On The Thursday Trick, Acid Pool

Acid Pool (Special)

Trigger: Other: Player Greed Effects: Liquid
Never Miss
Alchemical Device
Save: None Duration: Instant
Resets: Automatic Bypass: None (Avoid)

Description: This trick is designed to punish player greed and thoughtlessness. This trick is best placed off in a small side-room somewhere off the beaten path. There should be a basin of some sort, whether it is natural or worked is unimportant - what is important is that the basin is of some silicate.Something like quartz, fieldspar, or clay will do. The basin should be at least 3' deep, but not more than 5'. It is also important that the ceiling is jagged, poorly lit, and has many small crevices.

Inside the basin is what appears to be a magical pool. The air over the clear liquid seems to shimmer in front of your eyes. Anyone reaching approximately 8' of the pool will be able to see what looks like a large cut gemstone in the bottom.

The gemstone is a reflection of a piece of cut quartz lodged in the ceiling. The pool is filled with sulfuric acid. Anyone reaching in the pool will take 8d6 damage or 25% of their hit points, whichever is less. If they take the 25% of their hit points, their limb is useless - it is the DM's prerogative as to whether or not it can be healed.

Detection/Disarming:  There are several ways this trap could be detected. Nice GM's could put skeletons missing arms nearby, but even without obvious clues, anyone moving close enough to stand over the pool will feel a burning pain in their eyes and lungs as they take 1d3 damage from the acid vapor. Careful examination of the jewel may clue the players into something being not right with the jewel. Using a torch to examine the ceiling closely will display the rock quartz clearly. The ceiling being located over an acid pool would naturally end up being somewhat irregular, which is another clue.

And of course a basin made from clay or quartz containing liquid should be a large clue to the intelligent player.

My first exposure to this trap came from the Choose Your Own Adventure book, the Dungeons of Dread. The trap was a water weird and not acid, but the effect is the same.


  1. It's also treasure: bottle that acid in a glass flask for a super deadly molotov cocktail, or sell it to an alchemist. Nice.

  2. To combat this, you could make it Hydrofluoric acid, which reacts violently with glass. Also, it doesn't so much burn like acid, but in addition to causing the damage, force the players to make a system shock roll in order to survive the heart attack that will happen 4 hours later.

    Also, the pool will have to be made from lead.

  3. Can't you just see some rich noble using his quartz basin to set a trap for his thieving maid?


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