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Dungeons
Sewer · Large · Level 6 · Hard

Vasker's Drain

The first thing you notice is the water climbing the stone in a fresh, dark line.
Rooms
23
Foes
28, CR 1/4 to 7
Traps
7
Treasure
1,912 gp
1234567891011121314151617181920212223Entrance
Select a room on the plan to open it.

The party is in

1. Street Sluice

Seen

Something wanders by

At a glance

The threat

At the bottom of the complex, the cult's leader has become a drowned oracle, sustained by the sealed spring and the bodies cast into it.

Wandering monsters (1d3)

  1. 1

    2× Sewer giant ratsCR 2

    When: A loud fight, spilled food, or a character lingering beside a drain for more than a minute.A pair of broad-backed rats, slick with sewer slime, follows food smells and attacks anything that blocks its route.
  2. 2

    Drain crawlerCR 3

    When: A creature bleeds in a corridor or a flood surge shakes loose debris.A pale, eyeless carrion crawler travels through the channels with its feelers tasting the air.
  3. 3

    1d4× Sluice runnersCR 1

    When: An alarm sounds in rooms 1, 2, or 13, or the party leaves a door unsecured.Cult runners in soaked gray wraps hurry between posts carrying bells, keys, and scraps of ritual orders.

Rooms

23
1

Street Sluice

treasuresecret

What they see

Read aloud

A stone landing stands above a black drainage channel, with a ladder rising to the street and four exits leading deeper into the works. Muddy bootprints cross older mason's marks, and faint voices carry from the barracks beyond.

Features

  • The street ladder can be climbed quietly with a Dexterity (Stealth) check.
  • The southern locked door opens with a Dexterity check using thieves' tools or a key from room 1.
  • A secret door in the west wall is hidden behind a hinged inspection panel.

What the GM knows

Treasure

Lost maintenance purse18 gp and a brass key to room 4

A watertight oilskin pouch caught in the ladder rungs.
Room secrets · GM only

Notes

The entrance should signal both a working sewer and a recent human presence. Noise here can alert room 1 or room 2.

1 door: W (locked)

The place

What it is

Vasker's Drain is a sprawling municipal sewer built over older stonework and later claimed by a hidden cult.

Atmosphere

Cold runoff carries a smell of wet stone, lamp oil, and old blood.

The threat

At the bottom of the complex, the cult's leader has become a drowned oracle, sustained by the sealed spring and the bodies cast into it.

History

The first channels were laid by city masons beneath a riverside district, then expanded by a forgotten engineer called Vasker, whose name survives only in the drain's oldest inscription.

Rumors

1d4
Roll a rumor

  1. 1The old drains have started running warm at night, and the water tastes faintly of copper.
  2. 2A maintenance crew heard bells ringing below the streets, though no one was assigned to the lower works.
  3. 3People who disappear near the riverside are sometimes found weeks later with clean clothes and water in their lungs.
  4. 4The city watch sealed an entrance to the sewer after something dragged a guard through the bars.

Plot hooks

3
InvestigationThe Bitter TapThe city water has turned brackish, and a worker vanished while checking a blocked culvert. The party must reach the old controls and learn what is poisoning the flow.From: Terek, a blunt-faced municipal inspectorReward: A purse of 250 gp and a city-issued charm that grants advantage on one check to resist disease
RescueA Name in the GrateA prisoner's family has found a coded plea scratched into a confiscated belt buckle. The captive is alive in the cells, but the cult plans to use them in its next flood rite.From: Zsena, a candle seller whose sibling disappearedReward: A silvered weapon and the family's hidden cache of 150 gp
Urgent perilClose the Lower GateA floodgate has jammed open beneath the district, and water is already rising in the low streets. The mechanism is accessible through the barracks, but the cult has made the control room a proving ground.From: Kovik, a watch sergeant with a map of the old channelsReward: A 300 gp civic bounty and permission to keep any recovered relics

Corridors

4

  • Between rooms 0 and 3

    A waist-high maintenance channel runs beside the main passage. Its rusted grates can support one person at a time, but the current below can sweep away anyone who falls.

  • Outside rooms 1 and 2

    A row of small brass bells hangs from wire across the ceiling. The bells are connected to the guard posts and ring if disturbed.

  • Between rooms 8 and 14

    The walls here bear a slimy handprint trail that ends at a blank stretch of masonry. Pressing the largest print reveals a narrow crawlspace.

  • Near rooms 12 and 19

    A burst pipe fills this sloping corridor ankle-deep with warm water. Something large occasionally bumps the underside of the grating.

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