BRIGHTMANTLE DISTRICT EISENHALL — OLDCITY SOURCEBOOK 1 THE DISTRICT THE DISTRICT BRIGHTMANTLE DISTRICT Research, Fabrication & the Forge of the City's Will Brightmantle District served as Eisenhall's engine of invention: the place where dwarven craft met divine authority, and where the city's most ambitious and dangerous projects were quietly pursued. Its cavern is wide and high-vaulted, the walls slotted with industrial pipe work and the ceilings strung with cable channels that once hummed with Tonal current. The party arrives here through the Earthdiving Bell excavated by the Eisenhall Mining Company on the surface — stepping out of the Bell and into a district that has been running on emergency power for a thousand years, dim but not dead. Cool blue light from Dugmaren's Diamond fills the cavern from the highest point, casting everything in long shadows and giving idle automata the look of watchful sentinels. Restoring Tharmekhûl's Bellows is the district's progression gate: once the Molten River flows again, the Mag-Lev corridor opens and the rest of ruined Eisenhall becomes reachable. Until that happens, Brightmantle is where the party will learn the rules of this place — what dwarven machines want, what they remember, and what the city's silence is hiding. GENERAL FEATURES Unless noted otherwise, all areas in Brightmantle District share the following properties. Architecture. The district is hewn from the Vuurcrown's igneous rock and dressed with cut stone facing. Corridor ceilings range from 14 to 20 feet in the working halls, rising to 40 feet in the Outflow Gallery. Surfaces are worn smooth near high-traffic routes and rough or shattered near collapse seams. Wall-mounted pipe housings and cable trays are standard features throughout. Doors. Interior doors are heavy iron-banded stone slabs on counterweighted pivots. Most can be forced open with a DC 18 Strength (Athletics) check. Tonal-locked doors require either the correct authorisation signal played into the nearest pipe socket or a DC 20 Dexterity check using thieves' tools. A door has AC 17, 27 Hit Points, and Immunity to Poison and Psychic damage. Illumination. Dugmaren's Diamond provides dim blue-white light throughout the entire district. It is enough to see by without difficulty — treat all areas as dimly lit unless stated otherwise. When Tharmekhûl's Bellows is reactivated, warmer amber light from the molten river supplements this glow in the lower corridors. Tonal Residue. The district's pipe network still carries faint Tonal current from Dugmaren's Diamond. Characters who press an ear to any pipe socket hear a low, steady hum — and occasionally a distant, fragmented chord that resolves into nothing. The Dao's Influence. The dao bound within the Great Tonal Machine exerts subtle pressure on any battery-powered information scroll in the district. Scrolls that have been altered by the dao present their information normally but include small directional nudges — emphasising certain passages, downplaying others — steering readers toward the Machine's core without alerting them to intelligence behind the text. DUGMAREN'S DIAMOND Power Source — Emergency Generator. A large arcane crystal mounted at the district's highest accessible point, pulsing with cool blue-white light. While the Bellows remain inactive it is the sole power supply for the entire district, feeding a wide range of systems at low intensity. While within Brightmantle District, all magic items with charges regain +1 additional charge every 8 hours. Additionally, spell scrolls have a 50% chance not to be expended on use. The Diamond cannot power the Bellows, the Mag-Lev line, or any full city-scale machinery. Those systems require the Bellows to be active. MOVEMENT & ACCESS Brightmantle traversal relies on three distinct systems, each with its own requirements and limitations in the district's current state. Earthdiving Bells. These are the party's primary means of arrival and inter-district transit. They are omni-directional vehicles that move through solid, unworked stone between fixed Ports. Each Bell requires an Earthdiver's Mace to engage the ignition console and navigate. Ports must be receiving active energy to accept a docking connection. Currently active Ports accessible from Brightmantle: Brightmantle Port (this district) and Marthammor's Gate (still accessible as a self-contained Tonal system, though the tunnel it serves is collapsed). Magmatic Levitation Trolley (Mag-Lev). Heat-powered trolleys that glide above the Molten River on thermal cushions. Currently dormant — the river channel is solidified and buried. Once Tharmekhûl's Bellows is reactivated, the blocked material melts down, the river is restored over a long rest, and the Mag-Lev line reactivates, linking Brightmantle to Vault Vergadain via the Outflow Gallery. On Foot. The district's internal corridors are navigable without special equipment. Wide industrial passages connect the Bell Station to the Laboratories, Infirmary, and the Bellows chamber. Some routes pass dormant Augur Automatons or sections of collapsed ceiling that count as difficult terrain. KEYED LOCATIONS The following locations are keyed to the Brightmantle District map. The district contains three mini-dungeons and the Port sub-levels. BRIGHTMANTLE PORT The Bell surfaces in a vaulted dock of dark stone, its walls lined with cable housings and iron mooring brackets. Several brackets stand empty; others still grip corroded chains. The cool blue light from somewhere high above catches the dust on everything and makes the room feel like the inside of a held breath. The Port is the district's entry point and the party's base of operations for Brightmantle. It consists of the Bell Dock itself, the attached Sub-Level garages, and the Wirecutter's Office. The dock is largely intact — the Eisenhall Mining Company's excavation disturbed only the last 30 feet of the Bell's access tunnel, and the BRIGHTMANTLE DISTRICT EISENHALL — OLDCITY SOURCEBOOK 2 THE DISTRICT THE DISTRICT Port's infrastructure survived the collapse in functional, if silent, condition. Bell Dock. A high-vaulted chamber with recessed mooring rings for up to four Earthdiving Bells. One ring is occupied by the party's Bell. The others are empty, though tool marks on the stone indicate Bells were present when the city fell. A Tonal socket on the north wall accepts instrument input to extend power to additional Ports; this currently does nothing, as the machine network is inactive. PORT SUB-LEVELS Accessible via a stairwell at the dock's far end, the sub-levels are a working industrial underbelly: wide-floored, low-featured, and built for machinery rather than people. The corridors smell of cold metal and old oil. Hangar Bays. Several large chambers served as garages and staging areas for the district's heavy machinery. Most contain the skeletal remains of Augur Automatons — massive drill-headed constructs built for excavation and maintenance. Without active Tonal signal they are dormant, but they are not damaged. A character who examines a dormant Augur and succeeds on a DC 14 Intelligence (Arcana) check determines that they would activate on the correct Tonal command, and that the command appears to have been a specific sung note in a specific key. Feature: Dormant Augur Automatons There are three Augurs in the hangar bays. If played the correct activation note (a deep sustained G-flat into the pipe socket near each bay entrance), an Augur wakes, performs its assigned excavation task, and returns to standby. The correct note can be found in the Wirecutter's routing logs. An Augur that receives a wrong note vibrates deeply and remains still. A second wrong note causes it to register as an intrusion response and attack until shut down by the correct note or reduced to 0 hit points. Use the Stone Golem stat block, replacing Slow with a Drill attack: +8 to hit, 2d10+5 piercing, and the target must succeed on a DC 16 Strength saving throw or be knocked Prone. Defunct Diving Bells. Two decommissioned Bells occupy the largest hangar bay, suspended in iron cradles. Both are inoperable — their Tonal cores were removed, likely for parts. A character who spends 10 minutes examining them and succeeds on a DC 13 Intelligence (Investigation) check finds a maintenance tag indicating the cores were transferred to the Laboratories of Laduguer , logged under Grey Ops allocation. The Wirecutter's Office. A cluttered room at the sub-level's heart, dominated by a central spool rack that still slowly generates wire from an automatic feed — enchanted to produce a continuous supply that the wirecutter would then measure, cut, and distribute. Over a thousand years, the unattended spool has produced an extraordinary accumulation of wire that has coiled, snarled, and spilled into the corridor outside. Treat the wire-choked corridor as difficult terrain for 30 feet in either direction. Feature: The Wirecutter's Logs A locked roll-top desk (DC 13 Dexterity, thieves' tools) holds the wirecutter's allocation ledger — a meticulous record of which wire grades ran to which machines and restricted zones. The ledger provides two pieces of significant information: 1. A routing map showing that a dedicated high-grade wire line runs directly into the Laboratories of Laduguer's sealed Grey Wing , allocated to 'Project Continuance — Eyes Only.' This is the access route to the Duerra Institute. 2. The Augur activation notes for each hangar bay, recorded in standard Tonal notation alongside maintenance schedules. Treasure: Wirecutter's Tools The desk also holds a set of masterwork wire-cutting and calibration tools worth 120 gp to any artificer or enchanter. A character proficient with artisan's tools who uses them gains advantage on checks to interface with or repair Tonal cable systems in Eisenhall. BRIGHTMANTLE DISTRICT EISENHALL — OLDCITY SOURCEBOOK 3 THE DISTRICT THE DISTRICT THARMEKHÛL'S BELLOWS Progression Gate — Vault Vergadain via Mag-Lev Forty stone pedestals fill the chamber in ordered banks, each one tethered by metallic cable to a fixed ocarina socketed into its base. Most pedestals stand fully raised — their surfaces dull and cold. A few glow faintly orange at their bases, as though something deep below them still remembers heat. At the far end of the room, a wall of fused grey stone seals what was once an outflow arch. Tharmekhûl's Bellows is the mechanical and spiritual heart of Brightmantle's power generation. Its forty ocarina-linked pedestals serve as remote indicators for the district's outflow chutes near the Molten River. When collapsed stone fills a chute, its pedestal rises to full height. As an ocarina's tones liquefy the blockage, the pedestal sinks, glowing orange, until it disappears into the floor — signalling free magma flow. The dwarves operated this system through coordinated tone patterns, mechanical airflow devices, and runic sequencing diagrams — allowing many chutes to clear simultaneously. Manually playing all forty ocarinas is impractical. The party must find the sequencing diagrams or devise their own method. The ocarinas cannot be removed from the room but function normally when played in place. Restoration Sequence. As pedestals descend, environmental heat increases, steam vents activate, and automated shutters begin cycling. Dormant maintenance constructs stir. When the majority of chutes are cleared, the sealed outflow wall begins to melt from within. After a long rest, the Molten River is fully restored, the Outflow Gallery is accessible, and the Mag-Lev corridor becomes operational. Feature: The Sequencing Diagrams The original runic sequencing diagrams for the ocarinas are posted on the chamber's eastern wall, partially obscured by mineral deposits. A character who spends 10 minutes clearing the deposits and succeeds on a DC 12 Intelligence (History) check can read them well enough to coordinate a full clearance in one hour with a group of four players each playing an ocarina. A Bard or character with musical proficiency who studies the diagrams for 10 minutes and succeeds on DC 10 Performance can instead run the clearance alone in two hours — the diagrams account for solo operation by a skilled musician. Feature: The Automaton Choir When Tharmekhûl's Bellows reaches maximum output and the Molten River flows freely, all Automaton Guardians in Brightmantle District that are still operational and now powered break into coordinated choral song. This is both extraordinary and deafening. The automated voices fill the entire cavern with a grand dwarven anthem composed to honour Tharmekhûl and Moradin. The sound travels through the pipe network into every connected chamber. Any character that hears the full choir and has a passive Insight of 12 or higher feels, unmistakeably, that this sound is doing something beyond celebration — as if the mountain itself is paying attention. (This is the Brightmantle condition for Moradinhall's entrance sequence, though the party has no way to know that yet.) Boss Encounter: The Lava Keeper. When the Molten River is restored and magma first enters the outflow channel, an elemental presence emerges: the Lava Keeper, a Greater Fire Elemental that has inhabited the sealed riverbed for centuries, treating it as its territory. It does not attack immediately — it reads the situation first. Encounter: The Lava Keeper What it wants: The Lava Keeper is not a guardian of the Bellows. It is a territorial elemental that settled into the sealed riverbed and regards the magma restoration as an intrusion into its space. Its instinct is to drive the party out — not to protect anything. Talking to it: A character who speaks Ignan or uses magic to communicate can attempt DC 15 Persuasion or DC 13 Nature check to explain that the magma channel is the river's natural state and the elemental is the intruder. On a success, the Keeper considers this for one round, then retreats into the river — and becomes a permanent, volatile feature of the Molten River corridor that the party will encounter again during Mag-Lev travel. Fighting it: If combat begins, use the Fire Elemental stat block (Monster Manual) with 178 hit points (20d10+60). Additionally, 1d4 Magma Mephits (Monster Manual) emerge from cracked floor tiles each round on initiative count 20 until the Keeper is defeated or placated. If the Keeper is destroyed: Its elemental essence dissipates and the corridor is clear. If it is persuaded to leave, it becomes a recurring hazard on the Mag-Lev route — a reason to not linger too long in transit. LABORATORIES OF LADUGUER Optional Mini-Dungeon — connects to Duerra Institute (hidden) The corridors here are wider than elsewhere in the district, built to move large equipment. Runic drafting tables stand fixed to the walls at intervals, their surface etched with half-completed diagrams. The air has a faint metallic taste. At the far end of the upper wing, a heavy iron door marked with Laduguer's sigil — a broken arrow — is sealed tight. The Laboratories served as Brightmantle's principal research and development complex: responsible for large-scale magical fabrication, industrial enchantment, and all sanctioned and unsanctioned Grey Ops initiatives. Its upper wings are devoted to device-testing, runic refinement, and prototype storage — many still partially functional and hazardous. The facility's deepest wing contains the Grey Vaults: sealed chambers housing projects that the ruling clans officially discontinued. The Vaults are accessible either through the wire routing corridor discovered in the Wirecutter's Office, or via the alternative entrance in Dumathoin's Depths UPPER RESEARCH WINGS Concept Forges. Semi-circular chambers with stone-topped work surfaces and wall-mounted socket panels. Enchanted items left on surfaces here when the city fell are still faintly active. Roll 1d6 when players examine a Concept Forge: on 1-2, one item on the surface activates unexpectedly (DM's discretion — a spark, a sound, a brief illusion). On 3-5, the surfaces are inert but contain useful components (worth 50 gp in arcane materials). On 6, a Prototype Device is intact and usable. BRIGHTMANTLE DISTRICT EISENHALL — OLDCITY SOURCEBOOK 4 THE DISTRICT THE DISTRICT Treasure: Prototype Devices (d4) 1. Resonance Fork: Struck against a Tonal socket, reveals the last command signal the socket received. 1 use. 2. Pipe-Reader: Applied to a pipe, allows the user to hear current Tonal traffic within that pipe run for 1 minute. 3. Augur Key: A Tonal key pre-loaded with the standard Augur activation sequence. Works on any Augur that hasn't been individually recoded. 4. Stoneshaper's Band: A metal ring that, once per day, allows the wearer to cast mold earth at will for 1 hour. Runic Drafting Rooms. Two rooms contain in-progress runic work from before the collapse. A character with Arcana proficiency who spends 30 minutes studying the diagrams and succeeds on a DC 14 Intelligence (Arcana) check learns the specific runic notation used for Tonal authorisation in this district — granting advantage on future checks to operate Brightmantle's Tonal systems. THE GREY VAULTS The deepest wing requires the wire routing access discovered in the sub-levels, or the Duerra Institute alternate entrance. The Vaults are prefaced by a corridor of sealed iron doors, each marked with a project designation in old dwarven script. Most are empty — projects discontinued and cleared before the collapse. Two are not. Grey Vault I: The Azerwrought Project What it was: A tripartite transmutation system designed to convert dwarven flesh into living metal, cage the soul within an arcane matrix, and cast a fully formed Azerwrought body from prepared alloys. Three chambers in sequence: (1) Subject intake — restraint frame still present, deeply scored by something that struggled. (2) Alloy feedstock — mostly emptied, but traces of exotic metals remain. (3) Crucible-automaton assembly — heavily damaged, but the crucible itself is still sealed. What happened here: During the collapse, dwarves with clearance used the system to attempt escape from death by forcibly entering the project. When alloy supplies ran out, the operators fed stone into the matrix. The first Stone Cursed emerged from these attempts — their petrification permanently binding mind and soul into mineral form, their touch converting others. First-generation Stone Cursed still move through these chambers. They are not hostile by design — they are attempting to help, converting dying creatures in an anguished misunderstanding of mercy. Second-generation Stone Cursed created by these encounters only petrify for 24 hours. The sealed crucible: One complete Azerwrought body remains inside the jammed crucible machine, fully formed, conscious, and immobile. It has been aware — alone — for a thousand years. It does not know how long it has been there. It communicates via vibration through the machine's hull. Grey Vault II: Project Beauty What it was: A dedicated vault housing a beholder captured by Eisenhall's researchers to explore dream-state reality shaping. The beholder was kept in a reinforced metal cube compressed between two heavy pistons, with enchantments allowing controlled sensory input and targeted spellcasting into the interior. The research team fed it dream-infusion teas and oneiromantic scripts. What happened: Over centuries of total isolation, the beholder progressed into a Death Tyrant form within the cube. It is mentally active and physically confined. The vault is saturated with dream-residue — a faint unreality clings to everything in the room. The cube: The piston housing is intact and the beholder cannot exit. However, it can communicate through the sensory ports — and it has had a very long time to perfect what it wants to say. Dream research: The vault's shelves contain oneiromantic research documents and dream-infusion apparatus. A character who studies these materials for a long rest and succeeds DC 15 Arcana gains the ability to cast Dreamstride once before their next long rest. The Death Tyrant is aware of anyone who handles the research and will attempt to begin a conversation. Hidden: Entrance to the Duerra Institute Behind a false wall in the Azerwrought chamber (Investigation DC 19), a narrow service passage leads via the wire routing corridor to the Duerra Institute — the sub-dungeon where the dao-binding project was developed. This is also accessible from Dumathoin's Depths . The passage is marked, in very small script near the hinge, with the words: Project Continuance. Eyes Only. BRIGHTMANTLE DISTRICT EISENHALL — OLDCITY SOURCEBOOK 5 THE DISTRICT THE DISTRICT LOWER TRUESILVER INFIRMARY Progression Gate — Berronar's Burrows The reception is cold and very quiet. Rows of empty chairs face a stone admissions desk; a thin crust of mineral deposit has formed across the desk's surface. The halls beyond branch into wards that smell of old stone and something underneath it — not decay exactly, but the memory of distress, thick and stale in the air. The light from somewhere deeper in the building flickers irregularly. The Lower Infirmary held the city's quarantine zones, operating theatres, medical testing, and its sanitorium. Its primary function, however, was archival: patient records, long-term study logs, and case histories were housed here in secure stacks, making it the most frequently visited building in Brightmantle for anyone needing access to medical history — or to information that needed to not be in the Laboratories. The Lower Infirmary also provides the gate into Berronar's Burrows , the city's residential district — via the Upper Infirmary above. That path is currently blocked by the Nothic's barricade at the upper stairwell. MEMORIAL STELES & THE SECRET ARCHIVE Innocuous stone steles are placed at dead ends throughout the Infirmary's hallways, each dedicated to Infirmary staff who completed two centuries of service. There are several steles spanning 1,200 years of dedications — from Hemor-Y400 to Hemor-Y1600. Investigation: The Impossible Name A character who examines more than one stele and succeeds on DC 15 Intelligence (History) notices that a single name appears on every stele — each built 50 years apart across twelve centuries. A dwarf lifespan is 3-4 centuries. The name is impossible. This name on each stele is a braille-pattern button. Pressing it opens a hidden door in the corresponding stele's wall, revealing a Grey Ops medical archive — records of which projects used the Infirmary and why, cross-referencing the Laboratories' classified work. The secret door in the reception stele is the most significant (Investigation DC 20). It leads to the main Grey Ops archive, containing the full list of active and discontinued projects at the time of the collapse. THE NOTHIC The Lower Infirmary is inhabited. A creature has been living here for longer than the city has been dead — a Nothic, though it was not always one. It arrived before the collapse: a Meazel from the Shadowfell, drawn to Eisenhall in the disguise of a dwarf, relishing the coming catastrophe. The Infirmary staff placed it in sanitorium isolation for its open use of Shadow Magic. The collapse came. The Meazel remained. A thousand years of solitude, fed on a diet of the Infirmary's concentrated tragedy, transformed it into a Nothic. It is deeply lonely. It is also incapable of tolerating company — every attempt it has made at contact has ended in violence, because it no longer understands how to not be terrifying. It spends most of its time in the wards, cutting tragedy from the walls with enchanted surgical tools and animating what it cuts as either Simulacra of itself as it once was (Meazel stat block, acting out old memories) or as Shadows (Monster Manual) when the grief is too much to hold. Encounter: The Nothic (formerly a Meazel) Use the Nothic stat block (Monster Manual). The Nothic has additionally retained its Shadowfell nature: it can cast darkness at will and has Resistance to necrotic damage. Roleplaying it: The Nothic's Weird Insight reads the deepest regret of whoever it looks at — and it leads with this, immediately, every time. Not as a threat. It simply doesn't know any other way to start a conversation. It then asks if they've come to let it out. What it wants: To leave. It cannot leave without help — the barricade it built to keep itself in (as much as to keep others out) has trapped it too. It will not ask for this directly. It will circle the subject repeatedly. The enchanted surgical tools: Three sets remain on its person. Each can cut the emotional residue from a location and animate it. In the Nothic's hands they produce Shadows or Meazel Simulacra. In a player's hands they could theoretically be used elsewhere in the dungeon for creative purposes — or sold for 300 gp each to the right buyer. THE BARRICADE The Nothic has spent centuries dragging medical machinery to the upper stairwell door, creating a barricade of several tonnes of stone-and-iron hospital equipment. The door to the Upper Infirmary — and the route to Berronar's Burrows — is behind it. Obstacle: The Barricade The barricade cannot be shifted by force alone in any reasonable timeframe. It requires one of the following approaches: 1. Negotiate with the Nothic. If the party convinces the Nothic to help move the barricade — or to accept that they will not harm it — it will dismantle its own work in about an hour, moving each piece back with meticulous care. 2. Find the Infirmary's maintenance automata. The Lower Infirmary had two heavy-lift maintenance constructs. They are disabled in a storage ward (Investigation DC 13 to find them). Reactivating them requires a Tonal command note (DC 15 Performance or Arcana to determine the note, or a Resonance Fork from the Labs). Once active, they can clear the barricade in 20 minutes. 3. Use an Augur Automaton. If the party has reactivated an Augur from the sub-level hangars and can direct it here, its drill can dismantle the barricade in one round — and likely damage the door as well. Treasure: Medical Stores The Nothic has no interest in medicine. The wards, operating theatres, and storage rooms are largely untouched, their supplies degraded by time but not looted. Characters who spend 30 minutes searching find: 2d4 Potions of Healing , 1d4 Potions of Greater Healing , a sealed case of Antitoxin (6 vials), and a Healer's Kit with 20 uses. Additionally, a character with Medicine proficiency who succeeds on DC 14 Medicine can identify and salvage one Potion of Remove Curse from the quarantine ward's pharmacological stores. CONNECTIONS FROM BRIGHTMANTLE Destination How to Access Berronar's Burrows Through the Lower Infirmary (Upper stairwell), once the barricad Vault Vergadain Mag-Lev Trolley via Outflow Gallery, once Tharmekhûl's Bellow BRIGHTMANTLE DISTRICT EISENHALL — OLDCITY SOURCEBOOK 6 THE DISTRICT THE DISTRICT Marthammor's Gate Earthdiving Bell (Port already active, but tunnel is collapsed) Dumathoin's Depths Through the Duerra Institute (via Labs or Depths entrance) Duerra Institute Grey Vault passage in the Labs, or Dumathoin's Depths entrance BRIGHTMANTLE RANDOM ENCOUNTERS Every hour of game time spent in Brightmantle District, roll a d20. On a result of 17 or higher, a random encounter occurs. Roll 1d10 on the table below. d10 Encounter 1 1d3 Stone Cursed (MM) wander from the direction of the Laboratories, arms outstretched, attempting to 'help.' 2 A Magma Mephit (MM) has crawled up a warm pipe. It is confused and angry. 3 1d4 animated Concept Forge prototypes (use Flying Sword stat block) pursuing a residual activation loop. 4 A Simulacrum animated by the Nothic — a shadow-Meazel acting out a memory from before the collapse. It does not attack unless cornered. 5 A section of wire-snarl from the sub-levels has animated. Use Animated Object (Rope) but with 40 ft. reach. 6 1d2 Shadows (MM) detached from a grief-saturated ward. 7 A dormant Augur Automaton activates on an old maintenance loop. It excavates a random wall section until shut down or destroyed. 8 Faint Tonal music from the pipe network. The dao is testing signal range. All battery-powered scrolls read by the party in the next hour have been subtly edited. 9 A pocket of cold air from a quasi-elemental rift — 10 ft. radius of extreme cold. DC 12 Con or 1d6 cold damage and Disadvantage on Dex checks for 1 minute. 10 A Nothic Simulacrum of the original Meazel stands motionless in a corridor, weeping. It is harmless. It was not given instructions.