The corridor ends at a circular steel door set into black stone, its center formed from overlapping iris plates. A waist-high plinth hums softly beside it, with three brass-edged dials beneath milky glass. Cyan light pulses through the seams in a slow, uneven rhythm, and the air smells faintly of hot dust and rain. Scratched arrows on the dials point toward tiny etched symbols, while the door's iris twitches whenever a selector clicks into place.
You enter a short chamber of black stone and metal. A circular door blocks the far wall, its overlapping plates shivering with a faint cyan glow. Beside it, three brass-edged dials click softly as the light pulses through the plinth. A scratched plate bears a sequence of symbols and a few lines of blocky script.
The dials turn freely and settle into distinct notches. The instruction plate is readable, and its symbols appear on the selectors. The iris reacts to each click, but no single setting opens it. Let players inspect, translate, test, or improvise; checks clarify the machinery without replacing the clues.
Give the group a few minutes to compare the plate with the selectors. If they overlook the sequence, use a DC 13 Perception check to point out the worn settings. If they are stuck, offer the tier 1 hint, then escalate only when discussion stalls. Failed attempts cause a brief, harmless reset.
The corridor ends at a circular steel door set into black stone, its center formed from overlapping iris plates. A waist-high plinth hums softly beside it, with three brass-edged dials beneath milky glass. Cyan light pulses through the seams in a slow, uneven rhythm, and the air smells faintly of hot dust and rain. Scratched arrows on the dials point toward tiny etched symbols, while the door's iris twitches whenever a selector clicks into place.
The selectors are clearly intended to be operated by hand, and the instruction plate gives a short startup procedure. The symbols on the controls match those on a small diagram etched into the plate.
STARTUP SEQUENCE
CONTROL TRANSCRIPT
The players may turn each selector freely and attempt to activate the plinth; no check is required to operate it. The controls must be set in the order shown by the plate: source, circuit path, then access sensor. A correct setting makes one indicator glow steadily, while a wrong one flickers and dims; activating an incorrect complete combination triggers the harmless reset described under failure. A DC 15 Crafting check or suitable Recall Knowledge check can clarify the machinery, while DC 13 Perception reveals the worn preferred positions. These checks provide guidance but are never required to read the plate or solve the lock.
The puzzle begins when a character turns any selector or presses the activation stud.
| DC | Check | What it gives |
|---|---|---|
| 13 | Perception | Notice that each dial has a worn preferred position and that the small arrows point toward the same symbols shown on the instruction plate. |
| 15 | Crafting | Understand that the controls describe a startup sequence: power source, circuit path, then access sensor. This gives the procedure, not the exact settings. |
| 15 | Society or relevant Lore | Recall that old orbital equipment often used a sun symbol for a steady power input and a closed-loop symbol for circulating current. |
No hint given yet.
The indicators brighten in sequence, the plinth emits a clear three-note chime, and the iris plates retract into the wall. The passage beyond opens without a dangerous discharge.
The plinth discharges a harmless static snap and releases a puff of warm, dusty air. The dials return to their starting positions, and the party loses 1 minute. After three failed activations, a reserve cell runs low: the indicators dim, but the lock remains operable.
The station engineer Vey Ansel built this lock to keep an unstable transit core from activating during a power failure. Its three controls encode the safe startup procedure: provide a steady dawn-like power source, circulate the energy through a closed circuit, then wake the iris that guards the passage. After the station was abandoned, the lock remained powered by a weak reserve cell and continued to test anyone seeking the sealed vault.
For a lower-pressure session, have each correctly set dial remain locked in place after a failed activation. For a more challenging version, make the selectors spring back after one minute unless held, without increasing the check DCs or adding damage.
Treat checks as assistance, not a gate: the complete clue is visible to the players. Let experimentation reveal feedback without imposing damage. Reward reasonable uses of light, electricity, tools, or physical circuit tracing if they satisfy the device's stated sequence. The lock is an obstacle, not a combat encounter.
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