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Deep dungeon that goes to the underdark. The party is locating and escorting a supplier who has yet to return back with supplies to make important enchanted oil and wicks for lanterns that are designed to keep beasts off the streets at night. Without this supplier and supplies, less light for the town spells certain disaster for its citizens. · Medium · Medium

Lantern-Throne Below

When the lanterns fail above, the dark below comes collecting.
Rooms
7
Foes
19, CR 1/2 to 5
Traps
7
Treasure
1,580 gp
1234567Entrance
Select a room on the plan to open it.

The party is in

1. Broken Customs Hall

Seen

Something wanders by

At a glance

The threat

A cunning underdark broker, part fungal mystic and part slaver, has turned the old customs vault into a choke point over the town’s lamp supply.

Wandering monsters (1d4)

  1. 1

    1d4+2× Oil-Slick Cave LeechesCR 1/2

    When: When the party makes loud noises, spills oil, or rests in a corridor with exposed fuel stores.Small, pale tunnel vermin attracted to oil, heat, and blood. They probe campfires and fallen enemies alike.
  2. 2

    1d2× Underdark Scout PairCR 1

    When: When the party crosses between guarded rooms or lingers near the sealed checkpoint.Masked scouts bearing hooked knives and dim blue lanterns, sent to confirm intruders and report upward.
  3. 3

    Spore-Touched ThrallCR 2

    When: When wards are disrupted or the party uses fire in a chamber linked to the pit.A lone fungal thrall with a cracked helm and glowing spores leaking from its joints.
  4. 4

    1d3× Dusk PatrolCR 3

    When: After combat in or , or if the final door is forced loudly.A heavy patrol from below, sent to secure the boss chamber if alarms sound.

Rooms

7
1

Broken Customs Hall

2 foes1 traptreasuresecret

What they see

Read aloud

A broken customs hall opens under a cracked arch, with faded lantern sigils on the floor and a watch brazier that still smolders in the center. The air is cooler here, but the way forward is blocked by a half-closed iron portcullis and fresh drag marks leading deeper inside.

Features

  • Cracked lantern sigils
  • Half-raised iron portcullis
  • Smoldering watch brazier
  • Notice board with old shipping tags

What the GM knows

Monsters

2× Undercrypt LookoutsCR 1/2

Lean tunnel lookouts in patched hide armor who try to sound an alarm rather than fight fairly.Tactics. They fight from behind the portcullis, hurling javelins and retreating to ring a bell if pressed.

Traps

Customs Spear TrapDC 13 piercing

A rusted drop-spear mounted above the gate fires when the portcullis is forced without first lifting the counterweight pin.Disarm. Lift the counterweight pin from the side wall and jam the release gear with a crowbar or thief tools.

Treasure

Sealed Oil Flask Bundle40 gp

Three intact lantern oil flasks wrapped in wax cloth, enough for a short-term boost to the town supply.

Warden Token15 gp

A stamped customs token that can open one later locked gate in the dungeon if matched correctly.
Room secrets · GM only

Notes

Entrance room. Let the players find signs that the supplier passed through recently, including a dropped seal stamp or oil-smeared ledger scrap.

3 doors: W (normal), N (normal), S (locked)

The place

What it is

This is a buried checkpoint of stone, fungus, and old warding built to control passage into the underdark below.

Atmosphere

Cold wet stone and old lamp smoke cling to every surface.

The threat

A cunning underdark broker, part fungal mystic and part slaver, has turned the old customs vault into a choke point over the town’s lamp supply.

History

The complex began as a surface watch-post and customs vault built over a natural sinkhole that opened into the underdark.

Rumors

1d5
Roll a rumor

  1. 1The old customs vault below the cistern was sealed because something down there learned how to bargain with thieves.
  2. 2The missing supplier was seen carrying a chest of enchanted oil, then followed by figures with fungus lamps.
  3. 3Town watch swear the night beasts have grown bolder since the lantern towers began sputtering.
  4. 4There is a secret way back to the surface in the old support shafts, but only if you know which wall was bricked up last.
  5. 5Someone in the underdark wants the lamp formula intact, not destroyed.

Plot hooks

4
Rescue and recoveryThe Light Runs LowThe town’s night-watch begs the party to find the missing supplier and recover enough enchanted oil and wick stock to keep the streets lit through the week.From: Captain Edda Vane, militia captainReward: 300 gp, a case of blessed lantern oil, and legal favors from the town council
InvestigationLedger in the DarkA frightened apprentice reveals that the supplier sent one last message mentioning a checkpoint below the old cistern and a keeper who bargains in lamps.From: Mirel, lantern apprenticeReward: The supplier’s ledger of contacts and a minor charm against darkvision-based ambushes
SabotageBreak the WardThe town’s largest oil lamp shrine is failing, and the clerics want the boss chamber’s hidden valve or ward-heart disabled before the underdark can retaliate.From: Sister Halwen, shrine keeperReward: Blessing against darkness effects and 200 gp in temple donations
ExplorationThe Second Way UpAn old tunnel map suggests a secret return route to the surface that could become a smuggler’s path if cleared and controlled.From: Bram the ferryman, retired tunnel scoutReward: Claim to a hidden shortcut, plus a cache of old salvage

Corridors

4

  • Upper approach corridors between and

    Rust-streaked wall braziers burn with a pale blue flame that gutters when living creatures pass, as if reacting to breath or heat.

  • Mid-level passages near and

    Collapsed cart tracks and drag marks run along the floor, showing where heavy barrels of oil and crates of wick bundles were hauled deeper in.

  • Hidden in the walls near and

    A narrow maintenance channel behind the stonework leaks warm air and distant chanting from the boss chamber.

  • Lower corridor before room-7

    Patches of phosphorescent fungus line the final descent, casting a sickly glow on carved warning sigils half-scratched out by recent hands.

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