Random Encounters: The Underground World

No, not the familiar roleplaying realm of 10-foot grid squares and angsty Drow. This is the underworld of pulp adventure! In giant caves and artificial tunnels, three factions war for supremacy: the sadistic Deros, masters of ancient super-science; the dreaded Fungus Vampires; and the primordial Cthonians. Explorers may find their way down here through natural caves, or aboard a mechanical mole machine. Getting out is the hard part.

ENCOUNTERS UNDERGROUND

(Roll 1d20 when moving, 1d10 when stationary.)

1. Roll Twice and Combine
2. Plot Advancing Encounter: Someone or something related to the reason the heroes are underground in the first place.
3. Bugs! A swarm of mutant cockroaches capable of generating (and withstanding) high temperatures. Anyone within the swarm takes burning damage, and gear made of cloth or paper may catch fire.
4. Cthonian: A huge silicon-skinned worm with tentacles and a hostile intellect. It cannot speak but can write with acid on the rocks. There is a 50 percent chance it is hungry, and desires only to eat the party, but otherwise it will try to force or bribe humans into serving it.
5. Dero Raiding Party: 2d6 Deros patrolling the caverns in search of runaways, fungal encroachments, or intruders from the Upper World. Half are armed with nerve-whips, the others have flamethrowers.
6. Flood! A sudden surge of water fills the cave you're in. Swim for the exit or risk being swept away.
7. Fungus Vampires: Once members of the Ahnenerbe-SS Hollow Earth expedition of 1940, they are now 1d6 gray brittle monstrosities desperate to feed on living tissue.
8. Giant Salamander: It's big, hungry, and relentless. Though blind, it can sense vibrations and follow a trail by scent, and it can squeeze through any opening.
9. Runaway Slave: A captive of the Deros who decided the chance of freedom was worth the risk. He bears the scars of horrifying surgeries inflicted as punishment, and knows a lot about the hidden empire of the Deros.
10. Tremor! Rocks fall as the earth shakes and shifts. Once the immediate danger is over, you may find old passages blocked and new ones created.
11. Ancient Passages: Artificial tunnels thousands of years old. The carvings on the walls reveal disturbing truths about the origin of humanity.
12. Dero City: A huge cave lit by radium lamps, filled by a labyrinthine city of gold and obsidian. 2d6 thousand Deros live here, with twice that number of slaves. Assume 1/20 of the Deros are trained soldiers armed with flamethrowers or nerve-whips.
13. Egg Chamber: A room holding 3d6 Cthonian eggs. Harming them makes you a giant superintelligent worm enemy for life. But Deros will pay well for them in slaves or ancient super-tech.
14. Fungus Hunters: 2d6 Fungus Vampires pursuing you. The Fungus Intelligence wants something and won't give up until it gets it.
15. Gas Cave: A cave full of methane. You start to feel dizzy after 1d6 minutes, and will pass out and suffocate if you can't get out. And if you have any open flame with you . . . BOOM!
16. Nazi Tunnel Machine: The Ahnenerbe-SS Bohrwagen,long since rusted into immobility. But inside there are usable machine-pistols, drinking water, canned meat, and sealed packets of hardtack. A clever technician can make use of the machine's parts, and it's possible the crew cached some loot here before the Fungus Intelligence took them.
17. Spiders: A cave full of webs and giant albino spiders.
18. Trap! (Roll 1d6) 1-3: Dero Psychic Field prevents you from leaving, 4-5: Fungus Spore Bomb infects you, 6: Crude Snare tangles you for 1d6 rounds.
19. Underground River: A swift and cold river, big enough for boats. Getting across it is a challenge, and one can only sail downstream. Where does it lead? There is a 50 percent chance that swimmers will attract Giant Salamanders or blind cave piranhas.
20. Tracks: Roll again to see what passed recently.

SITUATIONS UNDERGROUND

(Roll 1d6 for a situation, then roll on the table above to determine the parties involved.)

1. A desires B
2. A wants to capture B
3. A wants B dead
4. A wants to go somewhere
5. A wants to solve a mystery
6. A wants X