Eleusis, Caverns of Danger, 09. Alarm System
The ceiling is 30 feet high at the northwest end of the cave and gradually slopes down to 20 feet high as the cavern narrows into a passage that leads to the south.
Passageways lead to the northwest, south and east.
Hazards & Traps
The uneven rock floor is dotted with small stalagmites, between which run nearly invisible trip wires made of webbing. These web strands set off hidden rockfall traps. Thin web strands between some of the stalagmites, creating trip wires. Any creature that enters a square marked T on the map has a 50 percent chance of breaking a strand and triggering a trap that releases rocks from a hidden crevice in the ceiling. If a trap triggers, all creatures occupying the trapped square must succeed on a DC 14 Dexterity saving throw or be struck by a falling rock for 5 (1d10) bludgeoning damage. In addition, the sound of the falling rocks alerts the driders in area 10. A character adjacent to a trapped square or in a trapped square can spot the trip wires with a successful DC 17 Wisdom (Perception) check, then track the thin webs to the point in the ceiling where the rocks are hidden. Once it is spotted, a rockfall trap can be disabled with a successful DC 12 Dexterity check by a creature in the trapped square; failing this check triggers the trap.