The Drowned Vaults of Malachar
The Drowned Vaults of Malachar
The party descends into a flooded subterranean vault built by the long-dead archmage Malachar, whose soul was reportedly sealed within its deepest chamber. A rival cult — the Tideworn, devoted to an aboleth patron — has already breached the outer gates and is racing to unseal Malachar's soul-prison, hoping to bind his power to their dark god. The adventurers must navigate rising waters, ancient traps, and the cult's fanatics before the final seal is broken and something far worse than a dead wizard is unleashed.
Read Aloud
You stand at the threshold of a colossal iron gate, its hinges blown inward with tremendous force, seawater still weeping through cracks in the surrounding stonework. The stench of brine and something older — like parchment soaked in ocean and left to rot — coils into your lungs with every breath. Torchlight catches the edges of crude fish-sigils chiseled freshly into the ancient stone arch above you, overlapping the original runes with violent contempt. At your feet, the floor is slick with a centimeter of black water that mirrors the darkness ahead, and somewhere deep below, you hear the rhythmic groan of stone grinding against stone, as if the vault itself is breathing.
Description
The party arrives at the breached entrance to the Drowned Vaults. The original rune-sealed gate has been blown open from the outside — the Tideworn cult used some kind of explosive alchemical charge, evidenced by scorch streaks radiating outward from the lock housing. Three dead cult initiates in salt-bleached robes lie near the entrance, killed by a pressure-trap that fired stone spikes from the walls — the bodies are still pinned to the opposite wall. A shallow river of seawater flows steadily inward along the floor, fed by cracks in the ceiling that weep brine. The cult has been here for perhaps six hours.
DM Notes
DC 12 Intelligence (Investigation) to examine the gate and determine the cult used alchemical charges, not a spell — suggesting they lack a high-level arcane caster. DC 14 Wisdom (Perception) to notice fresh wet bootprints leading deeper in — at least eight sets. DC 15 Intelligence (Arcana) to identify the original gate runes as Malacharian Binding Script, a rare arcane tradition used to seal soul-vessels. The spike trap has already fired and is spent. Use this scene to establish the cult as reckless and numerous, and to hint at Malachar's soul-seal lore.
Read Aloud
You push through a warped wooden door into a vast chamber where rows of stone shelving — once laden with tomes — have collapsed into the knee-deep water that floods the floor. Sodden pages drift past your legs like pale dead fish, their ink bloomed into purple clouds. Phosphorescent lichen clings to the vaulted ceiling twenty feet above, casting a cold, sickly blue light over everything. A large stone reading desk at the chamber's center remains above the waterline, and atop it someone has very recently spread a rough map — weighted down with a dagger — marked with a route to a location labeled in the Old Tongue: The Cradle of the Sealed Voice.
Description
The old scriptorium is half-flooded. Most of Malachar's written records are ruined, but this is where the party finds the cult's abandoned field map — a crucial intelligence asset. The map shows the layout of the next three vault levels, with the cult's route marked and two chambers circled with the note drown the wards. A surviving waterproof scroll case wedged in a collapsed shelf contains one of Malachar's personal research notes describing the soul-seal: it requires three Resonance Keys (tuning-fork-like relics) to be shattered simultaneously in the final chamber. The cult has retrieved two of the three keys. The third is somewhere the cult has not yet reached.
DM Notes
DC 13 Intelligence (Investigation) to find the cult's map on the reading desk — no roll needed to see it, but the roll reveals the annotation about drowning the wards. DC 16 Intelligence (Arcana) or DC 14 Intelligence (History) to translate the Old Tongue on the map and understand what the Cradle of the Sealed Voice is. DC 15 Wisdom (Perception) to notice a waterproof scroll case jammed under a collapsed shelf — contains Malachar's research notes. The Cleric automatically recognizes the soul-seal description as a form of divine binding that would be catastrophically unstable if broken by an outside force rather than the original caster. This is a pure roleplay and exploration scene — reward curiosity heavily.
Read Aloud
The corridor ahead is a throat of black stone, barely eight feet wide, with water rising to your waists as you wade forward. The ceiling is low and close, dripping steadily, and your breath sounds very loud. Ahead, around a blind bend, you catch the orange flicker of a hooded lantern — and then it goes dark. The water around your legs suddenly stirs, pushed by bodies moving fast and deliberately through the black, and a harsh whispering voice hisses from the darkness ahead: This is sacred water. Leave your bones here.
Description
A Tideworn ambush team of cult fanatics has been left behind to slow pursuers. They fight in the flooded corridor deliberately, using the water and darkness to their advantage. The cult members wear waterproofed dark leather armor and fight with javelins and shortswords. Their leader, Subcantor Vael (use Spy stat block, leading 3 Bugbears reskinned as cult enforcers in waterlogged hide), has extinguished their lantern and is attempting to use Stealth to coordinate a flanking assault. This is the party's first direct contact with the Tideworn. Vael will attempt to flee deeper into the vault if reduced below 10 HP, potentially becoming an interrogation target.
DM Notes
DC 15 Wisdom (Perception) to avoid being surprised — the water movement is the tell. The corridor is 8 feet wide and 40 feet long with a 90-degree bend in the middle: Fireball cannot be used without endangering the party in the tight space. The waist-deep water counts as difficult terrain for Medium and Small creatures — cult enforcers have already adapted and suffer no penalty (DM ruling: they move at full speed, representing their preparation). Counterspell is useful if Vael uses a poison vial as a thrown item, which the DM can frame as a spell-like ritual action. If Vael is captured alive, he knows the cult's general plan and the location of the third Resonance Key but will require a DC 15 Charisma (Intimidation) or DC 17 Charisma (Persuasion) check to get him to talk. Water eliminates any ranged advantage — remind the Rogue that Sneak Attack still applies if an ally is adjacent to a target.
Read Aloud
The passage opens into a hexagonal chamber where the water falls away entirely — the floor here is elevated, a dry island of worked stone carved with concentric rings of runes that hum at a frequency you feel in your back teeth rather than hear. At the chamber's center, mounted on a basalt plinth, a slender silver fork the length of a forearm vibrates with a faint, continuous tone. The walls around the chamber are lined with iron cages bolted into the stone, and inside each cage the bones of a long-dead figure slump — wearing the academic robes of Malachar's original order, every one of them missing its skull.
Description
This is the resting place of the third Resonance Key — a tuning-fork relic that is part of the soul-seal mechanism. The cage-bound skeletons are Malachar's former apprentices, interred here as guardians by a ward that animates them if the Key is touched without first solving the ward puzzle. The puzzle is a sequence of rune-rings on the floor that must be walked in the correct order (outer to inner, then inner to outer again) — the correct sequence is encoded on Malachar's research notes from the Scriptorium. If the party has the scroll, they can solve it without combat. If not, disturbing the Key triggers the guardian encounter. The cult has not yet reached this room — their route circled around it, either missing it or unable to solve the ward.
DM Notes
If the party has Malachar's research notes from Scene 2, a DC 13 Intelligence (Arcana) check deciphers the rune sequence and allows safe retrieval of the Key — no combat. Without the notes: DC 20 Intelligence (Arcana) to deduce the sequence from the runes alone — on a failure, the guardian skeletons animate (see Encounter 2). The Key itself resonates painfully when held near living flesh — whoever carries it takes 1 point of thunder damage per minute, a subtle detail that rewards Perception (DC 12) and hints at the Key's soul-binding nature. The Fighter with Adamantine Armor might offer to carry it since their armor is magical and thus the Key vibrates differently in their grip — a nice DM reward for that magic item. Emphasize the missing skulls on every skeleton — an unanswered detail that implies Malachar did something worse than killing his apprentices.
Read Aloud
The final chamber is immense — a cathedral of black stone that plunges downward in a perfectly circular shaft, the walls carved with thousands of screaming faces all oriented toward the center. You stand on a wide stone balcony that rings the shaft, and fifty feet below, a platform of pale marble juts out over absolute darkness. On that platform, seven figures in bleached robes chant in unison, their voices resonating up the shaft like a pipe organ tuned to grief. At the platform's center, two silver forks have already been placed in stone slots — and the chanting cult leader, her arms raised, is calling for the third.
Description
The climactic chamber. The party has the advantage of the high balcony overlooking the ritual platform below. The Tideworn High Cantor Seraveth and six cult fanatics are in the middle of the unsealing ritual. They have two of the three Resonance Keys already slotted. The party holds the third — meaning the ritual cannot complete without them, which gives them leverage and a moment of dramatic choice before combat. Seraveth will attempt to negotiate or threaten, then fight. The shaft below the platform is 200 feet deep and filled with dark water at the bottom — falling from the platform is potentially lethal. The ritual platform connects to the balcony by two narrow stone bridges.
DM Notes
Give the party a full round of free actions before initiative to act on the environmental advantage. The Wizard's Fireball is ideal here — the platform is open and 50 feet below, removing corridor restriction. The Cleric's Spirit Guardians will dominate the narrow bridges and force cult members to take the long route. Seraveth is immune to Banishment because she is a native Material Plane creature (human), consistent with the Key Spells rule for Banishment. If the party throws the third Key into the shaft, the ritual fails permanently — but Malachar's soul (now destabilized) escapes the seal partially and manifests as a voice that echoes up the shaft, setting up a future plot hook. If Seraveth is captured, she can explain the aboleth patron who sent the cult — another future thread. The six cult fanatics prioritize rushing the bridges to reach the Key-holder.
Monsters
Tactics
Vael extinguishes his lantern as the party rounds the bend, plunging the corridor into darkness (disadvantage on attack rolls for creatures without darkvision). Vael uses Cunning Action to Hide in the waist-deep water on his first turn, then coordinates the three enforcers to charge the front-liners while he targets the back row (Wizard, Cleric) with his hand crossbow from concealment. Enforcers use Surprise Attack on any creature that did not succeed on the Perception check. If Vael drops below 10 HP, he calls a retreat and attempts to Disengage and flee around the next bend — he is a potential prisoner. Enforcers fight to the death (fanaticism), but without Vael's direction they become reckless and lose tactical coordination.
Terrain
Flooded corridor, 8 feet wide, 40 feet long with a 90-degree bend in the middle. Waist-deep (3 feet) black seawater throughout — counts as difficult terrain for all creatures (Medium and smaller) except the Tideworn Enforcers, who have adapted and move at full speed. No line of sight beyond the bend. Ceiling is 7 feet high — no flying. No space for Fireball without catching the party in the blast. Two iron sconces on the walls are unlit. Total darkness without party light sources.
Monsters
Tactics
The five Guardian Shells activate simultaneously the moment the Key is disturbed without the correct ward sequence. They do not pursue beyond the chamber's threshold — they are bound to guard the Key, not destroy the trespassers. Two immediately move to flank the Key-holder (their sole priority target). The other three form a perimeter around the plinth to prevent the Key from being replaced and the ward re-engaged. They cannot be reasoned with. They are constructs — immune to Spirit Guardians' radiant damage (constructs are not affected by Turn Undead, but Spirit Guardians still deals damage — note that the Antimagic Susceptibility trait means any shell within an antimagic field is incapacitated). The Wizard can use the Ring of Spell Storing's stored spell (if charged) to cast from safety. This encounter is SKIPPED entirely if the party solved the rune-ring puzzle.
Terrain
Dry hexagonal chamber, elevated 4 feet above the flooded corridors. The concentric rune-rings on the floor create difficult terrain if a creature moves through them in the wrong sequence (DM discretion — use to reward tactical positioning). The iron cages lining the walls can be torn open (DC 15 Strength check) and used as improvised difficult terrain obstacles. The basalt plinth at center is 3 feet tall and 2 feet wide — the Key sits atop it and can be grabbed as an object interaction. 30-foot ceiling with hanging iron chains — the Rogue can use these for high-ground positioning with a DC 12 Athletics check.
Monsters
Tactics
Seraveth begins with Spiritual Weapon already active (bonus action, established before the party arrives). On her first turn she casts a 3rd-level Thunderwave directed up the balcony stairwell if melee characters descend — DC 15 Con save or 8d8 thunder and pushed 10 feet back onto the bridge (potentially off). She uses Bane on the second turn targeting the Fighter, Rogue, and Cleric. She concentrates on Control Water, which she uses to cause the water in flooded upper corridors to surge, threatening to flood the lower platform (dramatic pressure — give the party 3 rounds before water reaches ankle depth on the platform). Counterspell will be the Wizard's most critical decision: Seraveth casts Hold Person on the Fighter on round 2 (level 3 spell — meaningful Counterspell decision). Six Tideworn Fanatics split into two groups of three: one group defends the slotted Keys, the other rushes the bridges to reach the third Key held by the party. Fanatics are willing to grapple the Key-holder and drag them over the edge — DC 13 Strength saving throw or be grappled. If four or more Fanatics drop, the remaining ones break morale and leap into the shaft (suicide rather than capture — disturbing detail). Seraveth uses Legendary Resistance if hit by Banishment (she is a Material Plane native, so Banishment would send her to a demiplane — she would resist this). Spirit Guardians on the narrow bridges is extremely effective: alert DM — give Fanatics a ranged alternative (they carry light crossbows) to prevent the spell from trivializing bridge defense.
Terrain
Circular shaft, 80 feet in diameter, open in the center with a 200-foot drop to black water below. The party begins on the upper stone balcony (50 feet above the ritual platform). Two narrow stone bridges (5 feet wide, 30 feet long) connect balcony to ritual platform — single file movement only. The ritual platform is pale marble, 40 feet in diameter, with two Resonance Keys already slotted in stone fixtures at center. Two large iron braziers on the platform provide orange light (can be knocked over as an action — creates a 10-foot fire hazard zone). The balcony has a low parapet (half cover). The shaft walls are carved with screaming faces — in the second round of combat, Malachar's Voice manifests from the walls and whispers one useful tactical warning to the party (DM choice: e.g., she fears the third key more than your blades — destroy it and the ritual dies).
A slender silver tuning fork, 18 inches long, engraved with Malacharian Binding Script. It hums continuously at a frequency only barely audible. If all three Keys are assembled (not shattered), a DC 17 Intelligence (Arcana) check over a short rest reveals they can be used to re-seal Malachar's vault — or theoretically to seal any soul into a prepared vessel. Worth 500 gp to the right scholar. Possible quest item for a future session.
A driftwood-and-iron staff. Functions as a +1 Quarterstaff. Once per day, the wielder can cast Thunderwave at 2nd level (DC 14) without expending a spell slot. The staff smells faintly of deep ocean even in dry air. Attunement required.
A waterproofed scroll recovered from Seraveth or Vael containing the cult's internal codes and the name of their aboleth patron: Ul-Sharak of the Forgetting Deep. Also contains the location of the cult's surface base of operations — a warehouse in the harbor district of the nearest city.
Found on the ritual platform — contributions from cult members funding the expedition. Contains 340 gp, 12 pp, and three carnelian gemstones worth 50 gp each.
A waterproof iron-clasped folio found in a hidden compartment beneath the ritual platform, revealed when the sealing mechanism partially activates. Contains three complete spell formulae: Malachar's Memory Extraction (a unique ritual), notes toward a 9th-level spell that has no name yet, and a personal letter addressed to no one describing what he sealed inside his soul alongside his consciousness — the memory of how to unmake a sleeping god. This is a major lore item.
Story Hooks
The Tideworn Cipher Scroll points directly to the cult's surface headquarters and their aboleth patron Ul-Sharak, setting up a future investigation arc in the city harbor. Malachar's Research Folio establishes that the archmage's soul contains a memory the aboleth is specifically hunting — the party now holds the folio, making them a direct target. The assembled Resonance Keys could be used to re-seal the vault or to create a new soul-vessel, raising uncomfortable moral questions about Malachar's fate and potential resurrection.
Conclusion
Wrap Up
With Seraveth defeated and the third Resonance Key kept from the ritual slots, the unsealing fails. The two Keys already placed in the stone fixtures crack and go dark as the ritual's energy collapses — but not silently. A shockwave of displaced soul-energy rolls through the vault, and for thirty seconds every carved screaming face on the shaft walls opens its mouth and exhales a single, synchronized breath of icy air. The vault then goes still. Water begins to recede slowly through cracks in the floor. The party can retrieve Malachar's Research Folio from beneath the platform, search Seraveth and any surviving prisoners, and take stock of what they have prevented — and what they have stumbled into. If Vael was taken prisoner, he answers questions sullenly but completely once Seraveth is confirmed dead, his loyalty severing cleanly with her fall.
Cliffhanger
As the party climbs back toward the surface, lantern light ahead — the vault entrance is no longer dark. Three figures in harbor-city constable uniforms stand at the shattered gate, and behind them, barely visible in the pre-dawn light, a carriage with no livery and curtained windows. One of the constables calls out to the party by name. Not by class. Not by reputation. By their actual names. And from inside the curtained carriage, in a voice that is somehow wet and vast and entirely too close, something says: They did well. Bring them to me.
Next Session Hooks
- The Tideworn Cipher Scroll leads the party into the harbor district to locate the cult's surface base, where they discover it is far larger and more organized than a splinter group should be. Ul-Sharak has been operating for decades.
- Malachar's Research Folio contains a letter from the archmage himself, addressed to whoever holds this folio, warning them that the memory sealed in his soul cannot be allowed to surface — and offering cryptic instructions for finding the one person alive who knows how to destroy a memory without destroying the soul that holds it.
- The constables and the carriage represent a third faction who has been watching the vault — possibly a secret government intelligence body, possibly something else entirely. Their knowledge of the party's names and their connection to whatever is in that carriage is the immediate dangling thread demanding resolution.
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