25 Underground Cavern Adventure Seeds

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Picture Credit: famalchow

We’re back and we’re getting low with today’s Adventure Seeds as we plumb into the depths of Underground Caverns! These could easily be used in iconic areas such as the Underdark, other underground cavern complexes, or in some cases some might work as a normal cave.

The challenge here was to not make these encounters so much as ways for side plots to open up if they intrigued the party. I also didn’t want to rely on the party having heard rumors in town about the caverns as I imagined most of these would be pretty far below what most would know or hear about.

I didn’t have really any assumptions this time around other than the party is underground in some sort of cave complex with multiple chambers. These could be really underground or near the surface- use your judgement about what works best for your game world!

And lastly, if you enjoy our Adventure Seeds, why not upgrade from 25 to 30? Every time that we post our Adventure Seeds articles we post an additional 5 seeds over at our Patreon as a small way of saying thanks to those who support us!

And now here are the adventure seeds:

  1. Fungal growth completely covers the wall around a passage and upon closer inspection a humanoid face appears in the growth. They tell you to turn back or suffer the same fate as them; becoming a warning for others who dare disturb the fungoids.
  2. An enormous chamber opens up into a seemingly empty city that covers not just the floor but also climbs the wall and the ceiling as well. An orb floats in the center of it all, shedding light and pulsing slightly.
  3. The floor of this cavern is covered in bones of all types and sizes, but different skulls painted in vibrant colors seem to be set in a pattern. Upon closer inspection, the pattern roughly resembles the heraldry belonging to a local noble house.
  4. Whispers can be heard echoing around this chamber of the cavern. They say that if you listen closely, each whisper is what someone’s final words were- or are going to be.
  5. Light emanates out from strange gems embedded in the door of the far wall. Approaching them causes one’s shadow the stretch between the entrance and their position, restraining them as their shadow gets thinner.
  6. A mysterious merchant shrouded in shadow stands near the wall, offering potions or magical fungi for weary adventurers. When threatened or done dealing, they seem to slide into a tiny crevice in the wall.
  7. Two small pools of water sit under a sign that reads “You may ask one question of either” with Don’t Do It scrawled over it. In one pool it shows a young version of the viewer, and the other an elderly version.
  8. Small holes in the cavern wall each have a light of a different color shining through. No clues as to what or why are present other than a single skeletal figure whose arm is stuck in the hole with amber light shining.
  9. Tracks that indicate some sort of struggle end abruptly against a stone wall and then disappear. Approaching the wall gives way to a cold breeze and vibrations make part of the wall appear to shimmer.
  10. Two finely dressed, but long dead bodies sit at a roughly carved table and chairs. Each has a crossbow bolt through their chest, and dusty paperwork full of official seals sits between them on the table.
  11. The end of a long, descending tunnel opens up into a large cavern with a lake and a pirate ship. The ships appears to be rotting and long forgotten, but flickering torchlight from within say otherwise.
  12. Eggs, mostly unhatched and varying from marble sized to a few feet tall, span the length of this room. One of the larger hatched eggs has a lifeless, half-formed humanoid body inside with a name written in elvish on the shell. Further eggs of similar sizes have other names written on them as well.
  13. Metal tracks indicate that this part of the cavern was once used as part of a mine. Zombified humanoids continue to push around and empty out mine carts with nothing in them as well as swing picks at where gems must once have been, going through the motions indefinitely.
  14. A large statue depicting the deities of life and death dueling sits on a dais in the center of this passage. Sparks continuously fly out where their weapons meet, and both sides have what appears to be an area to leave offerings to either deity.
  15. A goblin, startled to have visitors, claims to be an alchemist and asks if anyone is willing and able to get scales from the basilisks who live in another part of the caverns. They say they can unpetrify any who get turned to stone and that the potion the scales are for should make those who drink it impervious to the basilisks’ stare forever.
  16. A rushing waterfall falls through a hole in the center of the ceiling and down a hole in the floor to somewhere below. A choir of angelic sounding words can be heard traveling through the water.
  17. A band of dark gnomes scouting the area for gems are tied up and motion however they can for help. When asked what happened, they say that the dark dwarves crossed their paths and were transporting some strange, glowing crystals that turned their eyes pure white.
  18. A large painting on the side of the cavern wall depicts a moment of conflict between two mounted knights. In elegant script above the mural it says “Slay the green knight or let pestilence spread.” A pungent odor seems to be coming from the mural.
  19. A trail of littered adventuring goods leads through the tunnel, stopping at a dead end where the body of an adventurer is found lifeless. There appears to be no immediate cause of death, but scratch marks from their hands on the rock make it seem like they were trying to escape from something.
  20. The tunnels that make up the cavern have become noticeably carved and seem to be laid out form a complex grid. It would seem that it would be easier to navigate, but traps continuously being triggered make it hard to keep track of direction.
  21. An old, crazed mage who looks as though he hasn’t seen the sun in years accuses you of being a dragon in disguise and threatens to destroy your eggs that he has hostage if you don’t leave. There does appear to be something egg-like at the back of his cave, but his sanity seems to be gone entirely.
  22. At the end of the passage, the path ends halfway up in a large chamber with a river of lava below. A boat made of giant bones crewed by skeletons is heading down the river and through what appears to be the mouth of a titan’s skull.
  23. Remnants of a tattered dark elf camp show signs of a struggle. Too many items were left behind, a trail of blood leading away in one direction, and tracks made by a serpentine body leading to and from the camp in another.
  24. A curious metal door opens up into a mechanical palace of whirring, spinning, and buzzing contraptions. In the center, different types of creatures, all near death, are hooked up to what appears to be a giant metallic heart.
  25. Crying children huddled in a corner look up hopefully and beg for help. They say their shadows have been stolen and that they need them back in order to leave.

Liked these? Be sure to check out past installments here! And as always, please let us know what type of adventure seeds you’d like to see next!


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