A Water Trap

The setup for this trap is simple: in the middle of an otherwise unadorned room stands a statue of a monstrous fish rising from a pool of water 10' in diameter and 6' deep. The water is unnaturally clear and pure. At the base of the statue rests a steel lockbox.

The trap functions as follows:

• If a character submerges their head beneath the water (which they would likely need to do to pick up the lockbox), they are subject to a sleep spell

• If the lockbox is removed from the water (say with a net), it becomes impossibly heavy. This should have the effect of dragging the one attempting to lift it into the pool (thus subjecting them to a sleep spell)

• If the lockbox is opened under the water, a catch in the lid tugs a translucent string (imperceivable to the naked eye) which runs to the base of the statue. This causes a small amount of water to drain from the pool and be atomized through the mouth of the statue, subjecting everyone within a 20' radius to a sleep spell (saving throw allowed due to the reduced potency of the atomized water). This also pulls the lockbox back to the base of the statue

The string is detectable if someone runs their hands beneath the lockbox (the string is located in the middle of the box's bottom and would likely not be felt by any standard method of gripping a large lockbox).

The correct method of solving the trap is to bring the lockbox to the surface of the water, disable the catch/unhook the string, and open the lockbox without breaching the water's surface. Alternatively, if one were to tug the catch from a distance and keep it taut, the entire pool could be drained through the statue fairly quickly. Were this to happen, the charm making the box impossibly heavy would be negated and it could be opened normally. The players could also achieve this by scooping the water from the pool.

The room containing this trap should be accessed by a secret door that stays open for several turns so the players have to contend with wandering monsters while they protect their sleeping brethren/attempt to drain the pool.

There are likely further methods to contend with this trap (as well as additional measures to complicate it) but I'll leave that it to individual DMs to embellish.

NOTE: the sleep spell from the enchanted water lasts for 1d4 hours and cannot be ended prematurely by means other than magic