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The Sunken Foundry

The Sunken Foundry

The Sunken Foundry (Level 15)

Overview

An ancient, pre-cataclysm clockwork manufacturing facility that sank to the bottom of the ocean centuries ago. Despite being submerged, the facility's localized Aether-wards have kept the interior entirely dry, though the immense pressure of the ocean groans against the reinforced glass bulkheads. The Foundry's automated defenses—massive clockwork constructs and lethal assembly lines—are still fully active, mindlessly producing weapons for a war that ended ages ago.

Environmental Hazards & Gimmicks

  • Localized Gravity Inversions: The ancient wards are failing. Certain rooms have perfectly spherical gravity (pulling towards the center), while others have inverted gravity. Crossing the thresholds between these zones forces immediate orientation checks to avoid falling.
  • Automated Assembly Lines: The dungeon is a factory. Conveyor belts move at high speeds, massive automated hammers stamp down rhythmically, and robotic arms attempt to "weld" or "bolt" players if they are caught on the line.
  • Pressure Breaches: The glass bulkheads look out into the deep ocean. Stray attacks (like a missed Fireball or heavy bludgeoning damage) can crack the glass. A cracked bulkhead creates a massive jet of high-pressure water (treat as a Geyser that knocks players prone). If shattered completely, the room floods in 1 round, subjecting everyone to crushing deep-sea pressure.

Key Locations/Rooms

1. The Sub-Bay Docking Ring

  • Description: The party enters via submarine or magical diving gear into a large, circular moon-pool chamber.
  • Sensory: The air is stale, dry, and smells heavily of ozone and machine oil. The distant thud of heavy machinery echoes through the metal walls.
  • Mechanic: The airlock door is sealed with a heavy mechanical puzzle requiring players to manipulate gears to match a specific rhythmic timing.
  • Encounter: 2 Clockwork Dragons (Use Young Bronze Dragon stats, change breath weapon to a cone of superheated steam) activate from dormant alcoves when the puzzle is touched.

2. The Stamping Press

  • Description: A massive, 200-foot long corridor. The entire floor is a conveyor belt moving toward the far door. Above, four gigantic, 20-by-20-foot metal pistons slam down onto the belt in a rhythmic sequence.
  • Mechanic/Trap: Players must navigate the conveyor belt.
    • The belt moves them 20 feet forward at the end of their turn.
    • The pistons slam down on initiative count 20, 15, 10, and 5.
    • Getting caught under a piston deals 10d10 bludgeoning damage and restrains the player until the piston lifts on the next round. Players must time their dashes perfectly.

3. The Zero-G Assembly Sphere

  • Description: A massive spherical room, 100 feet in diameter. There is no gravity here. Floating in the center is a half-completed, massive clockwork engine.
  • Mechanic: Combat in 3D. Players must push off the walls or the floating engine parts to move. Weapons with recoil push the user backward.
  • Monsters: A swarm of Modron welders (use Flying Sword stats, but dealing fire/welding damage) swarm the players, perceiving them as rogue organic matter interfering with the assembly.

4. The Quality Control Furnace

  • Description: A room dominated by a massive, blindingly bright Aether-furnace. The heat is so intense it warps the air.
  • Sensory: The sound of roaring flames. Metal glows cherry-red.
  • Mechanic: Just being in the room deals 1d6 fire damage per round. The party must cross a narrow, retractable bridge over the furnace to reach the control panel.
  • Trap: The bridge retracts if weight exceeds 300 lbs. The players must cross one by one, or use magic. If someone falls in, they take 12d6 fire damage.

5. The Master Overseer (Boss Encounter)

  • Description: A vast control room overlooking the ocean floor through a massive dome of reinforced glass. In the center of the room is the Master Overseer, a colossal, multi-armed clockwork construct wired directly into the facility's mainframe.
  • The Boss: The Master Overseer (Use an Iron Golem stat block with legendary actions and lair actions).
  • Boss Mechanics:
    • The Assembly Arms: Four massive mechanical arms drop from the ceiling. On initiative count 20, they target random squares, attempting to grapple and lift players into the air, dropping them the next round.
    • Electrified Floor: The Overseer can use a lair action to electrify the metal floor grid. Players must jump onto non-conductive crates or take 4d8 lightning damage.
    • The Glass Dome: The ultimate hazard. The Overseer's heavy attacks can damage the dome. If the Overseer is defeated by a massive explosive attack, or if it intentionally targets the glass in a final act of spite, the dome shatters. The players have 1 round to hit the emergency blast door button before the crushing ocean pressure instantly kills anyone left in the room.
  • Loot: The Core of the Overseer (A legendary power source that can power an airship or city block) and a set of Clockwork Armor (Plate armor, AC 18, grants advantage on Strength checks but disadvantage on Stealth).