The Observatory at Low Tide
The Observatory at Low Tide
Read aloud
The harbor tide bells ring at midnight, though the sea is pulling away from shore. Harbor tidekeeper Mara Venn offers a reward to anyone who can enter the newly exposed observatory of Veyra, recover its tide ledger, and find out why the water is retreating.
Run the session
Cheat sheet
Objectives
- 11. Reach the observatory.
- 22. Recover the tide ledger.
- 33. Resolve the tide engine's threat.
- 44. Optional: uncover what happened to the missing tidekeeper.Optional
The clock
The sea returns after roughly four major actions or setbacks following the party's departure from shore. Each delay, noisy fight, failed hazard attempt, or extended negotiation advances the clock. At the first turn, the causeway begins flooding; at the second, the entrance becomes dangerous; at the third, escaping by the causeway requires a risky alternative route or rescue.
Scenes
- 0:00The Bell at Midnight
- 0:25The Exposed Causeway
- 1:05The Instruments Stir
- 2:05A Channel for One
Cast
- Mara VennQuestgiver and harbor tidekeeper
- Tallis ReedAlly and apprentice chartmaker
- Captain Orvek SornAntagonist and privateer
- Pell DaroWitness and former deckhand
The hook
Set the scene
Read aloud: The tide bells ring once, twice, then a third time from somewhere beyond the harbor. The sea draws back from the beach, exposing a black spine of rock and the upper stones of an ancient observatory. Mara Venn presses a brass chart tube into your hands. "Bring back the ledger before the tide returns. And if you hear someone calling from below, do not answer until you know who it is."
How Mara Venn asks
Mara Venn approaches the party at the harbor tidehouse shortly after a strange midnight ebb.
She offers a written payment agreement, a rough route to the observatory, and a warning that the exposed causeway will be passable only until the tide turns.
Rumours
Scenes
about 3.5 hours0:00
25 min
socialThe table is here
1. The Bell at Midnight
The harbor tidehouse, with a view of boats resting in mud as the sea withdraws.
Mara explains the mission and offers the reward. Pell Daro can describe Sorn's crew entering the ruins and warns that the tide is already turning.
NextMara gives the party a route across the exposed shore. A fresh line of foam shows how little time they have before the water returns.
0:25
40 min
exploration
2. The Exposed Causeway
A newly exposed reef and the broken outer wall of the observatory.
The party crosses unstable rocks and reaches the observatory entrance. They can choose a direct slippery causeway or a longer climb to a dry service entrance. Signs of Sorn's passage point toward the upper galleries.
NextThe party enters a gallery where seawater moves through cracks in the stone and old bells shiver without wind.
1:05
60 min
combat
3. The Instruments Stir
A flooded instrument gallery beneath the observatory's ruined dome.
The party navigates rising water, broken instruments, and hostile scavengers or a brinebound sentinel. Clues in the gallery show the engine has been activated recently.
The Flooded GalleryNextThe party finds the chart room and the tide ledger, but a recently lit lantern and fresh footprints lead toward the lower chamber.
2:05
75 min
social
4. A Channel for One
A circular chamber where brass arms turn above a flooded central pit and the lens casts moving reflections across the walls.
The party confronts Sorn at the tide engine. They can fight, negotiate, deceive him, or manipulate the controls while he is distracted. They learn enough to choose whether to stabilize, disable, or destroy the engine.
The Tide Engine ChamberNextOnce the engine is resolved, the tide changes. The party must return to the harbor with the ledger, Sorn's fate, and evidence of their decision.
Behind it
What people believe
Mara Venn, the harbor tidekeeper, asks the party to explore the newly exposed observatory of Veyra, recover its tide ledger, and investigate an unnatural retreat of the sea.
Captain Orvek Sorn and his crew have also entered the ruins, hoping to claim the observatory's controls. The party must navigate rising water and a failing mechanism, then decide what to do with the device before the next tide threatens the harbor.
Background
The drowned observatory of Veyra once charted the seasonal tides and guided ships through the Needle Strait.
Three nights ago, a landslide exposed its upper galleries. Since then, the harbor's tide bells have rung at impossible hours, and the water has begun retreating from the coast even when the moon says it should rise. The observatory's brass instruments were built to measure the tides, but its sealed lower chamber was designed to alter them.
The stakes
If the engine remains uncontrolled, each unnatural ebb strands vessels, threatens lives, and may permanently alter the harbor's channels.
If the party destroys the lens without understanding it, a dangerous surge may hit the coast. If Sorn gains control, he can decide which ships pass safely and which are left to the tide.
Encounters
2The Flooded Gallery
Combat
A narrow stone gallery with knee-deep seawater, broken instrument stands, waist-high plinths, and two dry ledges. The water deepens during the encounter.
Foes
2 reef scavengers (use an appropriate low-threat beast or humanoid stat block)
1 brinebound sentinel (custom construct; use a suitable low-threat construct stat block)
ComplicationAt the end of each round, or after a significant delay, water rises across one low section of the gallery. A creature in rising water must get to higher ground or risk being knocked prone and having small loose objects swept away. This is a custom environmental hazard, not a standard monster ability.
ScalingFor level 3 or a small party, remove the sentinel. For level 5 or a large party, add one reef scavenger. Keep the rising-water hazard telegraphed and provide climbable ledges.
The Tide Engine Chamber
Combat or social
A circular chamber around a waist-high central engine, with stairs, narrow walkways, a flooded pit, and the great lens overhead. Characters can use the control levers to halt the sweeping arm or alter its path.
Foes
Captain Orvek Sorn (use a suitable veteran or bandit leader stat block, adjusted for the party)
2 Sorn deckhands (use suitable low-threat humanoid stat blocks)
ComplicationThe tide engine is charging. At the end of each round, a rotating brass arm sweeps across one marked lane. Anyone in that lane can move clear with a suitable check or take modest bludgeoning damage. The arm's path is visible before it moves.
ScalingFor level 3, Sorn tries to bargain and flees if reduced to about half his hit points; use one deckhand. For level 5, use both deckhands and give Sorn one additional defensive option appropriate to the chosen stat block. Avoid adding a second high-threat enemy.
Cast
4Mara Venn
QuestgiverQuestgiver and harbor tidekeeper
WantsRecover the ledger to prove the harbor's strange tides are not a natural disaster and protect the town's fishing fleet.
“Bring me the observatory's tide ledger, and I will pay for the danger. Do not touch the great lens.”
Tallis Reed
Ally and apprentice chartmaker
WantsFind her missing mentor and prevent the observatory's mechanism from being used to control the coast.
“The old charts are not wrong. Someone has been teaching the sea a new rhythm.”
Captain Orvek Sorn
Antagonist and privateer
WantsUse the observatory's tide engine to create a permanent safe passage for his ships, whatever the cost to nearby settlements.
“I only want one safe channel. The sea takes what it wants, so why should I not bargain with it?”
Pell Daro
Witness and former deckhand
WantsWarn others about the observatory and make amends for helping Sorn's crew enter its grounds.
“The bells rang before the water moved. I heard a voice inside the lens, and it knew my name.”
How it ends
Rewards
Items
A tideglass compass, a custom uncommon utility item that points toward the nearest coastline while within sight of the sea
A water-resistant chart case containing regional shipping routes
One salvaged brass instrument worth 25 gp to a collector
On a win
The party recovers the tide ledger and prevents the engine from causing another uncontrolled ebb.
If they stabilize or safely disable it, the harbor's tides return to a predictable pattern. The fate of Jalen and the bound memories depends on the party's choices, and Sorn may remain a threat if he survives or escapes.
What it leaves open
If it fails
- The observatory's lens discharges and draws the harbor water sharply outward. Several boats are stranded or wrecked, and the characters must rescue anyone left in the exposed channel before pursuing the ledger.
- The characters do not retrieve the tide ledger before the engine destabilizes.
- The coast experiences another unnatural ebb. The immediate threat ends only after a dangerous evacuation, and the harbor loses access to its usual fishing grounds until the engine is repaired or destroyed.
- The characters leave the tide engine running or damage it without understanding its controls.
- Sorn gains leverage over the harbor and can return with allies, creating a future adventure involving his attempt to monopolize the safe channel.
- Sorn escapes with the ledger or a usable fragment of the engine's controls.
Complications (d6)
- 1A sudden ebb exposes a slick, barnacle-covered route, but the water will return in ten minutes. Crossing requires careful movement or a sensible alternative.
- 2A tide bell rings from beneath the observatory. Each character hears a different person's voice calling them toward the lower stairs.
- 3A gallery floor gives way, separating the group. The separated characters can see one another through the broken floor but must find a safe route back together.
- 4Sorn's lookout spots the party and signals the crew. The next hostile group is alert and has time to take cover.
- 5The great lens turns by itself and focuses a beam on one carried metal object, heating it until dropped or moved out of the light.
- 6A pocket of brackish water bursts from a wall. It sweeps loose gear toward a drain and leaves the floor difficult to cross until the water recedes.
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