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The Drowned Drain

Beneath the ruined streets, foul water carries the Dragon Below's dreams.

22 rooms✦sewer✦medium

Beneath a ruin shanty town, the city's forgotten sewers have become a drowned green maze. A sickly swamp has spread through broken channels, feeding on curses leaking upward from the dragon buried below the city. Kobolds, ratkin, oozes, and warped plants fight over the flooded ruins.

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Warm, wet air presses through the tunnels, thick with rot, stagnant water, and the sour stink of kobold refuse. Green mold glows faintly beneath the waterline, while insects buzz in the dark and distant pipes groan whenever the swamp shifts. Every few minutes, something splashes beyond the reach of the party's light.

☠ Threat

The deepest chamber houses Varkul, a young dragon-blooded kobold oracle who believes the Dragon Below speaks through the swamp. His body is swollen with green-black scales and his magic spreads the curse through water, plants, and ooze. He commands the remaining kobolds and ratkin while preparing to break the ancient seal in room 13.

History

The sewer was built beneath the old city by engineers who discovered a buried draconic temple while digging its deepest channels. Rather than destroy the ruin, they used the sewer's flow to feed a binding seal and hid the truth from later generations. When the city fell into ruin, kobolds moved into the tunnels and maintained the seal until cursed water poisoned their minds.

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Encounter Table

CR
1/8CR
Moss Ratsx1d6

A pack of hungry rats with moss-covered hides and glowing green eyes.

1/4CR
Ratkin Patrolx1d4

Cursed ratkin scavengers carrying hooks, stolen keys, and bundles of damp cloth.

1/4CR
Crawling Bloodrootx1

A crawling mass of carnivorous vines and pale flowers that has detached from the swamp floor.

1/2CR
Drifting Sewer Oozex1

A wobbling gray-green ooze carrying coins, bones, and fragments of sewer masonry.

Rumours & Whispers

1

The green swamp appeared overnight after a deep rumble beneath the ruined district.

2

Kobolds are dragging prisoners into the sewers and feeding them to plants with teeth.

3

An old priest claims clean water still flows somewhere below, guarded by the ghosts of city engineers.

4

Ratkin have been seen carrying silver keys toward the collapsed ruins.

5

Something under the city dreams loudly enough to make the drains run uphill.

Quest Hooks

1
The Child Beneath the BoardsRescue

Quest giver: Mara Venn, a scrap dealer and worried neighbor.

A child from the shanty town vanished after following a trail of glowing insects toward a broken sewer grate. The trail leads through rooms 0, 1, and 5, where the child is trapped among cursed prisoners.

20 gp, salvaged tools, and free lodging in the shanty town.

2
Bitter WaterInvestigation

Quest giver: Brother Caldus, a weary street priest.

The town's wells have turned bitter and green. The party must find the source of the contamination and recover a clean sample from a shrine basin in room 18.

A healer's kit, three antitoxin doses, and a blessing that grants advantage on one save against poison.

3
The Seal KeepersDiplomacy

Quest giver: Skritch, a frightened kobold hiding in a chimney.

Kobold survivors claim their kin are being forced to serve a sleeping dragon. If the party reaches the shrines and repairs the seal, some of the cursed kobolds may become allies.

A kobold guide, a pouch of common gemstones, and safe passage through the upper tunnels.

4
Relics in the RotExploration

Quest giver: Ilyra Sorn, an ambitious antiquarian.

A ruined noble house wants the ancient relics beneath the city recovered before scavengers find them. Their map identifies rooms 10, 19, and 21 but omits the traps and the living swamp.

35 gp and a choice of one common adventuring item.

Corridor Notes

Along most corridors, especially between rooms 2, 5, and 10.

Black water fills the lower channels, hiding rat-sized holes, loose stones, and pale leeches that cling to boots.

Near rooms 3, 7, 13, and 17.

Bundles of sewer roots have broken through the masonry, forming curtains that conceal movement and narrow passages.

Around locked doors and crossroads near rooms 1, 6, and 10.

Small kobold warning marks appear in dried mud, showing symbols for poison, hungry plants, and the dragon below.

At the junctions leading toward rooms 13, 16, and 21.

Collapsed pipe vents exhale warm, mineral-scented vapor that briefly carries distant whispers and the scrape of claws.

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