Random Table: 1d10 Underground Hazards

Oct 04, 2025

The subterranean world is perilous. Not only is the stalwart adventurer like to encounter deadly traps and ferocious monsters, but also natural forces with which he must contend if he hopes to return to the surface alive—or at all.

When a party is delving in caves and caverns beneath the earth, the game master should periodically make an underground hazards check; on a roll of 2 or lower, a hazard occurs. Roll 1d10 and use the following table to determine what.

1. Tremors & Quakes – sudden earthquakes trigger rockfalls, destabilize footing, or cause cave-ins of nearby passageways.

2. Poisonous Gases – pockets of CO2, methane, or sulfur displace breathable air, causing dizziness, blackening vision, unconsciousness and, if careless, death.

3. Magma Pockets – superheated vents threatening to erupt (1-in-2 chance, inflicts 1d10 damage on any entity within 10 feet) or glowing seams of molten rock radiating intense heat.

4. Unstable Floors – sinkholes, thin crusts, or mudstone that will collapse under weight and into hidden depths 1d10 x 5ft below (Reflex Save).

5. Crystal Growths – large, jagged crystals that dazzle the eye, and may cut careless cavers or block passages.

6. Acidic Pools – sulfuric or otherwise corrosive water that will eat away at flesh (inflicting 2 damage per round) and metal (completely destroying equipment in 1-3 rounds).

7. Flooding Chambers – sudden surges of water from an underground river or spring that can rapidly fill tunnels or rooms.

8. Veins of Fire-glass – these fragile seams contain dancing flames, and if broken open, a small explosion occurs (inflicting 1d5 damage on any entity within 10 feet).

9. Whispering Stones – glittering rock walls that echo back sounds and voices, though they contain strange sounds and unuttered words.

10. Stalactite Collapse – fragile formations that break loose in a chain reaction, falling like spears and inflicting 1d10 damage (if struck, Reflex Save to reduce by half).

Note: This table was inspired by my friend Crimson Jester; I strongly recommend you follow him for interesting tabletop RPG content and discussions!