Put this dungeon wherever you need it to be, but in my game it'll be hidden away in the Golden Lands, requiring an expedition of significant distance from civilization. This is one of those dungeons where your weapons aren't much use for anything, and I don't explain the true nature or origin of the place.
Charged Walls: The walls in this dungeon are dull copper, audibly humming and releasing the occasional visible spark. Anyone touching the walls, or being connected through conductive material, takes d6 damage, ignoring armour, continuing for each turn of contact. The floors and ceiling are white stone, which does not conduct the charge, but give off a faint glow. The natural caves in the eastern half of the dungeon are not affected.
A: A natural cave entrance high on a steep cliff face. Leads into an extremely tight tunnel that requires crawling to navigate.
B: A collapsed well shaft that drops straight into 1.
Wandering Encounters: Roll d6 whenever the group move to a new area, loiter, or make a lot of noise. On a 1 they encounter something, on a 2 they get a clue that something is nearby.
1: Magnetic Surge: A sudden magnetic force pulls metal towards Room 15 for a moment.
2: Static Crash: Deafening static noise effectively deafens the group for the next d10 minutes. They group cannot communicate by talking for this time.
3: Gravity Distortion: Roll d20 and multiply by 10. Gravity functions as this percentage of normal for the next d10 minutes.
4: d6 Charge Imps: STR 8, DEX 14, WIL 5, 2hp, Shock (d6, ignore armour). Driven by curiosity. Immune to physical attacks. Electricity causes damage as normal.
5: d4 Charge Men: STR 10, DEX 12, WIL 10, 5hp, Shock (d8, ignore armour) Driven by desire to keep people out of the dungeon. Immune to physical attacks. Electricity causes damage as normal.
6: Charge Hulk: STR 16, DEX 5, WIL 10, 14hp, Shock (d10, ignore armour) Driven by desire to be left alone.
Charge Beings: These creatures all similar in nature. They are immune to physical attacks, but electricity or other energy-based attacks cause damage as normal and eventually causes them to disperse in a flash. They resemble humanoids composed out of pulsing blue light, flowing plasma, with flashes of lightning sparking from their body. If they leave the dungeon or the connected caves their form collapses entirely. They are sapient and speak in a buzzing language that you do not understand. They are not innately hostile, but are impatient and easily frustrated.
Spark Keys are copper rods with a square cross-section. They give a harmless spark when pushed against a target, but their intended purpose is to deliver a small charge to various doors or chests, which unlocks them. Any device requiring a Spark Key to activate will have a square hole clear to see, where the key should be pushed. After a successful use the Spark Key is depleted. Any electrical spark will serve the same purpose if no spark keys are available.
Immediate room contents are listed. Contents in parentheses require further investigation to discover.
1: Well Bottom
Floor: Pile of Rubble (rocks, 15s in coins, a mirror, a Spark Key)
East: Stone Carving in Wall (monstrous lion, can be pushed to open up to 2)
South: Boarded over door to stairway down (easily broken through)
2: Hanging Owls
Ceiling: Hanging Lanterns (stylized owls, conduct charge)
Floor: Scraps of paper (scrawled notes in a foreign language)
East: Door to corridor.
West: Carved Stone Wall (angelic beings fighting a monstrous lion, can be pushed open to 1)
3: The Garden
Floor: Glowing Stream (acts as normal water)
Wall: Patches of bright green moss (conduct charge from the walls, smell and taste minty and delicious)
Ceiling: Wooden carving (simply drawn scene of a ship sailing under stars)
South: Stone Doors to 4.
North: Stone Doors to corridor.
4: Skeleton Pile
Floor: A heap of skeletons (human, completely bare of clothes or possessions, chalk diagram drawn on floor underneath resembling an electric circuit)
West: Ornately Framed Mirror (slightly rippling, touching with a spark key causes it to part and allow access to the corridor)
North: Stone Door to 3.
East: Stone Doors to 5.
5: Fully Copper Room
Floor and Ceiling: Copper (shocks for d6 damage ignoring armour, as the walls)
East: Stone Doors to 6.
West: Stone Doors to 4.
6: Ancestor Chamber
Walls: Carved images (people lined up to enter a sphere, emerging as angelic beings)
West: Stone Doors to 5.
East: Mirror (slightly rippling, touching with a spark key causes it to part and allow access to 7)
7: Hands of Death
Floor: Copper Box (opened with a Spark Key, contains a pair of white metal gloves (Hands of Death: Clap hands to cause a random living thing in your sight to take a WIL Save or fall into a death-like sleep. Clapping again awakens them without harm.)
Floor: Stone Box (opened with a Spark Key, contains protective gloves that prevent shock from touching the walls)
West: Door to 6.
8: Dead Man
Floor: Skeleton (tattered clothes, old-fashioned sword, 30s in old currency, tattered rope, one Spark Key)
West: Door to Corridor
South: Cobwebs (conceals a crack barely able to be squeezed through, leads to tunnels)
9: Coil Spikes
Floor: Sunken and Covered in Spikes (metal, 6 inches long, conduct charge from the walls, cause an additional d8 damage if fallen onto, a spark key has been dropped amongst the spikes)
North: Door to stairway up.
West: Door to stairway down to 10.
10: Failed Lion
Floor: Pile of scrap metal (parts of a copper lion-like sculpture, very intricate, parts worth 10g to an engineer, one spark key hidden amongst the scrap)
North: Door to stairway up to 9.
West: Door to stairway down.
11: Spark Chest
Floor: Copper Chest (opened with a spark key, contains four porcelain lion figurines worth 1g each)
East: Door to Corridor.
12: Copper Doors
North: Copper Double Doors (charged as the walls, magnetically sealed and opened by a Spark Key, to 15)
South: Copper Double Doors (charged as the walls, magnetically sealed and opened by a Spark Key, to corridor)
East: Door to 14.
West: Door to 13.
13: Black Switch
West: Black Ceramic Switch (pulling disables the glow from the floor and ceilings, reversible, if the switch in 14 is also pulled then Charge Beings cease to exist and any powered devices are disabled)
East: Door to 12.
North: Scratched patch of copper wall (not charged, can be opened quite easily leading to a stone tunnel)
14: White Switch
East: White Ceramic Switch (pulling disables the charge from the walls, reversible, if the switch in 13 is also pulled then Charge Beings cease to exist and any powered devices are disabled)
West: Door to 12.
15: Matter Converter
Large Copper Sphere (hollow, can be entered through rear, closing the door activates the machine causing d12 damage each turn to the being inside. Upon death they are converted into a Charge Man, retaining their free will, but being unable to leave the dungeon. The machine can be stopped opening the door from the outside, but a discharge causes d6 damage to all in the room, ignoring armour).
South: Double Doors into 12.
16: Oil Bath
Floor: Copper Bathing Pool (filled with black oil, warm, restores physical damage in a matter of minutes, Spark Key at bottom)
North: Stone Door to Stairway Up.
17: Hope Destroyer
Huge Metal Machine (Trumpet-like funnel, slowly humming, will answer any question with the answer most likely to cause the group to lose hope and turn back, can be broken up for parts worth 10g to an engineer)
East: Tunnel maze.
18: Waxy Cave
Walls and Ceiling: Waxy Stone (slippery, smells like paraffin)
Floor: Tiny craters filled with liquid (dripping from ceiling, oily, burns well as fuel, the largest has a Spark Key discarded at the bottom)
North-West: Tunnel to 19.
North-East: Tunnel to 20.
19: The Prison
North-East Corner: Iron Prison Bars (contains a colossal skull, looks reptilian, single eye-socket, 25s of coins thrown in over floor).
South: Tunnel to 18.
West: Pile of collapsed ceiling rubble (concealing a stone door to a corridor).
Walls: Root-like Tendrils (Move slowly, grasp upon contact, easily cut away)
South West: Tunnel to 18.
South East: Tunnel maze.
North: Tunnel to 21.
21: Force Eater
North: Huge bulb-like plant (STR 10, DEX 1, WIL 1, 4hp, growing out of wall, starts to open upon sensing warmth, can repeat phrases it has heard before [Help! What is that thing? Get inside. I'm not paid enough for this. Various foreign-language phrases], anyone nearing the thing is drawn in by a strange pulling force, requiring a STR Save to avoid being swallowed up. Swallowed beings lose d6 STR each turn until cut out. Once it has swallowed something, it exerts a pushing force impairing all physical attacks against it)
Walls: Root-like Tendrils (Move slowly, grasp upon contact, easily cut away)
South: Tunnel to 20.