinct species.
When using this list, feel free to choose any options you particularly like. You can also let fate decide and roll a d100. Every fifth option in the list is more consequential than the rest, so roll a d20 and multiply by 5 if you want to ensure a truly unique encounter for your party.
1. An abandoned minecart. It contains a severed foot, a lantern, and sack full of rations (6 units of stock).
2. A silver amulet with a spider-shaped pendant.
3. A bat descends on the party, shouting “The walls aren’t real” before flapping away.
4. The party sees two boulders up ahead. Once they have passed them, looking back, there is only one.
5. A very obvious pit trap sits in the center of the tunnel. Moldy planks cover the hole along with some rubble. This pit trap is meant to distract from the other, better concealed pit traps to either side of it.
6. The remains of a dvergr hunting party. The corpses are strewn about and seem to have been mauled by a large beast.
7. A chandelier hangs from the ceiling. It is lit, but there are no signs of any other living beings in the vicinity.
8. A large, leather tarp covers a portion of the cave wall. Underneath, the front of a house has been carved out of the stone.
9. A porcelain teapot and teacups are arranged in a small circle. They are in pristine condition and filled with steaming tea.
10. [Encounter] A pair of trolls, Froth and Groth, are bickering. Froth believes that Groth ate its last dwarf, but Groth protests that Froth ate them already and just forgot about.
11. A large tree with pale bark and dark leaves grows beside a river. A smattering of desiccated animal corpses lie around its base.
12. The path ahead is covered in thick, strong spider webs. The faint sound of skittering can be heard coming from within the walls.
13. One party member sees a glowing, humanoid form out of the corner of their eyes. When they turn to get a better look, it vanishes.
14. An old campsite. There is a pack containing rotten fruit (1 unit of stock, carries a disease) and a bundle of arrows.
15. The party encounters a dweorg town. The houses have been carved from the stone. The dweorg are currently celebrating a local holiday that involves copious drinking and singing. They invite the party to join.
16. A large, perfectly rounded tunnel branches off from the main path. It ends abruptly in a flat stone wall that emits a continuous, soft whispering in an antediluvian language.
17. A pile of fresh animal scat. A very, very large pile.
18. A natural bridge has formed over a stream. While standing on it, characters hear a voice say “vile dark” in Elvish.
19. A cluster of thick grass and orange flowers lines a river. The flowers smell like beeswax.
20. [Encounter] A flumph appears, glowing with bright distress. It tries to get the party to follow it to a recent cave in, where another flumph has been trapped by fallen rocks.
21. A cluster of vines have grown in and around a giant’s skull.
22. The remnants of an old dwarven mining town. The echo of pickaxes on stone can still be heard occasionally, despite there being no signs of life.
23. An iron horseshoe inlaid with small, glittering amethysts.24. A patch of glowing mushrooms.
25. [Encounter] A band of drow outriders and drider is returning from a successful slave raid. They have several prisoners with them (DM decides number of enemies based on party level).
26. A vial of blue blood. It is unclear what it has come from. Uncorking the vial turns the blood red.27. An albino species of deer. It is blind and has antlers that curve downard.
28. Humanoid skulls set into the walls at regular intervals for the next half-mile.
29. A rat clad in a tiny set of bone armor. The armor seems to have been made from the skeleton of a cat.
30. [Encounter] A grumpy svirfneblin stonespeaker/sorcerer. He has a number of earthen-themed spells but will only fight the party if provoked.
31. A nest of sparrows. Their feathers are an ashen gray, and their forms seem to waver as if they were made of smoke.
32. A wooden ladder. Climbing to the top reveals a small hole in the ceiling. If a character reaches inside, they find a dagger with a blade made of ruby.
33. The remnants of a large number of campfires and tents. From the scattered webs it seems likely that this is the campsite of a massive drow military force.
34. A mushroom garden. There are no signs of a gardener, but the mushrooms are carefully organized by species in orderly rows.
35. A pair of dirty socks. They are cursed. Anyone who wears both socks simultaneously develops a deathly fear of water.
36. A sign carved into the cave wall says in Undercommon “Beware! The Fluggle Grump waits ahead!”
37. A glass bottle with a few twigs and an empty butterfly chrysalis inside. There appears to be an acid-burned hole in the glass.
38. An altar to an old, forgotten god. A skeleton is frozen in prayer position before it.
39. A silver scarab beetle. It gives off warmth and the quiet sound of chittering.
40. [Encounter] A couple of dweorg in bloody rags coming from the opposite direction. They run past the party as a minotaur emerges from the dark in pursuit.
41. A spectral elf appears, clothed in rich robes and wearing a jagged crown on their head. They mutter unintelligibly. If the party tries to interact with them, they look at the party with shock and scream “the children!” in Elvish before vanishing.
42. A rabbit with eight legs clambers by on the ceiling. It has gray fur and eight eyes as well.
43. The party notices that the echoes of their voices sound less like them and more like a gloomy child mimicking their words.
44. A family of goats with mushrooms and algae growing on their bodies.
45. Four human spelunkers have made camp. They are cheerful and invite the party to share some food and spend the night with them. When the party wakes in the morning, they find themselves sleeping beside four skeletons instead.
46. A humanoid skeleton made entirely out of quartz. It is in a sitting position near a river with its toes in the current.
47. A zwerc town. Dozens of incredibly lifelike statues of zwerc are scattered around the village. Their faces are contorted in expressions of surprise, terror, and confusion.
48. A toy wooden ship is sailing down a stream near the party. A rolled-up note in Undercommon is stuck to it. The note reads “Don’t get your hopes up”.
49. A candle made of burgundy wax sits in a small recessed shelf in the rock wall. If a character lights it, a tattoo of the candle appears on their body somewhere. [DM’s choice]
50. [Encounter] A pair of darkmantles hide on the ceiling, ready to drop on two unlucky party members.
51. A nest of snakes. Clumps of rocks have fused with their skin.
52. A deck of playing cards. Half of the cards are missing. The bottom half.
53. A wooden door set into the stone wall. It looks ancient and is in the shape of a perfect circle. Opening the door reveals the stone wall behind it and nothing else.
54. Three glowing orbs of light can be seen farther down the tunnel. They flash green, then blue, then red, before finally going out.
55. The party comes upon a svirfneblin enclave. It is heavily fortified, but will allow them entrance if they approach. A number of deep gnome traders are inside, offering gemstones, potions, and various kinds of mined materials. The party is constantly watched while inside, followed by guards and eyed warily by the denizens. Subject to the GM’s discretion, the party might even purchase a svirf-slug or some of their fabled svirftech.
56. The petrified trunk of a massive, ancient tree.
57. A swarm of shrimp and squid live in this portion of the river. They have a bland, unappealing taste, but will serve as food if caught.
58. A jagged crystal spire. It emits a faint, metallic ring that increases in volume the closer a character gets.
59. An apple rests on a small stone altar. It is really a rock, carved and painted to be indistinguishable from a real apple.
60. [Encounter] The tunnel opens up into a wide, beautiful cavern filled with a mushroom forest, a small lake, and eerily beautiful rock formations. The party should appreciate this wonder while they can, because it is the grove of a formorian who is in need of new slaves.
61. A party member discovers a new allergy to a specific cave lichen. A rash of pimples and pustules appear on their body. They itch terribly. They fade away when the party leaves the caves.
62. A broken hand crossbow and a shattered mirror.
63. An abandoned wagon pulled by a mule. Several corpses are laid out in the back.
64. A granite staff with the skull of a goat attached.
65. A pale stone fountain carved in the style of dwarven architecture. The water in the fountain appears to be unnaturally clear and pure. Any character that drinks from it gets the benefit of a short rest, but only once per month. If a character imbibes more than once per month, they instead gain a level of exhaustion.
66. A blockage in the stream has created a knee-deep pool of water in the tunnel ahead.
67. The passageway collapses behind the party. Momentary laughter echoes through the stone walls.
68. A brass spoon. It probably wasn’t made for humans though, seeing as it is three-times the size of a normal spoon.
69. Goblinoid tracks. Dozens of them.
70. [Encounter] A brief tremor in the stone wall is all that hints at the burrowing monstrosity preparing to launch an ambush.
71. Luminous, blue flowers grow on interweaving vines that cover the floor of the passageway. A bouquet spreads sheds dim light twice as far as a torch.They wither under direct sunlight and lose their glow.
72. A semi-burned journal. The pages inside are blank, except for the word “Balgurl” spelled out in blood.
73. A circle of bones. If any character steps inside, the bones erupt into green flame. There are no obvious effects otherwise.
74. A patch of lichen and moss made of varying colors. It is slowly creeping across the ceiling of the cave.
75. [Encounter] A wight and their small army of zombies. They don’t attack at first, trying to convince the party that they mean no harm to anyone other than the drow civilization that killed them. In fact, they could use some help assaulting a drow camp just a bit farther down the tunnel (DM can decide if they’re being truthful or not).
76. A large gecko clings to the ceiling, hunting bats and other small animals as prey. It has an unnerving intelligence in its eyes.
77. A silver flower lying on the floor. It has a bloom at either end of its stem.
78. A heavy gust of wind blows through the passage, causing the party to shiver.
79. For the next ten minutes of travel, one party member is overcome by the fear that something is lurking in the shadows on the ceiling. Whenever they look up, however, they see nothing there.
80. A silver coin. It becomes attached to the first character who picks it up. No matter where they put it, throw it, sell it, etc., the coin always ends up back in the palm of their hand after thirty minutes.
81. A bottle with multicolored stones inside.
82. A dead body wrapped up in spiderwebs hangs from the ceiling.
83. A bronze flask. It is empty inside, except for a centipede.
84. A wooden flute held between the teeth of a humanoid skull.
85. [Encounter] A cluster of ochre jellies have had a lot of luck finding food in this tunnel system. And here comes their latest meal.
86. Three stone totems. They are each carved to looked like a different underworld animal; one a spider, one a lizard, and another a bat.
87. A family of badgers. Badgers with six eyes…
88. A rotting hand, clutching a palm-sized emerald.
89. Deep gouges have been torn out of the stone walls. They appear to have been made by long, sharp claws.
90. A rusty shovel. It is cursed. The character who touches the shovel first becomes convinced that there is buried treasure somewhere nearby. If they dig enough holes, then surely, they’ll be able to find it.
91. A series of torches line the passageway ahead. They are held in stone sconces shaped like humanoid hands.
92. A green mask of a devil’s face. It has long curving horns.
93. One of the party member’s name is carved into a wooden sign. The sign points down a narrow branching passage.
94. A dusty old horse brush. It has some horsehairs stuck in its teeth, but also what seems to be chitinous plates.
95. [Encounter] An otyugh that a local drow community is using as a garbage disposal.
96. A lame dog wandering through the tunnels. It seems friendly.
97. Mushrooms have grown around a humanoid-shaped stalactite. It seems to move slightly every time the party takes their eyes off of it. The mushroom-ring seems to slowly close in on the rock whenever the party looks elsewhere.
98. A smattering of blood covers the passageway. It looks like human blood, but it smells faintly of lavender.
99. A group of goblins. A group of dead, dismembered goblins.
100. The lost city of Barmadu. It is densely populated, lively, and home to a large variety of different races. The party can find all sorts of traders, vendors, and merchants here. Of course, the story goes that Barmadu was swallowed by the earth millennia ago, so this can’t be the actual lost city. Right?