The Singing Path and the Obsidian Vault
The Singing Path and the Obsidian Vault
After nursing a wounded young phoenix back to health, the party witnesses the creature fall into a fevered dream, whispering of "the singing path" and ancient runes — a phrase that drains the color from the face of Mira Stonehollow, the elder of the underground village of Deepwick. She reveals the legend: the Singing Path is a trail of resonant rune-stones that leads through the cave network's most dangerous biomes to the Obsidian Vault, a sealed chamber said to contain the answers — and the chains — of a dark force that once preyed upon all the underground villages. The phoenix's dream is not random. Something in the Vault is stirring, and its magical lure, long thought dormant, has begun to pulse again, drawing restless creatures toward the deepest caverns. The party must follow the Singing Path, decode the runes, and discover whether the Vault is still sealed — before whatever sleeps inside wakes up fully.
Read Aloud
You are gathered around a shallow stone basin filled with warm ash in the hearthroom of Deepwick, the underground village carved into amber-veined rock. The young phoenix rests within — its ember-bright feathers have dimmed to a smouldering copper, bandaged where a cave basilisk's claw raked it. The air smells of burnt cinnamon and damp stone. Then, without warning, its beak opens and a voice spills out that does not belong to any bird — low, rhythmic, hypnotic: "The singing path, the singing path — it will tell of the runes and the pact. The singing path, the singing path." Across the room, you hear a clay cup shatter on the floor. Mira Stonehollow, the village elder, stands motionless, her knuckles white, her face the color of pale limestone.
Description
The party is in Deepwick's hearthroom after rescuing and tending to a young phoenix they found injured in the mid-cavern biome. The phoenix is sleeping but begins to dream aloud. The phrase it recites — "the singing path" — is a piece of frightening folklore known to every elder in the underground network. Mira Stonehollow recognizes it immediately and is visibly terrified. She will explain the legend of the Singing Path and the Obsidian Vault to the party, but only after she has composed herself and sworn them to secrecy from the younger villagers. On the walls of the hearthroom, sharp-eyed players can spot faint carvings half-painted over with white clay — angular rune shapes that vaguely match the ones the phoenix described.
DM Notes
DC 12 Wisdom (Perception): A player notices the painted-over rune carvings on the hearthroom walls — someone tried to erase them long ago. DC 14 Intelligence (History) or (Arcana): A character recognizes the syllabic pattern of the phoenix's chant as a mnemonic binding-verse, a type used in ancient pact magic to encode a location. DC 10 Charisma (Persuasion or Insight): Mira is clearly hiding something beyond fear — she feels guilty, as if her own people played a role in whatever was sealed away. Allow the Bard-adjacent Rogue or the Paladin's Aura to create social openings. If players press her too hard too fast, she shuts down; let the Wizard's Arcana check open a more academic angle that she responds to better. The phoenix does not wake during this scene regardless of noise — it is deep in a magical dream state.
Read Aloud
Mira leads you away from the others into a low side-passage that smells of iron and old wax. She holds her lantern up to a section of wall and begins scraping away a thick layer of grey mortar with her thumbnail. Beneath it, carved directly into the cavern rock in thin precise lines, is a map — not of roads or rivers, but of caves, biomes marked with pictographs: a ripple for the flooded grottos, a flame for the magma vents, a tangle of roots for the fungal forest. At the map's far edge, where the lines converge, is a single solid black rectangle etched so deeply the shadow inside it looks like a hole. "The Obsidian Vault," she says, and her voice drops to barely a breath. "We were told it was sealed. We were told nothing could hear it anymore." She turns to you. "The lure — the magical beacon the Vault uses to call in creatures — we thought it had gone quiet. But if the phoenix dreamed of the path..." She cannot finish the sentence.
Description
Mira reveals that the Obsidian Vault is a sealed chamber at the heart of the deepest cavern system. Generations ago, the underground village network made a pact — the details of which are murky even to her — with a force they called the Hollow Choir, binding it inside the Vault in exchange for peace. The magical lure was the Vault's tool: a beacon that drew wild creatures to it, keeping them away from the villages. But if the lure is reactivating, it means something inside the Vault is waking. Mira gives the party the map (a rubbing she makes on linen) and explains that the Singing Path is a sequence of rune-stones placed throughout the cave biomes — they emit a harmonic hum that guided initiates to the Vault. She does not know what the runes say, only that they must be read in order. She begs the party to investigate but not to open the Vault — only to confirm whether the seal still holds.
DM Notes
This is the primary quest-delivery scene. Mira hands the party a linen map rubbing. DC 13 Intelligence (Arcana): The Hollow Choir is an entity or collective consciousness of sound-based origin — possibly an aberration or ancient bound demon. DC 15 Intelligence (History): The pact described matches historical records of "Resonant Bindings," a lost magical tradition that used harmonic frequency rather than written text to enforce magical contracts. DC 12 Insight on Mira: She is not telling the whole truth about the pact — she knows more than she is saying about what her ancestors gave the Hollow Choir in exchange for the peace. This can be a moral thread the Paladin latches onto. Place a subtle detail in the map — one of the biome markers is drawn in a different, shakier hand than the others, suggesting it was added later in fear.
Read Aloud
The passage opens without warning into a cathedral of bioluminescence. Mushrooms three times your height crowd the cavern floor in rings and spirals, their caps pulsing with slow blue-green light that shifts like breathing. Threads of mycelium hang between them like cobwebs made of cold starlight, and the air is thick and spore-sweet, clinging to the back of your throat. Near the center of this fungal forest, half-swallowed by a ring of cap-mushrooms, stands a column of dark stone about four feet high — and even from here you can hear it: a faint, pure, single musical note resonating from deep inside the rock, like a tuning fork that has never been allowed to stop. Crawling over the base of the rune-stone and through the nearest mushroom ring are a half-dozen creatures — and they are not behaving naturally. They move in slow, deliberate circles around the stone, as if caught in something they cannot name.
Description
This is the first biome the party passes through on the Singing Path: the Fungal Forest, a cavern dense with enormous bioluminescent mushrooms. The first rune-stone hums a single sustained note and is already attracting creatures — a symptom of the lure reactivating. The rune-stone bears three carved symbols. A successful Arcana check reveals they translate loosely as "Voice, Hunger, Bound." The creatures circling it are gelatinous in nature, drawn by the vibration. The Rogue can notice tracks suggesting larger creatures have been here recently and moved deeper — following the pull of the lure further in. This encounter takes place here.
DM Notes
DC 13 Intelligence (Arcana): The rune-stone inscription reads "Voice, Hunger, Bound" — the first fragment of the pact text. The party should be encouraged to copy or rub the runes. DC 15 Wisdom (Perception): The Rogue specifically can spot, on a 12 or higher with Expertise, that a much larger creature's tracks lead deeper into the caves — something big was here recently and continued inward. DC 14 Intelligence (Nature): The creatures circling the stone are not aggressive unless disturbed — the magical hum has put them in a trance-like orbit. Approaching the stone without disrupting them requires a DC 13 Dexterity (Stealth) check. Failing it breaks the trance and triggers combat. The mushroom terrain provides half cover behind large caps (a detail the Rogue should exploit for Sneak Attack positioning).
Read Aloud
The fungal forest gives way to the sound of water before you see any of it — a low constant rushing that echoes from every direction at once. Then the floor drops away and you stand at the edge of a vast flooded grotto: black water shot through with mineral veins of pale rose and white, reflecting your torchlight back at you in fractured pieces. Stepping-stone platforms of natural rock jut from the surface in an irregular path. Across the widest channel, anchored to a submerged column of rock that rises just above the waterline, is the second rune-stone — its hum lower than the first, a different note, and when it reaches your ears it feels less like sound and more like pressure behind the eyes. Something moves beneath the surface of the water. Not one thing. Several.
Description
The Flooded Grottos are a partially submerged cavern biome with stepping stones, shallow channels, and deeper pools that drop into pitch-black darkness. The second rune-stone stands on a natural column in the middle of the widest channel. This scene is a skill challenge — the party must navigate to the rune-stone without triggering the creatures in the water (Chuuls drawn by the lure's pulse) and then read the rune inscription. The runes read "Silence, Depths, Remember" — the second fragment. If combat breaks out here, the difficult terrain of stepping stones and water significantly advantages ranged attackers and the Fighter's ability to hold chokepoints.
DM Notes
Skill Challenge: Reaching the rune-stone safely. Three successes before three failures. Suggested checks: DC 12 Athletics (jumping between stones), DC 14 Stealth (moving quietly over the water), DC 13 Arcana (sensing the chuuls' connection to the lure and predicting their patrol pattern), DC 15 Animal Handling (attempting to soothe a chuul that surfaces). On three failures or if the party opts for combat, the Chuuls attack — use the encounter card. The Wizard should note that the pressure from the rune-stone's hum may require Concentration saves if they are hurt near it (DC 10 Constitution saving throw). DC 14 Arcana to read the rune-stone inscription: "Silence, Depths, Remember." Second fragment of the pact collected. The Fighter is ideal for holding a chokepoint on a narrow stepping-stone bridge if combat erupts.
Read Aloud
The Singing Path ends here, and the silence that replaces the rune-stones' hum is worse than any sound you have heard today. You stand before a wall of pure obsidian — not stone that happens to be black, but a surface so perfectly smooth it reflects your faces back at you like dark mirrors, slightly wrong, slightly delayed. Set into the obsidian at chest height are six recessed panels, each one carved with a symbol your party has now seen: Voice, Hunger, Bound, Silence, Depths, Remember. The seal glows — but not with one steady light. It pulses, and in the rhythm of that pulse you recognize the same beat as the rune-stones, the same beat as the phoenix's whispered chant. And there — along the very edge of the obsidian wall, hairline thin but unmistakable — a crack. The Vault is not fully sealed. Not anymore.
Description
The party arrives at the Obsidian Vault. The seal is cracked — not broken, but compromised. Through the crack seeps a barely audible sound: a chord of many voices layered over each other, beautiful and deeply wrong. This is the Hollow Choir. The six rune-fragments the party collected form the key sequence for the seal's diagnostic panel — pressing them in order does not open the Vault but causes the seal to display its status. A successful Arcana check reveals that the seal will hold for perhaps days or weeks at most before the crack widens. The party faces a critical decision: try to reinforce the seal with what they know (requiring the pact knowledge Mira withheld), go back to Mira to demand the full truth, or investigate the crack to understand what is leaking through — which risks drawing the attention of whatever is inside. The boss encounter of the session is here: a guardian that the pact created to protect the Vault from the outside, which has been driven half-mad by the leaking energy and now attacks anything that approaches.
DM Notes
This is the climax scene. Do not rush it — let players take in the visual and the weight of the decision. DC 15 Arcana: The pulsing of the seal matches a degrading harmonic binding — the crack is growing imperceptibly but continuously. DC 16 Arcana: The six rune-fragments, spoken aloud in sequence, can temporarily reinforce the crack as a stopgap — buying weeks, not a permanent solution. DC 14 Insight: The voices leaking through the crack are not screaming or violent — they are searching, tasting, as if learning something about the world outside. The boss guardian is a Flesh Golem reskinned as a "Resonance Warden" — a stone-and-crystal construct assembled from cave material, crackling with absorbed harmonic energy. Its "Lightning Absorption" becomes "Sonic Absorption" narratively: the rune-stone hums have empowered it, making it more dangerous the closer they got to the Vault. After the encounter, if the party uses the rune-fragments to seal the crack, award full XP and give them a meaningful choice to bring back to Mira. The Paladin's Divine Smite is highly effective here; the Wizard should avoid large AoE near the obsidian wall (risk of structural vibration — DC 14 Constitution save for creatures nearby if a spell of 3rd level or higher detonates within 10 feet of the crack).
Monsters
Tactics
The Ochre Jellies begin the encounter in a trance-orbit around the rune-stone and only become aggressive if the party moves within 10 feet of the stone or makes a failed Stealth check (DC 13). They fight by attempting to engulf the nearest creature. The Gelatinous Cube patrols a long mushroom corridor and becomes aggressive if any creature runs into its space fleeing the Jellies — a dangerous moment if the Fighter or Paladin retreats without looking. The Gelatinous Cube is nearly transparent in the bioluminescent light (DC 15 Perception to spot before entering its space). The Ochre Jellies split if struck by slashing or lightning damage, potentially creating two additional CR 1 Ochre Jellies — warn the Wizard player of this risk before the session as a built-in tension. The mushroom caps provide half cover for the Rogue seeking Sneak Attack opportunities but obstruct movement as difficult terrain between the ring-clusters.
Terrain
Dense fungal forest: clusters of massive mushroom caps provide half cover. Spaces between rings are difficult terrain due to thick mycelium webbing on the ground. The rune-stone stands in a 20-foot-diameter clear circle at the center. Bioluminescent spores drift throughout — any fire damage in the cavern (including Paladin's Divine Smite if it produces light-flash) causes a spore cloud that lightly obscures a 10-foot area until the start of the next round. Two mushroom columns can be toppled with a DC 14 Strength (Athletics) check, creating an improvised barrier of difficult terrain.
Monsters
Tactics
The two Chuuls begin submerged and surface on initiative 20 of the first round of combat — until then they are unseen beneath the opaque black water. They prioritize grappling and dragging targets into the deeper channels (marked on the DM's version of the map). A grappled creature pulled into a deep channel must succeed on a DC 12 Athletics check to avoid being pulled fully underwater on the Chuul's next turn. Submerged creatures begin suffocating rules after a number of rounds equal to their Constitution modifier (minimum 1). One Chuul focuses on the highest-armored target (the Fighter or Paladin) using Multiattack to grapple, while the second uses Tentacle Poison on any grappled creature. The Chuuls retreat into the deep water if reduced to fewer than 20 HP — they are not suicidal, they are lure-maddened and confused, not enraged. Ranged attacks from the Wizard and Rogue are at advantage when targeting a Chuul that has surfaced and is visible above water. The Fighter holding a narrow stepping-stone chokepoint forces one Chuul to approach through a 5-foot gap — a powerful defensive position that the party should be able to discover organically.
Terrain
Flooded grotto with stepping-stone paths (1-2 feet wide, requiring DC 10 Acrobatics to fight on without falling). Open water channels range from 3 feet shallow (difficult terrain, half speed) to 15 feet deep (swimming required, Athletics DC 12 each round). The rune-stone column is accessible via a single stone bridge 3 feet wide. Ceiling stalactites, 25 feet overhead, can be targeted with a ranged attack (AC 13) to drop a stalactite on a Chuul below for 2d10 piercing damage (DC 13 Dexterity saving throw for half). Darkness beyond torch range — creatures beyond 60 feet are heavily obscured.
Monsters
Tactics
The Resonance Warden activates as soon as any character approaches within 30 feet of the Obsidian Vault's wall. It does not start combat with a roar or leap — it simply turns to face the party and begins walking toward them at full speed, humming its distorted chord. The party has one round of free action before it reaches melee range, during which the Wizard may recognize the non-combat bypass option (DC 20 Arcana, or DC 18 if they have collected all six rune-fragments and succeeded at a DC 14 Arcana check on the seal). In melee, the Warden uses Multiattack every turn, targeting the highest-threat character (whoever dealt the most damage to it). At 40 HP or below, it triggers Discordant Burst — all creatures within 15 feet make a DC 14 Constitution saving throw or are stunned and deafened until end of their next turn. This is the most dangerous moment: if the Fighter and Paladin are both stunned, the Warden gets two free Slam attacks on the most vulnerable party member. Sonic Absorption means the Wizard should be warned away from thunder-damage spells. The Paladin's Divine Smite (radiant) is fully effective and the Warden has no resistance to it. The Rogue should position behind mushroom debris or obsidian shards for Sneak Attack opportunities on flanked rounds.
Terrain
The approach to the Obsidian Vault: a wide, flat cavern of bare black rock with no natural cover except scattered shards of obsidian (half cover, but razor-edged — moving prone through them deals 1d4 slashing damage). The Vault wall spans the entire far edge. The crack in the Vault glows faintly and pulses — any creature that ends its turn within 5 feet of the crack must succeed on a DC 13 Wisdom saving throw or be frightened of the Vault until the start of its next turn (the leaking Hollow Choir reaching out). The ceiling is low, 12 feet — no flying or levitation is possible at great height. Four obsidian stalagmites jut from the floor in a rough square, providing limited melee corridors and chokepoint opportunities for the Fighter.
The rubbing Mira made of the hidden cave map. Beyond its navigational use, a DC 16 Arcana check reveals that the cave biomes are arranged in a deliberate geometric pattern around the Vault — a containment array, not a natural formation. This is a major lore discovery.
A fist-sized crystal torn from the Resonance Warden's body after the fight. It hums faintly at the same frequency as the rune-stones. When held, the bearer can cast the Message cantrip at will, but only to creatures they can see. Additionally, once per day, the bearer may use an action to emit a pulse of harmonic energy — all creatures within 10 feet must succeed on a DC 13 Constitution saving throw or be deafened for 1 minute. Requires attunement.
A flattened oval of pale smoky quartz pulled from the Resonance Warden's chest cavity — its original command-key. A Wizard or Paladin who spends a short rest studying it and succeeds on a DC 14 Arcana check learns one word of the vault's pact language per day of study. Three words give them enough to attempt a full reinforcement of the seal without Mira's help — a possible route around her hidden knowledge.
A small obsidian vial found wedged into a crack in the vault's base, sealed with wax that crumbled at a touch. Inside is a thick black liquid that, when applied to a surface, carves the runes of a binding contract into it permanently. One use. The original pact-makers used this to write the first seal. Could be used to reinforce the Vault — or to write a new pact entirely.
Looted from a carved stone box near the Warden's last resting position — likely left as tribute by past generations of village elders. Contains 180 gp in mixed old and current coin, plus three uncut amethysts worth 50 gp each.
Story Hooks
The Dissolved Pact-Ink Vial and the Warden's Core Gem together point toward a future session where the party must decide: reinforce the old pact (perpetuating the soul-harvesting bargain Mira's ancestors made), write a new pact on their own terms (risky, unknown consequences), or attempt to destroy the Hollow Choir entirely — which may require entering the Vault. The Resonance Shard gives the party a persistent reminder of the Singing Path and a mechanical connection to the mystery going forward.
Conclusion
Wrap Up
The party defeats or bypasses the Resonance Warden and stands before the cracked seal. If they speak the six rune-fragments aloud in sequence — Voice, Hunger, Bound, Silence, Depths, Remember — the crack seals over with a sound like a single pure bell-tone, and the lure pulse goes quiet. Deep in Deepwick, the young phoenix stirs in its ash-bed, its feathers blazing back to full gold and white. It opens its eyes for the first time since the dream began, looks directly toward the cave network's depths, and then looks away. The party returns to Deepwick as something between heroes and bearers of terrible knowledge. Mira Stonehollow is waiting at the entrance. She reads the truth in their faces before they say a word. She closes her eyes, touches her obsidian pendant, and says quietly: "You found the crack. And now you know it isn't really a vault. It's a bargain." She does not elaborate. Not yet.
Cliffhanger
As the party settles in for a long rest, the young phoenix climbs from its ash-bed, walks to the center of the room, and begins to draw with one talon in the dust on the floor — the same six rune symbols, arranged not in a line, but in a circle. In the center of the circle, it scratches a seventh symbol that none of them have seen before. Then it looks up at the party, tilts its head, and waits, as if it knows exactly what it drew and is simply giving them time to catch up.
Next Session Hooks
- Mira Stonehollow must be confronted about the true nature of the pact — what did the underground villages give the Hollow Choir, and are they still giving it? Every death in the caves, every person who has ever died in the underground network, may have fed the Vault.
- The seventh rune the phoenix drew has no match in any fragment the party collected. It must come from inside the Vault itself — meaning someone, or something, communicated through the crack before it was resealed. The Hollow Choir may have sent a message.
- The Dissolved Pact-Ink Vial contains one use. Three factions in the underground network will soon learn the Vault cracked: the Deepwick elders who want to re-seal the old bargain, a group of younger cave-dwellers who want to destroy the Vault entirely, and an unknown third party whose recent tracks near the rune-stones suggest they were following the party the entire time.
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