Troll WarrenHidden VaultPuzzle RoomSetpiece
A 15-ft-wide circular chamber behind a curtain of mushroom-flesh in the deepest cell of Old Mawg's warren. The walls are slick with sweating mud and the air smells of copper and old iron. The chamber is a vertical shaft 80 ft tall — a natural rock chimney plugged at the top by a heavy stone disc the size of a millstone. No light works in here except as described below. The puzzle has three elements — the goat and the lantern, the thirteen stones, and the climb to the sky — and a trap built into element two: once the thirteenth stone goes into its niche, a slab slams down across the entrance and the chamber is sealed. Now the water matters.
The party pushes through the mushroom-curtain into a black, dripping space. Echo-bounce tells them the room is taller than it is wide. The floor is a low bone-pile drifted up against the far wall. The air is wet, metallic, and very still. Bring up the smell first — let them ask for light second.
By feel, the party finds a heavy brass lantern hanging from a corroded chain at the chamber's center, at chest height. Its reservoir is empty. Directly above it, swinging slowly on a second chain, is a long-dead goat, hung by its hind legs, throat opened by some old knife. A thin copper funnel is wired under its throat, angled to drip into the lantern's reservoir. Old, clotted blood crusts the funnel and the lantern's lip.
The lantern will only burn on blood. Any blood — the goat's, a PC's, whatever is in the funnel — will fill the reservoir and the lantern will light at a touch (no flint, no spark).
From the goat: the funnel still holds enough old, congealed blood to fill the reservoir once. Lit on goat-blood, the lantern burns smoky and brown for 30 minutes and casts dim light in a 15-ft radius. This is the only flame that survives in the chamber.
From a PC: a creature spends an Action and 1d4 HP of their own blood to refill the reservoir. PC-blood burns clean and bright for 10 minutes per HP donated, dim light, 15-ft radius.
The lantern will be the only working light source until the party leaves. They will need it for what comes next — and the goat's blood is enough to get started.
Once the lantern is lit, the party can see what's around them. The wall of the chamber is ringed with thirteen small niches at chest height, evenly spaced. Above each niche, the stone has been carved with a shallow sigil — but the sigils are not visible. The wall above the niches looks like blank, sweating mud.
The etchings only appear under fresh blood. Goat-blood (old, clotted) will not bring them out. A PC who tries — and someone will try — sees the smear soak into the mud and disappear. Read the goat-blood failure clearly so the table feels the shape of the puzzle. They have to bleed for themselves, or fail the test.
Cost: a creature spends an Action and 5 HP of their own blood to smear it across the wall above the niches. All thirteen sigils glow faintly — a steady, blood-warm red — for 10 minutes, then fade. Refreshing them takes another 5 HP. This is the puzzle's clock. Have a timer ready.
At the chamber's lip sits a shallow stone bowl. In it: thirteen river-stones, each clearly distinct — different colors, weights, markings, shapes. They are heavy for their size.
The stones are weights. Each niche is a small pressure-plate. Each stone fits any niche, but only one niche is correct for each stone — the one whose sigil names it. When the right stone goes into its niche, the pressure-plate seats; when the wrong stone goes in, the plate sits crooked and water begins to seep in around its edges from somewhere behind the wall.
| Sigil (above the niche) | The stone it names |
|---|---|
| A hand cupped, begging | The bone-white stone, knuckled at one end |
| A flat lid, three rings | The leaden-grey stone, faintly runed |
| A drop of blood | The rust-red stone, mire-colored |
| A root, twisted | The gnarled stone shaped like a finger |
| An eye, half-lidded | The polished black stone with a yellow vein |
| A mountain with a face | The mossy stone, lichen on one side |
| A coin, broken | The split stone, sharp on one edge |
| A candle, smoking | The soot-blackened flat stone |
| A map's edge, torn | The stone etched with false rivers |
| A heart | The heart-shaped stone, pale pink |
| A bowl with ants | The pitted stone, small holes across its face |
| A wolf's open jaw | The fanged-looking stone, jagged at one end |
| The sky, with one white speck | The round black stone with a single white speck |
Run-it-fast option: if your table is slow, let each stone glow faintly the color/shape of its matching sigil when the etchings are fresh — players just have to look carefully and match. Run-it-hard option: keep it strict — the sigil names the stone in image only, and the table has to read each one.
For every wrong stone currently seated, water seeps in around the niche's edge at a rate of 1 inch per 10 minutes of flood across the chamber floor.
With the entrance open, the water runs out under the mushroom-curtain and the flood never rises past a damp boot. Players will not feel the urgency yet. This is intentional. They will be testing stones, swapping them around, watching for which niches stop leaking and which keep leaking. Let them work.
The moment the thirteenth stone is placed in a niche — any niche, correct or not — a heavy slab of stone slams down across the chamber's only entrance with a crack that throws dust into the air. The mushroom-curtain is gone behind a foot of granite. The chamber is sealed. The lantern jumps on its chain. The goat sways.
This is the moment the puzzle becomes a trap. Until now the room was patient — they could place, listen, swap, listen, learn. Now the water has nowhere to go and the door doesn't open until every niche is correct. Drop the read-aloud below and roll the first leak.
From the slam onward, the water from any wrong niche has nowhere to drain. Track it as a simple flood clock:
Every 10 minutes of in-fiction time, the water rises by 1 inch for each wrong stone currently seated. The clock fills accordingly.
| Depth | Effect |
|---|---|
| Ankle (6 in) | Difficult terrain for Small/Medium creatures. |
| Knee (1.5 ft) | Speed halved. Stones in the bowl at chamber's lip are now under water — Investigation DC 12 to fish them out. |
| Waist (3 ft) | Disadvantage on Strength checks not involving swimming. The lantern's bottom edge is wet — protect it or it goes out. |
| Chest (4.5 ft) | Light armor floats; Medium/Heavy must roll DC 12 Athletics to keep feet. Spellcasting V components fine; S components require a free hand above water. |
| Submerged (6 ft+) | Holding breath rules. Lantern is out. The room is pitch dark. This is the death state. Aim for the table never to reach this. |
This is why the etchings' 10-minute window is the right pressure. One refresh of the sigils = one tick of the flood clock = one window to swap stones and fix the leaks. A clever party will refresh, identify wrong placements, swap, refresh again, fix more, and keep the water below ankle. A panicked party will burn HP on the lantern instead of the etchings and drown.
When all 13 stones are seated correctly, every plate clicks home in the same instant. The leaks stop. The chamber goes quiet for a full breath. Then —
The chimney narrows from 15 ft to 6 ft at its midpoint — the throat — and the water sluices down it the whole way, throwing spray. The rungs are old iron, cold, spaced for a creature taller than human, slick with running river-water and slime.
Down at the bottom, the chamber keeps filling. Every round a PC is still climbing, the water down there rises a foot. A PC who fails badly and drops back into the chamber may find themselves swimming. This is the cost of being slow.
At the top of the chimney is a small circular ledge under a fissure of open sky, lit by real moonlight. The river itself is a wide, slow flow a few feet to one side, beyond a stone lip the cascade was pouring over. The ledge is dry. The party can breathe again. They have touched the sky.
The ledge holds Old Mawg's hidden trove, in a moss-grown stone cradle.