Water-Filled Dungeon Trap
This variant is best used on the bottom floor of a multi-level dungeon. This room’s doors aren’t waterproof and don’t lock: ignore all text about locks. When the water level rises, it rises for the entire dungeon instead of merely inside the room, starting at the bottom of the dungeon and rising until the entire dungeon is submerged. When placing this trap, make sure that escape is possible for adventurers—and decide what happens to dungeon denizens that can’t breathe water!
If the door to the room closes, it automatically locks. When it does so, water begins gushing from the gargoyles’ mouths. Roll initiative. On initiative count 20 and 10, the water level in the room rises 1 foot. Once the water is higher than a creature’s height, that creature must swim. After 3 minutes, the room completely fills with water and begins to drain at a rate of 2 feet per round. When the room is completely drained, the door unlocks.
Door. An Engineering or Investigation check, or an examination of the door, reveals that it is fortified with two metal bands, each of which has a separate lock. Experimentation reveals that the locks allow free entry into the room but not out. The door gently closes by itself if not held open. The door has AC 15, 27 hit points, immunity to poison and psychic damage, and a damage threshold of 15.
Depending on the dungeon’s floor plan, there may be other doors in the room, each of which is similarly locked and fortified.
Gargoyles. An Investigation or Perception check, or an examination of the gargoyles, reveals that the gargoyles’ tongues are coated with algae. Their throats are spouts that lead into the walls.
Spell Solve. Knock unlocks one of the door’s two locks. Water breathing and similar spells allow creatures to survive the flooded room.
- A creature can make a thieves’ tools check to unlock one of the door’s two locks. This check is made with disadvantage if the lock is underwater. The lower lock is two feet high and the upper lock is four feet high.
- A creature can make a Strength check to plug a gargoyle’s spout with an object.
- A creature that casts a spell that deals cold damage can make a spellcasting ability check to plug a gargoyle’s spout with ice.
Potential Outcomes
Critical Failure. A critical failure to pick a lock permanently raises the lock’s DC by one. A critical failure to jam a gargoyle’s spout causes the spout to crack, raising the DC for that spout by one.
Failure. The attempt fails.
Success. One of the door’s locks is picked, or one of the water spouts is jammed until the start of the triggering creature’s next turn. When both of the door’s locks are unlocked, the door can be opened, pouring water into the nearby rooms and disabling the trap. While one vent is plugged, the water level doesn’t rise on initiative count 10. While all four are plugged, the water doesn’t rise on initiative count 20 or 10.
Critical Success. The creature picks both the door’s locks or permanently jams one of the water spouts.