Campaign: The Cleansing of Steamfort

Location: Steamfort, The Rusted Deep (Subterranean Dwarven Metropolis) Level Range: 5 to 9

Campaign Overview & Themes

"The Cleansing of Steamfort" is a grueling, atmospheric plunge into a quarantined dwarven metropolis that has fallen not to a traditional army, but to an insidious, bio-magical ecological disaster of its own making. Centuries ago, the dwarven alchemists of Steamfort engineered a blue-green mycelium to consume their industrial waste. This event, The First Spawning, birthed Mycelia-Zul, The World-Root, and its planetary immune system: the goblins.

Now, the geothermal vents of Steamfort are clogged with this very same blue-green growth. The trapped toxic gases and pervasive spores have plunged the quarantined dwarven populace into hallucinogenic paranoia. The players, armed with Lady Elara of Kigum’s ancestral map, must infiltrate the sealed city, navigate a nightmare of rusted metal and creeping blue flora, reactivate the Great Bellows, and confront the tragic, corrupted leadership of the dwarves.

Core Themes:

Industrial Decay vs. Rampant Nature: The juxtaposition of jagged, rusted dwarven machinery violently overgrown by beautiful, bioluminescent blue fungi.
Claustrophobia and Paranoia: The air is thick with hallucinogenic spores. Allies turn on each other, and the environment plays tricks on the mind.
The Price of Hubris: The realization that the existential threat to the continent was manufactured in the very forges the players are trying to save.

The Spore Infection Tracking System (DM Mechanic): Throughout the campaign, players accumulate "Spore Points" from inhaling the blue fog, taking damage from Spore-Cougher Swarms, or using the Azure-Lace Symbiote armor.

Tier 1 (1-3 Points): Mild euphoria. The character gains 30ft Telepathy with other infected creatures.
Tier 2 (4-6 Points): Deepening connection. Disadvantage on all Wisdom saving throws. Can hear the whispers of the goblin hive-mind.
Tier 3 (7-9 Points): Mycelial integration. Physical blue veins appear on the skin. The character gains resistance to poison and psychic damage but must make a DC 15 Wisdom save to attack any goblinoid or fungal creature.
Tier 4 (10 Points): Total Assimilation. The player loses autonomy to Mycelia-Zul, becoming an NPC pacified by the World-Root.

The Sandbox / Regional Guide

Steamfort is a vertical, subterranean sandbox divided into distinct tiers of descent.

The Quarantine Gates (Surface Access): A colossal adamantine bulkhead sealed from the inside. The surrounding rock is stained blue. Without Lady Elara's map, the players must navigate the lethal, unmapped exhaust shafts to bypass this gate.
The Copper Slums (Upper Tier): Once the residential district for the working class, now a haunting maze of rusted hovels. Thick blue fog pools around the ankles. It is patrolled by paranoid, hallucinating dwarven citizens who view outsiders as "metal-eating demons."
The Overgrown Forges (Middle Tier): The industrial heart of the city. Blast furnaces are choked with enormous, fire-resistant fungal blooms. The automated assembly lines have been compromised, creating terrifying flora-machine hybrids.
The Deep Archives (Hidden Sector): A sealed, hermetic vault containing the alchemical logs of The First Spawning. Heavily guarded by the goblin hive-mind's assassins, who seek to destroy the evidence.
The Lung of the Mountain (Bottom Tier): A cavernous chamber housing the Great Bellows—titanic, geothermal-powered fans designed to vent the city. It is currently flooded with a concentrated, liquid-like spore mist and serves as the throne room for the corrupted Forge-Master.

Factions & Reputations

1. The Iron Paranoiacs The majority of surviving dwarves, trapped in the city and driven mad by the hallucinogenic spores. They are loyal to High Forge-Master Thordin and believe the blue fungus is a blessing from the earth, while viewing non-infected beings as horrifying monsters. Interaction: Hostile, but can be pacified via non-lethal subdual or by curing the localized air supply.

2. The Hive-Mind Vanguard Forces of Mycelia-Zul that have infiltrated the city via the deep root network. Composed of feral Spore-Cougher Swarms and elite Mycelial Stalkers. They do not care about the dwarves; their sole mission is to ensure the Great Bellows remain broken so the spores can reach critical mass and assimilate the city. Interaction: Always hostile.

3. The Sober Holdouts A desperate, starving band of dwarven engineers hiding in an airtight vault in the Copper Slums. Led by Chief Vent-Warden Helga, they wear crude rebreathers and are desperately trying to repair localized air filters. Interaction: Suspicious but helpful. If players earn their trust, Helga provides schematics to the Overgrown Forges.

The Villains & Lieutenants

High Forge-Master Thordin (The Tragic Puppet) Once a brilliant and compassionate leader, Thordin sealed the gates to prevent the "plague" from reaching Kigum. Tragically, he trapped himself in the epicenter. His mind is now completely compromised by the spores. He views the World-Root not as a threat, but as the ultimate, peaceful culmination of dwarven engineering. He wields a massive, spore-venting gravity hammer.

Kragx, The Azure Stalker (The Network's Blade) A terrifying, teleporting goblinoid assassin sent by Grob-Tuk the Ancient. Kragx travels instantly through the fungal root network. He stalks the players throughout the campaign, striking when they are vulnerable (especially during puzzles) to ensure the map to the ventilation controls is destroyed.

Timeline of Doom

If the players long rest too frequently or ignore the main objective, the hive-mind’s assimilation accelerates:

Day 1: The blue fog rises to the Copper Slums. Vision is reduced to 15 feet; Spore Infection saves are required every hour.
Day 3: The flora-machine hybrids breach the Sober Holdouts' vault. Helga and her engineers are assimilated.
Day 5: High Forge-Master Thordin completely dismantles the Great Bellows to build a massive Spawning Pool. The Cleansing becomes impossible, and Steamfort is permanently lost to the Viridian Cradle.

The 5-Act Structure

Act I: The Exhaust Breach

Using Lady Elara’s map, the players must repel down the treacherous, geothermal exhaust shafts. They encounter the sheer scale of the fungal infestation as they fight off initial Spore-Cougher Swarms. The act concludes with a claustrophobic skill challenge to slip through the crushing, rusted gears of the ventilation fans before dropping into the Copper Slums.

Act II: City of Hallucinations

The party navigates the Copper Slums, experiencing the hallucinogenic paranoia firsthand. They must decide whether to slaughter the maddened, innocent dwarves or expend resources to bypass them. They discover the Sober Holdouts and must help them secure their vault against an incoming wave of infected Iron Paranoiacs to secure the keys to the Overgrown Forges.

Act III: The Overgrown Forges

The party descends into the industrial dungeon. This act is heavily puzzle-oriented. They must re-route magma flows and solve complex pressure-valve puzzles to un-clog the geothermal vents. The hive-mind pushes back fiercely, animating the very assembly lines to unleash Flora-Machine Hybrids upon the party.

Act IV: The Sins of the Fathers

Before they can reach the Bellows, Kragx the Azure Stalker ambushes the party in the Deep Archives. In the aftermath of this brutal, high-mobility fight, the players discover the ancient logs of The First Spawning. The horrific truth is revealed: the goblins are a dwarven mistake, and Mycelia-Zul was born in these very rooms.

Act V: The Cleansing

The players breach The Lung of the Mountain. They confront High Forge-Master Thordin in a multi-stage boss battle. They must fight Thordin while simultaneously interacting with the colossal machinery to re-engage the Great Bellows. Upon success, massive hurricane-force winds of pure, super-heated air flush the lower levels, curing the surviving dwarves but revealing the massive root-tunnels leading down to the Viridian Cradle—setting the stage for the campaign's finale.

Dungeons & Set Pieces

Dungeon: The Overgrown Forges

A sprawling, multi-level industrial complex where rusted catwalks are suspended over lakes of glowing blue, spore-infested magma.

Enemies: Clockwork Wardens choked by vines, Spore-Cougher Swarms bursting from old iron pipes, and Mycelial Stalkers striking from the shadows.
Mechanic - The Flora-Machine Hybrids: Dwarven automatons that have been re-wired by the intelligent mycelium. When they die, they explode into a cloud of Spore Points unless killed with fire or cold damage.

Set Piece 1: The Pressure-Valve Puzzle

To unlock the blast doors to the lower levels, players must balance the pressure of three massive steam-boilers.

The Catch: The dials are covered in hallucinogenic moss. The player reading the dial must make a Wisdom save; on a failure, they perceive the numbers backward or see the pressure dropping when it is actually overloading. The party must communicate and manage valves across three different combat platforms while fending off waves of infected dwarves.

Set Piece 2: The Bellows Chamber (Boss Arena)

A gargantuan circular room dominated by four titanic fan blades in the floor.

Hazards: As the fight progresses and players activate the fans, sections of the floor become high-velocity wind tunnels. Stepping on an active fan launches characters 40 feet into the air.
Thordin’s Tactics: Thordin uses his gravity hammer to slam players into the fan blades or knock them into the toxic exhaust vents on the perimeter. The players must lock in four master control rods to activate the final purge sequence while surviving his assault.

Evolving Loot & Vestiges

1. The Azure-Lace Symbiote (Acquired from Fizig in Act I) A living armor made of severed blue mycelium.

Base: +1 Light Armor. Grants advantage on Stealth checks in subterranean environments.
Evolution (Tier 2 Infection): The armor links to the user's nervous system. As a reaction to taking damage, the armor hardens into bark-like plating, granting resistance to the triggering damage type. However, using this ability grants the user 1 Spore Point.
Evolution (Tier 3 Infection): The armor sprouts tendrils. Grants a climbing speed equal to walking speed and the ability to cast Spider Climb at will. Removing the armor at this stage deals 4d10 necrotic damage.

2. The Bellows-Key of Thordin (Looted from the Forge-Master) A massive dwarven warhammer that doubles as a master control wrench for the city's machinery.

Weapon: +2 Warhammer. Deals an extra 1d8 fire damage.
Ability - "The Lung's Roar": Once per long rest, the wielder can slam the hammer into the ground, casting Gust of Wind (Save DC 16). In addition to the spell's normal effects, any toxic gas, magical fog, or spore clouds in the area are immediately dispersed.

3. Respirator of the Sober (Gifted by Chief Vent-Warden Helga) A beautifully crafted, brass-and-leather rebreather.

Effect: The wearer is completely immune to airborne poisons, toxic gases, and the accumulation of Spore Points via inhalation.
Limitation: The respirator's alchemical filters degrade. It requires a fresh vial of distilled water and charcoal to function each day, making resource management a priority in the deep dark.