With thanks to friend of the blog Sofinho over at Alone in the Labyrinth for the prompt:
1. Big red button labelled "self-destruct". If you press it you become an alcoholic.
2. Pressure plate that makes the walls appear to close in on you when you step on it. In fact, stepping on it releases a psychedelic gas that induces Alice in Wonderland Syndrome.
3. Massive guillotine-blade hangs across the ceiling. Ropes leading up to it can be drawn to drop the blade or pull it back up. Heads severed by the blade transform into vargouilles, other severed parts become different sorts of undead monsters (e.g. hand to crawling hand, leg to hopping stomper, etc.).
4. Lever labelled "do not pull". If you pull the lever it will open a trapdoor beneath you that leads to a pit filled with water and hungry piranhas. If you instead push the lever it opens a secret door.
5. One wall of room is covered in holes. Along the ground is a tripwire which when triggered will cause the holes to become powerful vacuums, drawing any loose objects towards them. Getting caught on a hole deals 1d6 damage per round as your shit gets slurped (like that video of a crab getting sucked into a pipe). Due to the pressure the doors require a combined strength of 18 to open while the holes are sucking air in.
6. Deep pit that passes through multiple dungeon levels, like an elevator shaft without the elevator. If you tap the right code onto the wall of the shaft you'll be able to walk along the wall as though it were horizontal. A family of ghouls that knows the code lurks near the bottom of it and will attack those who attempt to rappel down.
7. Bottle bearing embossed skull and crossbones. If you drink it, save or your skull will steal some of your bones and escape your body as an cat-sized creature. Swallowing the creature (possible to do whole thanks to your boneless jaw) will return your bones.
8. When you enter the room a large clock with various wires and pipes running through it begins ticking. After ten minutes the clock will count down to zero. If you are still in the room when that happens it will reset to ten minutes and your temporal duplicates will enter the room through the same entrance you used. If you both leave the room then the last one to leave will disintegrate. You know this instinctively, but your duplicate does not.
9. Demon trapped inside a pentagram of salt, will promise lavish favours if freed. Demon is in fact a psychic space slug telepathically translating itself to the closest thing your mental context can comprehend. Lavish favours are true, but translated from things a psychic space slug would want, such as immense quantities of crisp, fresh cabbage.
10. Floor is lined with rakes. If you step on them they will break and the mushroom farmers a few rooms over will be upset with you.
11. Ceiling is covered in spikes impaling rotten corpses. Door out of room is opened by one of two buttons. Pressing the wrong button causes the spikes to retract and release the corpses, which wake up when they hit the ground. They are zombies.
12. One of the walls in the room is an aquarium with cracked glass. Within the aquarium are irate sharks. Sitting on a stool beside the glass is a fat opera lady who wants to show off her singing, which although impressive is at the resonant frequency of the aquarium's glass.
What's the twist? (1d4):
- If you bully her she will stop singing and start crying but her crying is also at the resonant frequency of the glass.
- The fat lady is actually a disguised siren and the sharks are her pets.
- The glass is actually a television screen. Behind it are men in white lab coats taking notes.
- When people say "it ain't over till the fat lady sings" this is the specific fat lady they are referring to.