A d100 list of found objects, unexpected sights, and strange encounters for your players to come across while exploring the tunnels left behind by lava flows.
Smooth stone belies the volcanic fury that carved these tunnels.
Volcanic eruptions can be a force of creation as well as destruction. Under the right conditions, lava flows can form crusts as they cool; said crust then becomes the ceiling of a lava tube cave, defined by smooth, pahoehoe floors and ridged walls from differing lava flow depths as the tunnels drained. Closer to the site of eruption, lava tubes turn into larger tunnels carved by deep lava rivers that crusted over. Farther out, branching lava tubes and wider caverns emerge as the flow bursts through the cooling walls.
Your adventurers may find themselves falling through a deteriorated lava tube ceiling, hunting monsters that have made their homes in the tunnels, or they may be following the tunnels to reach the heart of a dormant volcano. Regardless of how they arrive, the party finds danger and frightening beauty in these volcanic caves.
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. A portion of chipped cave wall. The marks look like they could have been made by claws or pickaxes.
2. A voice saying, “You’re almost there!” in Common echoes through the cave. No matter how hard the party looks, they cannot find the source.
3. A skeleton with 100 feet of rope and climbing pitons beside it.
4. A colony of unknown spiders. They appear to be blind, adapted to life in these tunnels.
5. A narrow section of the tunnel, three feet wide and fifteen feet long, that characters must pass through one at a time. Characters must make a Wisdom saving throw while moving through or become overwhelmed by claustrophobia on a failed save. Even characters that are not claustrophobic must make a Wisdom save.
6. A sword is stuck into the cave wall. No matter how hard characters try, they are unable to pull it out. Mysterious magics flicker in the air.
7. A thin crust of red crystals lines the ceiling.
8. Lavacicles hang like shark teeth from the ceiling.
9. The party stumbles upon a campsite that appears to have been recently used, but no other trail or trace of a living thing is nearby.
10. [Encounter] A gelatinous cube lies in wait for the party.
11. Three lava pillars have formed in this section of the tunnel. Upon closer inspection, it almost looks like there are faces in them, twisted in agony and silent screams. Breaking into the pillars reveals that they are hollow, with each holding a humanoid corpse.
12. Tree roots puncture the ceiling. A spelunker’s satchel is half-hidden amongst them. Inside are a half-finished map of the tunnels, charcoal, some moldy rations, and an amethyst.
13. Hundreds of miniscule holes line the floor, walls, and ceiling of this section of the caves. A low squirming sound can be heard coming from them, but there does not appear to be anything inside.
14. A mutilated corpse. The cuts and gashes on its body seem precise and surgical. Some of its organs are missing.
15. A smaller tunnel branches off from this one into a nearly perfect, spherical cavern. An altar of obsidian stands in the center. Touching the altar grants a character a vision of their death in these tunnels. They have disadvantage on death saving throws until they leave the caves.
16. A portion of the ceiling has collapsed, letting in light from the surface. Or it is collapsing as the party travels under it.
17. A pond has formed from water dripping into the caves. It is safe to drink, but tastes of minerals and iron.
18. A battered wooden mask carved to look like an eyeless bear face.
19. A backpack containing a water canteen, snapped pickaxe, and a tattered book of decadent poems.
20. A wooden door set in the wall has a sign next to it that reads “Tatter’s Tavern”. Inside, a small tavern has been hewn from the stone, with stone tables, counters, and chairs. Tatter, a male gnome, tends the bar. Once the party finishes and leaves, the door vanishes, replaced by stone again.
21. A section of the tunnel wall appears darker than the rest. It feels squishy to the touch.
22. A swarm of four-winged bats are asleep on the cave’s ceiling.
23. The haunting echo of laughter can be heard for a brief moment by one character. The others do not hear anything.
24. Stalactites of a type of crystal (DM’s choice) hang from the cave ceiling.
25. [Encounter] The characters can hear a dull beating in the cave wall. It almost sounds like a heartbeat. It is really the sound of a bulette on the prowl, burrowing after them.
26. A small wood carving of a lizard with a saddle.
27. A crystal flute that causes any other crystal in a 30-foot-radius sphere to resonate with the same note played.
28. A skeleton that has melded with the stone floor, as if the ground were slowly absorbing it.
29. Cave paintings of a mythic beast that seem to shift slightly whenever characters are not looking at them.
30. Gormrun, a crazed human clothed in rags, is carrying around a rickety cart with different cave-themed goods. He has stone/crystal weapons, potions made from minerals and animal bones, as well as uncommon and rare magic gems. He will only accept stories of the world above as payment, though he does not wish to leave the caves.
31. A child’s blanket covered in rubble.
32. A hole in the cave floor. It can already be there when the party arrives, or it could open under a party member.
33. One party member begins to feel as though they are being followed, but never manages to catch sight of their pursuer.
34. A half-burned journal from a spelunker who got lost in the tunnels. It has bite marks.
35. [Encounter] The party takes a wrong turn and ends up in a larger pocket of the caves facing a crystal dragon. Age and crystal type are up to the DM.
36. An albino snake wrapped around the hilt of a rusty sword.
37. A group of ghostly miners, chanting a work song. They disappear if the party members get too close to them.
38. The skull of a cyclops fills the cavern ahead. The party has to clamber through its mouth or sightless eye socket to continue down the passage.
39. A crystal tree grows down from the ceiling of the cavern.
40. A set of stairs have been cut out of the stone wall, twisting downward in a spiral. At the bottom is a circular room with a glowing subterranean garden. Taking a short rest in the garden grants the benefits of a long rest instead, but harming any of the plants causes the garden’s guardian to animate and attack.
41. A lifelike statue made of different stone than the cave. It’s almost too lifelike.
42. Purple, shimmering fluid in a glass bottle.
43. A broken wagon with a tattered cloak, rotting apples, and an empty flask scattered about.
44. A rusted longsword with a broken hilt. It looks like it has not been touched in decades.
45. [Encounter] A lone dvergr has lost their way in the tunnels and ask if the party can help them find their way back. If the party agrees, they lead the party into a dvergr ambush.
46. A corpse with various fungi growing from it. They look edible.
47. A statue of a forgotten deity carved out of the tunnel wall. A recent sacrifice lies at its base.
48. A Medium-sized stone seems to be following the party. It appears at the same distance behind them whenever no one is looking at it. It will only stop if someone walks backwards, staring at it until it is completely out of sight.
49. A necklace with a dragonfly pendant, forged from silver.
50. [Encounter] A pair of basilisks appear in the tunnel ahead!
51. The floor of the cave wavers, as if something were swimming through the stone underfoot.
52. A bear cub. Its mother might be nearby, or it might be lost and need help finding her.
53. A rusted dagger. Tied to its hilt is a bright green scarf.
54. The shed skin of a very, very large snake.
55. A humanoid face appears in the stone wall. It screams at the party, proclaiming that doom is upon them. Any character that responds to it becomes blinded for a full minute. The face vanishes after it blinds at least one character, or after ten minutes if no one responds to its threats.
56. A dusky red clay pitcher of mead. It refills itself at the start of every day.
57. The sound of chattering teeth grows louder and louder. At first it is impossible to tell where it is coming from, but eventually the party realizes that one of them is making the sound. They can choose to stop once they realize it.
58. A crate full of precious gems. They transform into dull quartz when removed from the cave.
59. A lute with a broken string. The initials, E. C. are carved into it.
60. [Encounter] A swarm of bats approaches. As they get closer, they coalesce into a single giant bat. When defeated, the corpse turns into runny, bloody mud.
61. A deep blue sapphire is lodged into the floor. It takes an hour to remove it, even with the right tools. The cave shudders once the gem is removed.
62. A hole in the wall, large enough for a hand to fit inside. Soft murmuring can be heard from it. Nothing is inside.
63. A cluster of skulls hangs from the ceiling on strands of spider web.
64. Three arm bones arranged in the shape of a star. They don’t appear to be held together by anything but can’t be pried apart with either force or mundane magics.
65. [Encounter] This tunnel dead-ends in a large, circular cave with a field of statues. They are the creations of the stone giant living here. The giant is mistrusting of humanoids, but peaceful, preferring art to war. They will not harm the party as long as their statues remain unharmed.
66. A burned out torch still in the grip of a severed hand.
67. A golden ring next to a wall. When worn, it allows a creature to move through stone as if it were not there. The enchantment does not apply to the ring itself, however.
68. A large barrel. Inside are rotting herring and a strange glass orb.
69. A massive lava pillar nearly blocks the passage ahead. If the players dig into it, they find it to be hollow and large enough for all of them to rest inside.
70. [Encounter] The party finds a hammer lodged in an obsidian stone. If a character removes the hammer, the stone transforms into an earth elemental that attacks. The elemental will revert to its stone form if a character returns the hammer. The hammer is not magical, the earth elemental just really likes that specific hammer.
71. The start of a sentence is carved into the wall. If a character tries to read it as they travel, they will instantly find themselves at the end of it, having traveled a full mile.
72. A pair of travelling boots…on the ceiling.
73. A spider inside of a clear crystal. The spider still seems to be alive and watching.
74. A chipped shovel with a broken handle.
75. An elderly, dweorg woman who says that she is the queen of an ancient dweorg empire. She sadly cannot remember the name of it, where it was, or how she ended up in these tunnels. She vanishes a moment later.
76. The smell of sulfur becomes overwhelming for a moment.
77. A totem to some unknown god, constructed from bones of unknown creatures.
78. Jagged spires of kyanite jut from the floor, ceiling, and walls.
79. Dead insects coat the floor for the next half-mile.
80. [Encounter] A cloaker has been stalking the party for a while and is finally ready to pick off any stragglers.
81. A walking stick with strange spirals carved into the haft.
82. The remnants of a massive egg. Whatever was inside hatched, recently by the look of it.
83. A keg of ale. It tastes slightly metallic. Anyone who drinks it hears the crash and clatter of a massive battle for half an hour afterwards, effectively deafening them.
84. Three holes are arranged in a triangle on the wall. They are only large enough for a finger. Sticking a finger in each hole creates a fourth in the center. A tiny gust of stale wind comes out of the center hole. Nothing else happens.
85. A bell hangs from the ceiling by a string. It is cursed. Anyone who hears its sound becomes afflicted by a madness for an hour. If anyone touches it, they attune to it and become mad permanently. If an attuned creature rings the bell within earshot of another creature though, they steal that creature’s ability to understand language for an hour if the creature fails a Charisma saving throw.
86. A stone is skipped along the floor past the party. They cannot manage to find any trace of who threw it.
87. A trail of unspooled yarn. One end of it appears to have been cut off.
88. A thin crust of salt coats the floor, crackling underfoot.
89. A severed foot. It has been unnaturally dried and preserved.
90. [Encounter] A drow hunting party emerges from a side tunnel. Their grins of cold malice flash in the dark before they attack.
91. A stone fountain is carved into the wall. It is filled with stagnant, putrid water.
92. The scent of cooking meat comes from up ahead. The source is a blood-red stone.
93. An ancient cave painting of adventurers walking through the tunnels. They look unnervingly like the party members.
94. The fangs of some large beast, dug into the stone floor.
95. The party comes across an intersection made of black, reflective obsidian. There are ten different tunnels to choose from. However, the only correct path is the one they immediately come from. If they take any other path, they will end up back at the intersection after a short time, with the lowest cost item in their inventory having vanished. This happens every time they pick an incorrect path.
96. A set of footprints. They are sunken into the stone.
97. A rusty spear stuck into the wall. A message tied to the haft says, “whoever reads this will die”. The message rings true.
98. The sound of rain can be heard tapping on the cave ceiling. Water finds its way through a crack and pools along the floor.
99. A golden ring that has been shaped to look like a centipede.
100. [Encounter] A young demonic cultist is preparing to raise a pit fiend. He doesn’t know that the ritual he is preparing for is fake (unless the DM decides it isn’t).