12 Natural Cavern Hazards

Caverns can be dangerous places. As well as the ever-present threat of ambush from the various fell denizens dwelling within, the very caverns themselves can be dangerous to unwary travellers and explorers.


Use the features below, to add obstructions and realism to the PCs’ explorations. Additionally, these features can be incorporated into encounter areas to add an extra level of excitement and challenge (and to add options for clever, tactical play).

  1. Rubble: Rubble and mud obscure the floor, making it uneven and slippery and slowing movement. In places, the rubble is precariously balanced and characters moving through the area without due caution could slip and fall.
  2. Crumbing Escarpment: A crumbling escarpment cuts across the passageway, making further progress without climbing impossible. Loose rocks and small boulders cover the escarpment’s face.
  3. Crumbling Sinkhole: A water-filled sinkhole pierces the ground. The floor immediately adjacent is crumbling and unsafe (which a wary or perceptive character will notice).  Characters entering an unsafe square may cause it to collapse. If it does, the character is dumped into the frigid and turgid 20-foot deep water.
  4. Fissure: A fissure cuts across the floor. Between 5- and 20-foot wide, a faint, cold breeze emanates from its depths. The fissure’s rugged walls plunge 50 ft. and terminate amid a field of jumbled rubble.
  5. Thick Mud: Thick mud coats the floor. In most places the mud is little more than a few inches deep. In other places, however, it hides holes into which an unwary explorer could stumble. The holes range from a half-foot to two-foot deep.
  6. Long Stalactites: Glistening stalactites hang down from the ceiling. In places they are barely five-foot above the ground, forcing most humans to duck. Water drips down the stalactites, making the floor beneath slick.
  7. Geyser: Mud covers the ground adjacent to a narrow hole piercing the floor. Every ten rounds, the geyser explodes coating everything within 20 ft. with thick, hot mud. The round before it explodes, perceptive characters hear a deep rumbling from far underground.
  8. Stalagmites: Thick stands of stalagmites cluster about the area, creating areas of natural cover and concealment.
  9. Precarious Boulder: A precariously placed boulder atop a steep slope looks like it could tumble downwards at any moment. Only a few smaller stones wedged under it keep it in place. Characters removing these stones cause the boulder to roll down the slope, crushing anything in its path.
  10. Subterranean Stream: A subterranean stream cuts through the area. Its water are cold and swift, and its bank steep. In most places, the stream is only about 10 ft. wide, but in one spot it widens into an irregularly-shaped pool before continuing on its way.
  11. Unstable Ceiling: Great cracks run through the ceiling. These cracks and the resultant rubble covering the floor are obvious to even the most unperceptive explorer. Loud noises, explosive spells or any kind of mining cause the entire ceiling to collapse, burying anyone caught underneath.
  12. Powerful Wind: Powerful winds periodically rush through this narrow cavern. The winds are so strong they extinguish all unprotected flames and have a 50% chance of extinguishing protected flames such as lanterns. Three rounds before the wind fills the chamber, perceptive PCs hear a moaning sound coming rapidly closer. Everyone hears the wind approaching on the round.

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20 Things II_SNE_220This article will appear in GM’s Miscellany: 20 Things II, available in March 2017.

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