The circular stone chamber smells of wet limestone and old iron. Blue light wavers across a shallow basin, a bronze bell, and a barred gate set into the far wall. Three handles stand on a waist-high plate, each stamped with a channel, a bell, or a rising gate. Water ticks through a narrow sluice, and every few seconds the gate gives a low, expectant groan.
You step into a round chamber where water whispers through the stone. A blue-lit basin sits beneath a bronze bell, and a barred gate blocks the far passage. Three heavy handles wait beside the basin. The gate shivers once, as if something below it is still awake.
The handles are marked with a channel, a bell, and a rising gate. A short inscription is cut into the control plate. Pulling any handle is possible, and the machine answers with a visible change, so players can learn from experimentation.
Give the players time to read the inscription and test the basin. Offer a tier 1 hint after a few minutes of circular discussion, tier 2 if they still lack a plan, and tier 3 when they are ready for the near-solution. Do not impose a real-time countdown.
The circular stone chamber smells of wet limestone and old iron. Blue light wavers across a shallow basin, a bronze bell, and a barred gate set into the far wall. Three handles stand on a waist-high plate, each stamped with a channel, a bell, or a rising gate. Water ticks through a narrow sluice, and every few seconds the gate gives a low, expectant groan.
The controls and basin are immediately visible. The etched instructions are legible without a check; checks can clarify the mechanism and its feedback, but are not required to solve it.
Etched above the handles:
Let the channel feed the hollow stone. When the water meets the measured line, wake the bell and hear its full voice. Only after the bell has spoken may the barred road rise.
The three handles are marked:
Players may pull any of the three handles, and the mechanism gives immediate, visible feedback: the channel handle admits water, the bell handle tests the basin's pressure, and the gate handle releases the counterweight. The etched instructions state the necessary order and conditions. The intended sequence is to open the channel, wait until the basin fills and the bell rings clearly, then raise the gate. Pulling the bell handle too soon produces only a hollow click; pulling the gate before the bell sounds triggers the harmless failure effect. No check is required to read the instructions or operate the controls.
The puzzle begins when a creature touches or pulls one of the three handles.
| DC | Check | What it gives |
|---|---|---|
| 12 | Intelligence (Investigation) | Notice the narrow water channel from the sluice to the basin and the drain beneath the gate. |
| 13 | Intelligence (Arcana) | Recognize that the bell's faint vibration is part of a pressure-lock mechanism, not a magical ward. |
| 12 | Wisdom (Perception) | Hear that the bell rings with a full, sustained note only when the basin is full. |
No hint given yet.
The bell rings with a clear bronze note, the counterweight lifts, and the barred gate rises smoothly into the ceiling. The passage beyond is dry and safe to enter.
The counterweight releases a brief spray of cold water. Each creature adjacent to the control plate must succeed on a DC 12 Dexterity saving throw or be knocked prone. The handles reset after one minute, and the puzzle can be attempted again.
The dwarven engineer Hesta Vell built this gate to test apprentices entrusted with the old aqueduct. Its controls taught a simple but essential lesson: water must be admitted before its level can be measured, the warning bell must sound before the counterweight is released, and the gate should move only after the mechanism is ready. When the aqueduct was abandoned, the test remained in place, still waiting for careful hands.
For a lower-pressure version, make the basin fill quickly and have the bell handle visibly tremble when it is ready. For a more challenging version, have the basin's drain partially clogged so the party must find and clear it with a DC 13 Strength (Athletics) check or appropriate tools before the water can reach the line.
Treat the inscription as a fair, complete clue rather than requiring a check to understand it. Let players try reasonable ideas, and describe the apparatus's feedback clearly. A failed attempt should teach them which condition was missing, not conceal information or block progress.
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