Adventure Summary: A one-session survival horror adventure for four to five 6th-level characters. During the reservoir’s lowest tide in decades, a stone road rises from the water and stranded pilgrims appear at its far shrine. The party must lead them home before the road sinks and a drowned ferryman completes his final crossing.
Hollowmere Lantern Saga: Part 2 of 4. This adventure stands alone. Previously: The Lanterns That Know Your Name. The saga continues with The House Beneath the Reservoir.
Overview
At predawn, Hollowmere Reservoir retreats and exposes the Sunken Causeway, a road last walked on the night the valley drowned. Twenty living pilgrims stand at Saint Orra’s Shrine on the far shore. They entered the chapel yesterday and emerged forty years in the past according to every clock they carry.
The road will sink at sunrise. Toma Reed asks the party to escort the pilgrims across, but a spectral ferryman is collecting a toll of breath from every traveler. The heroes must manage the rising water, repair the Broken Span, and discover why Sister Ysabet alone remembers the original flood.
Background
Saint Orra’s order guided travelers through the lower valley. On the flood night, the order’s ferryman, Cadoc Vale, tried to rescue a final group after officials sealed the bridge. His overloaded boat capsized. The erased memorial trapped Cadoc in an endless crossing, and the reappearance of those names has called his passengers home.
Standalone hook: Hollowmere pays 800 gp to return the stranded pilgrims before sunrise. Saga hook: Mara’s restored ledger predicts the causeway’s return and identifies Ysabet’s medallion as the key to a manor hidden beneath the reservoir. Prior success grants one automatic route success, but is not required.
Characters
- Toma Reed: A young marsh guide masking terror with precise route notes. He knows every modern current but none of the drowned road’s old customs.
- Sister Ysabet: The oldest pilgrim, though she appears thirty. She carries Saint Orra’s medallion and remembers the flood as if it happened yesterday.
- Cadoc Vale: The drowned ferryman. He believes no soul may leave his route without paying the breath he lost.
- Pella and Rin: Frightened siblings among the pilgrims. Keeping them together prevents panic and reveals the hymn that calms the procession.
Setting
The Sunken Causeway winds two miles through black water. Its Bell Cairn, Ferryman’s Hut, Chapel Shoal, Broken Span, Dry Tower, and Saint Orra’s Shrine form six scenes. The water begins ankle-deep and rises one step after each scene.
Track six Tide steps: dry, ankle, knee, waist, chest, and submerged. A major failure advances the Tide an extra step. Characters may spend ten minutes and one spell slot, Hit Die, or useful tool proficiency to prevent one extra advance. The route never vanishes without a playable escape option.
Plot Outline
The party reaches the stranded pilgrims, organizes the column, learns the road’s toll custom, rings the Bell Cairn, shelters at the Ferryman’s Hut, repairs the Broken Span, and confronts Cadoc as the road sinks. The travelers can survive through force, a substitute toll, the pilgrims’ hymn, or proof that Cadoc’s final passengers reached a remembered shore.
1. The Shrine Out of Time
The party crosses by skiff to Saint Orra’s Shrine. Three DC 14 Arcana, Religion, or Investigation successes establish that the pilgrims are living people displaced in time, not undead. Failure advances the Tide, but Ysabet still explains that the procession appears whenever someone rings the Bell Cairn without offering a breath.
2. Organize the Crossing
Divide the pilgrims into three groups: the swift, the burdened, and the frightened. Assigning a hero or capable pilgrim to each group requires DC 13 Medicine, Persuasion, Survival, or land vehicles checks. Two successes preserve order. A failure means Pella runs toward a voice in the water and must be retrieved before two Drowned Pilgrims surround her.
3. The Bell Cairn
The cairn bell is cracked. Ringing it safely requires a DC 14 Religion or Performance check while another character braces the frame with DC 14 Athletics or mason’s tools. Success reveals Cadoc’s ferry under the surface and pauses the Tide for one scene. Failure summons two Causeway Leeches and causes the bell to toll each character’s name.
4. Ferryman’s Hut
A dry ledger lists breath as a symbolic promise to return, not a literal sacrifice. Cadoc’s ghost appears and demands one breath from every traveler. A DC 15 Insight check reveals he is repeating an order carved beneath the desk. Scraping away the forged order or offering a shared vow lets half the column pass without a toll. Fighting him here only disperses him until the Broken Span.
5. Repair the Broken Span
The middle arch has collapsed into ten feet of rushing water. The party needs four successes before two failures using DC 15 Athletics, Acrobatics, Survival, mason’s tools, or a suitable spell. Pilgrims hold ropes and grant one automatic success if their morale is intact. Each failure advances the Tide and exposes one traveler to a Causeway Leech.
6. Cadoc’s Last Crossing
Cadoc arrives in a spectral ferry with six Drowned Pilgrims. At initiative count 20, a wave crosses the road; creatures not holding a rope make a DC 15 Strength save or move 15 feet toward deep water. The party wins by reducing Cadoc to 15 hit points, ringing the cairn bell three times with DC 15 actions, or earning three DC 15 Religion or Persuasion successes while Ysabet leads the homecoming hymn. Cadoc accepts the truth that his passengers survived in memory and carries the dead away instead.
7. Resolution
The living pilgrims reach West Gate as the causeway sinks. Cadoc’s ferry becomes a single harmless ripple if released, and the rescued families establish a new hospice. Ysabet gives the party her Breathglass Rosary. Its medallion points toward a drowned manor, opening the next saga chapter without leaving this rescue unresolved.
NPCs and Monsters
| NPC or Monster | Statistics | Key Abilities and Table Notes |
|---|---|---|
| Toma Reed | Medium humanoid; AC 14, HP 38, speed 30 ft. | Survival +7 and water vehicles +6. As a reaction, he lets one ally reroll a failed route or current check. He protects the slowest pilgrims first. |
| Sister Ysabet | Medium humanoid; AC 12, HP 33, speed 30 ft. | Religion +7, Medicine +6. Her homecoming hymn grants one creature advantage on a save against fear or forced movement each round. |
| Cadoc Vale | Medium undead; AC 16, HP 92, fly 30 ft. (hover). | Ferry Hook +7 deals 2d6 + 4 cold and pulls 10 feet. Breath Toll, DC 15 Constitution save, prevents reactions and speech for one round. He yields at 15 HP. |
| Drowned Pilgrim | Medium undead; AC 13, HP 30, speed 25 ft., swim 30 ft. | Waterlogged Staff +4 deals 1d8 + 2 and reduces speed by 10 feet. A spoken homecoming verse stuns one pilgrim until the end of its next turn. |
| Causeway Leech | Small monstrosity; AC 14, HP 24, swim 30 ft. | Bite +5 deals 1d6 + 3 piercing and attaches. An attached leech deals 1d6 necrotic at the start of its turn until removed with an action and DC 13 Medicine. |
Rewards
- 800 gp from Hollowmere, plus a pearl reliquary worth 200 gp if all twenty pilgrims survive.
- Breathglass Rosary: The wearer can hold their breath for one hour. Once per dawn as a reaction, the wearer grants up to six creatures within 20 feet ten minutes of breathable air.
- Cadoc’s Passage: If released, his ferry safely carries the party across one haunted body of water when called by the homecoming hymn.
Scaling the Adventure
For a 5th-level party, use four Drowned Pilgrims in the finale and reduce Cadoc to 76 hit points. For a 7th-level party, add two pilgrims at the Bell Cairn and increase the wave save DC to 16. For a shorter session, begin with the column organized and place the toll ledger at the Bell Cairn.
Drowned-Road-Horror-Themed Table Gear
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- Stone causeway terrain tiles. Build a route that visibly disappears as the Tide tracker advances.
- Clear bubble glass beads. Pass a physical bead when a pilgrim receives protection or spends their breath.
- Portable low fog effect. Add a thin bank of mist around the Bell Cairn and Cadoc’s final crossing.