GM Notes
Beneath the Razored Labyrinth
GM-Only Campaign Notes
Core Truth
The sinkhole beneath Kridorfrost is not natural. It was triggered by renewed excavation far below: a project to complete an ancient connector tunnel beneath the Castrovin basin.
The obsidian fragments found in the rubble come from Black Glass Peak, where organized pirates are harvesting the material for a dark purpose.
The campaign begins as a bridge disaster, becomes a smuggling investigation, then expands into a sea expedition and finally a Darklands descent.
Full Adventure Summary
The Castrovin Sea is vast, storm-scoured, and treacherous. Most sailors avoid the deeper waters and the jagged volcanic maze known as the Razored Labyrinth.
The ancient Bridge of Kridorfrost stands as the only crossing of the Noyrus River for a hundred miles. When a sinkhole opens beneath the bridge’s lower supports, workers vanish into flooded tunnels and the town’s fragile prosperity begins to crumble.
The earliest problems appear practical: missing workers, a collapsing bridge, strange obsidian fragments, and rumors of organized smugglers using the tunnels.
Soon the investigation points south to Kridorn, where pirate brokers and salvage crews know more than they admit, and to the sea-stack trading post of Citadel Allatro.
What appears to be a local accident becomes something larger: a Darklands-connected conspiracy using the Razored Labyrinth as a surface breach.
By mid-campaign, the party leaves the river behind and ventures across the Castrovin Sea through sea-stack mazes, submerged ruins, and lost Ninshabur.
They uncover evidence of an older power beneath the Castrovin basin, one tied to the ancient cyclopean empire and possibly to Spawn-like horrors beneath the earth.
The final arc descends beneath the Razored Labyrinth into dry volcanic caverns and Darklands tunnels. The heroes must decide whether to seal the breach, sabotage the spawning chambers, or expose the conspiracy before abyssal forces gain a permanent foothold.
Major Story Arcs
| Level Range | Arc | Focus | End State |
|---|---|---|---|
| 1–3 | The Sinkhole Beneath Kridorfrost | Bridge inspection, rescue, flooded tunnels, smugglers' trail | The party learns the collapse was not accidental; obsidian and organized activity point to a larger plot. |
| 4–6 | Kridorn and the Obsidian Trail | Port intrigue, pirate networks, locathah diplomacy, Black Glass Peak | The PCs discover that pirates are harvesting obsidian for a Darklands-connected intermediary. |
| 7–9 | Lost Ninshabur and the Sea-Stack Map | Ancient lore, underwater carvings, Keleshite patrons, map fragments | The party recovers the navigational route through the Razored Labyrinth and learns of the ancient connector tunnel. |
| 10–12 | Beneath the Razored Labyrinth | Submersible expedition, sea-stack navigation, abyssal descent, spawning chambers | The heroes confront Vhargul Soot-Crowned, sabotage the spawning ground, and collapse the tunnel. |
Adventure Structure Overview
| Arc | Primary Location | Key Factions | Major Set Piece |
|---|---|---|---|
| Sinkhole Beneath Kridorfrost | Kridorfrost & the Bridge | Bridge-wardens, smugglers, local engineers | Descent into the flooded tunnels |
| Kridorn and the Obsidian Trail | Kridorn, Citadel Allatro | Pirate brokers, locathah traders, Keleshite navy | Raid on Black Glass Peak |
| Lost Ninshabur | Ninshabur ruins, sea-stack route | Keleshite antiquarians, undead guardians, locathah shamans | Recovery of the Flayed Map fragment |
| Beneath the Labyrinth | Razored Labyrinth, dry Darklands | Vhargul's crew, Spawn-like defenders, abyssal cultists | Assault on the spawning chambers |
Faction Quick Reference
| Faction | Goal | Attitude Toward Party |
|---|---|---|
| Kridorfrost Bridge-Wardens | Secure the bridge, protect trade | Allies if party helps stabilize the structure |
| Kridorn Pirate Brokers | Profit from obsidian and smuggling | Hostile or mercenary; can be bribed |
| Locathah of Citadel Allatro | Guard sea-stack carvings and Black Glass Peak | Wary but open to negotiation |
| Keleshite Navy | Maintain control, suppress piracy | Suspicious; may view party as rivals |
| Vhargul's Darklands Crew | Complete the connector tunnel and prepare the spawning ground | Always hostile |
Random Encounters by Region
| Region | d8 Encounter | Suggested Level |
|---|---|---|
| Kridorfrost / Bridge | 1. Sinkhole patrol · 2. Collapsing scaffold · 3. Smuggler cache · 4. River-drake · 5. Cyclopean carving glow · 6. Lost worker · 7. Obsidian shard trap · 8. Tunnel flooding | 1–3 |
| Kridorn / Coast | 1. Pirate press-gang · 2. Locathah trader · 3. Storm surge · 4. Merrow scout · 5. Salvage operation · 6. Keleshite patrol · 7. Black Glass Peak raid · 8. Sea-cat pride | 4–6 |
| Ninshabur Ruins | 1. Undead guardians · 2. Trap-infested vault · 3. Treasure hunter camp · 4. Sandstorm · 5. Cyclopean inscription · 6. Flayed Map fragment · 7. Collapsing floor · 8. Ancient seal | 7–9 |
| Razored Labyrinth / Darklands | 1. Submerged sea-stack · 2. Spawn-like guardian · 3. Volcanic vent · 4. Flooded chamber · 5. Obsidian lattice · 6. Scrag ambush · 7. Pressure door · 8. Vhargul's patrol | 10–12 |