You find a damp stone chamber where green light shimmers across a wall of water. A waist-high gate blocks the far passage, its seams trembling as water presses through. Three tarnished bronze controls stand beside it: a wheel, a lever, and a crank, each stamped with a simple mark. The wheel hums with the rush of the inlet; the lever's channel is dry and furred with moss; the crank shivers under the gate's strain. An inscription is cut above them.
You step into a wet stone chamber. A wall of water presses against a heavy gate, and three bronze controls tremble beside it. Rushing water, a dry side channel, and a strained crank each seem tied to a different part of the mechanism. An inscription waits above the controls.
The inscription is legible. Characters can inspect the controls, listen to the water, or test a control. A wrong step gives a clear warning: the mechanism groans, the blue marks flare, and the controls return to their starting positions.
Let the inscription and physical layout do most of the work. If players debate without progress, offer the tier 1 hint after a minute, then tier 2. Use tier 3 if they are stuck. Keep mistakes noisy and wet, not deadly.
You find a damp stone chamber where green light shimmers across a wall of water. A waist-high gate blocks the far passage, its seams trembling as water presses through. Three tarnished bronze controls stand beside it: a wheel, a lever, and a crank, each stamped with a simple mark. The wheel hums with the rush of the inlet; the lever's channel is dry and furred with moss; the crank shivers under the gate's strain. An inscription is cut above them.
The controls and inscription are visible as soon as the characters approach the gate. Scraping moss from the lever's channel reveals that it curves around the barrier and rejoins the downstream passage.
When the river bears its weight,
Give the side path first its share.
Then still the mouth that feeds the flood.
At last, raise stone from water's hold.
The characters can operate the controls by hand without checks. The inscription gives the order: open the bypass lever, close the inlet wheel, then turn the gate crank. After each correct step, the mechanism gives reassuring feedback: the bypass begins to gurgle, the pressure against the gate slackens, and the crank stops shivering. Turning the crank before shutting off the inlet triggers a forceful splash and resets the controls. Other approaches that reduce pressure or safely provide leverage can work too; judge them by whether they address the same physical problem.
The puzzle begins when a character touches any of the three controls or examines the inscription closely.
| DC | Check | What it gives |
|---|---|---|
| 10 | Investigation | Notice that the bypass channel runs around the gate and that its open position will reduce pressure. |
| 10 | Arcana | Recognize that the faint blue glow marks a pressure-sensing enchantment, not a dangerous attack. |
| 10 | Perception | Hear the differences between the rushing inlet, the quiet bypass, and the gate's strained groan. |
No hint given yet.
The gate rises smoothly, water drains through the bypass, and the downstream passage becomes accessible.
The pressure jolts the mechanism, splashing everyone in the chamber and resetting the controls. Each character in reach of the spray must succeed on a DC 10 Dexterity saving throw or be knocked prone. The water does not deal damage, and the party can try again.
The floodwardens of the old river town built this gate to protect the settlement below from sudden surges. Its three controls were deliberately arranged so a keeper had to relieve the water pressure before lifting the heavy gate. After the town was abandoned, moss and mineral deposits obscured the markings, but the instructions remain intact.
For a larger or more capable party, add a second gate crank that must be turned at the same time, allowing teamwork without making the puzzle more obscure. For a very new group, the inscription can explicitly say, 'Open the side path, still the inlet, then raise the gate.'
Do not require checks to read the inscription or operate the controls. Checks provide confirmation or useful observations, not the answer itself. Accept sensible descriptions of leverage, spells, or improvised tools as alternate solutions. The harmless spray signals that the mechanism has reset.
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