Several bottles of water sit along one wall of this cellar.
|Stairs lead down from above into a cellar, accessed via a large trap door in the floor.
The bottles of water have been magically shrunk to fit. There are other supplies, mostly food, in this cellar. A small hidden trap door conceals a bit of treasure.
A DC 16 Wisdom (Perception) check will show that in the corner, the dust and dirt patterns on the floor are different. If this is investigated, a small trap door is found.
The trap door requires a DC 14 Dexterity check to unlock, or can be broken with a DC 16 Strength check, or by destroying it. It is AC 16 with 10 hp.
A spell or other effect that can sense the presence of magic, such as Detect Magic, reveals an aura of abjuration about the trap door and the cellar door, and an aura of transmutation around the water bottles.
A small hole under the door contains 3 bags of coins. However, if the door is opened without disabling the trap, it creates an antimagic field in the room for 1 hour.
This antimagic field causes the bottle to grow and break, flooding the room. Those in the room must make a DC 14 Dexterity save or become stunned for 1 round. Since the room is filled with water, every creature in the room is subject to drowning. The water fills the room to the ceiling.
The door to the cellar is kept open via magic. When the magic is disabled via the antimagic field, it locks. Opening it requires a DC 14 Dexterity check that has disadvantage if thieves’ tools are not used. It can also be broken with a DC 16 Strength check or by attacking it. It has AC 16 with 20 hp. Creatures underwater that attack or attempt to break the door do so at disadvantage.