Caves of Corrosion

LEVEL 1: ADMINISTRATION LEVEL

A-1) Entrance Tunnel:

The entrance to Biggarswith Hollow stands half-sunken in a hillside of jagged rock, its weather-worn timbers stained a sickly green. The faint tang of metal hangs heavy in the air, and a metallic, acrid bite stings your nostrils with every breath. Rusted mining carts lie overturned like forgotten toys, their wheels coated in a thin, iridescent film. A low groaning creak echoes from deep within the mine, and a faint distant drip of water rings out steadily.

A-2) Foremans Office: This cramped office is in disarray, with a split desk spilling papers soaked in greenish fluid. A torn mining map hangs on the wall, its features unreadable and claw-like gouges scar the doorframe leading out.

• Feature: A scrawled entry in a ledger mentions "strange tremors, worse than before" just before the entries stop abruptly.

A-3) Mess Hall: Broken tables and chairs lie in splintered heaps amid shattered mugs and bowls. A wall tapestry hangs in tatters, half-melted by acid, while faint blood trails lead toward the opposite doorway.

A-4) Storage Room: Shattered crates and collapsed shelves spill corroded tools and ruined supplies across the floor. Green-black sludge seeps through cracks in the stone, and a metal-bound strongbox, tarnished green, is half-fused to the wall.

• Strongbox Loot: The strongbox is covered in corrosive acid. A player which attempts to unlock it takes 1d6 acid damage. DC 15 Thieves' Tools contains 25 gold pieces, 4 gemstones (worth 50g each), and 2 potions of healing.

A-5) Medical Bay: Rust-covered cots line the walls, their linens dissolved into brittle tatters. Glass vials on a broken shelf are coated in a thin, greenish crust, and the faint coppery scent of old blood hangs in the air.

• Note: The medical bay is not well stocked or complete. Mostly designed for isolation of sick miners, bandaging cuts and slinging broken limbs.
• Feature: DC 13 investigation - Half-buried in the dirt lies a jagged fragment of shell, the size of a man’s forearm. Its surface is ridged and ochre-colored, dulled with scratches but still unnervingly hard to the touch. Along the edges, the chitin has splintered into razor-sharp points, and faint seams of soft pink tissue cling to the underside, shriveled and dried like old sinew. Even separated from the creature that shed it, the piece feels unsettlingly alive.

A-6) Barracks: Rows of simple bunks line the walls, most reduced to warped frames and shredded bedding. Several dead bodies lie scattered across the room, their faces twisted in pain, with burns and holes in their flesh. The stench of copper and rot hangs heavy in the air.

• Feature: A player with a passive perception of 14 or greater will notice a faint movement from one of the bodies — a subtle twitch of a hand or a weak groan. If the players approach, they will see that this dwarf is still alive, though barely. Otherwise a player who succeeds on a DC 14 Perception/Investigation check will notice the same thing.
• The players may make a DC 13 Medicine check to recognize that Thorin is severely injured, suffering from acid burns on his face, particularly around his eyes. They also realize that while his wounds are not immediately fatal, he will die without assistance. Stabilizing him requires magical healing or a successful DC 10 Medicine check using a healer’s kit or improvised materials.

Thorin Silverhammer: Thorin is a middle-aged dwarf with a stocky frame and a once-proud beard now singed and patchy from the acid. His eyes are crusted over with corroded flesh, and his face is marred with scar tissue from burns. His leather mining attire is tattered and corroded in places, especially around his shoulders and arms.

• Personality: Thorin is hardy and stubborn but also deeply shaken by the events. His voice trembles as he speaks, not out of fear but from the sheer pain of his injuries. He’s slow to trust the party initially, but if the players show kindness or patience, he will open up.
• Motivation: Thorin wants to know if the other miners are alive. He is desperate to hear good news but will react with sorrow if the party tells him otherwise. His ultimate goal is survival — he just wants to get out alive.

Information

• Thorin does not recall many specific details of the incident, only that he heard an ear piercing screech followed by a loud crash. As he turned to look in the direction of the noise, he felt a searing pain in his face and the world went black as he fell unconcious.
• The foreman of the mine had been growing concerned about something, though he did not know what. He was exchanging correspondence with a foreman from a nearby mine then he ventured into the mines on his own the day before the attack.
• Later that day, these large, chittering bug-like creatures began coming from some lower parts of the mine. They collapsed several side tunnels on the minin level to cut off their movements and blocked off the tunnel leading below the mining level.
• It wasnt his call, but the foreman was in the lower levels when they collapsed the tunnels.

Development! - As the players exit the barracks, read:

• As you step out from the barracks, the dim chamber beyond is no longer empty. Five shapes linger near the base of the lift — pale, sinewed forms half-crouched like waiting predators. Their limbs are long and jointed wrong, ending in hooked claws that scrape faintly against the stone. Plates of dull chitin shift across their bodies with each subtle movement, and a low, rhythmic clicking echoes through the chamber as their heads turn toward you in unison.
• Combat
• 5x Chorvix Drone (Tithonoloth Denmother Drone mini)
• 1x Chorvix Skiver (Tithonoloth Scythe Drone mini)
• Roll initiative for the Skiver, but do not place them on the battlemap yet. After two rounds of combat, the Skiver will emerge from the lift and join the fight.

A-7) Supply Lift: Description: A winch-operated platform elevator descends to the next level. The wood is scorched in places, and the chains are tarnished with a greenish patina.

• Feature: The crank on the winch is damaged and will need to be replaced before the lift can be operated. Players may salvage the wreckage to repair the winch with a successful DC 13 Investigation check.
• Failing to salvage an appropriate crank will require the players to climb down the supply lift. They may make a DC 14 Athletics check to climb down the cable, on a fail the player falls 30ft and takes 3d6 bludgenoning damage.
• The crank at the bottom is still intact and can be cranked to activate the mineshaft.

Mining Level

M-1) Supply Station: Broken crates and rusted tools lie scattered across the floor, and the faint smell of rot mingles with the sharp tang of acid. A warped shelf tilts dangerously, its contents spilled onto the ground below.

• Loot: 2 intact Pitons and 50ft of usable rope - DC 14 Investigation reveals a hidden compartment beneath a barrel which contains 1x potion of acid resistance and 1x potion of fire resistance as well as 1x scroll of Tidal Wave

M-2) Formans Office: A small chamber with a scorched desk sits at its center, its surface warped and covered in scattered notes. Broken shelves line the walls, their contents spilled and rotting on the floor.

• Feature: If the players search the desk they will find the foremans notes scattered about. Give them the handouts from the "Scattered Notes" section.

M-3) Collapsed Corridor: As you step into the corridor, the sound of chittering echoes from multiple sources. Ahead, a 30-foot-wide gap spans the tunnel where the floor has collapsed. On the far side, a steep, rubble-covered slope offers a possible way out. Below, in the darkness, chitinous creatures skitter across the debris, their mandibles clicking in an eerie rhythm. The only intact path across is a rusted mining rail, stretching precariously over the gap, creaking under its own weight.

In order for the players to get through this corridor, they must either climb 30ft down to the collapsed portion below and fight their way across, or attempt to cross the mining rails which spand the distance of the corridor.

Enemies: (Loot Studios)

• 2x Chorvix Drone - (Tithonoloth Denmother Drone mini)
• 3x Chorvix Sciver - (Tithonoloth Scythe Drone mini)
• 1x Chorvix Burrower - (Tithonoloth Tunneller Drone mini)
• x Chorvix Ravager - (Tithonoloth Soldier Drone mini) - not immediately present

The drones, burrower and ravager below will seem oblivious to the party, but if a player touches the ground in the pit below, they will immediately attack.

After 2 rounds of combat, roll initiative for the 3 Skivers and add them to the battle.

Skill Challenge

• DC 15 Athletics or Acrobatics check to attempt to cross the rails. Failing a check will result in the player falling 30ft to the pit below and taking 2d6 bludgeoning damage.
• Roughly halfway across, the rail will give way slightly. The player nearest to the center must succeed on a DC 14 Athletics saving throw, or fall 30ft to the pit below and take 2d6 bludgeoning damage.
• If any player falls into the pit below, the creatures will attack.

M-4) Storge Chamber: Moldy sacks and toppled barrels fill this cramped room, with a thick, sour smell clinging to the air. The walls are streaked with greenish-black stains that trail down from the ceiling.

M-5) Miners Workshop: Heavy workbenches line the room, stained with dark marks and etched with deep gouges. The air reeks of metal and vinegar, and broken hammers and chisels lie scattered across the stone floor.

• Loot: an intricate looking beard bead that has a strange mental weight to it(see Bead of Enduring) can be found beside an Artisans Kit.

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Trap! - While moving through the corridor between M-5 and M-6

• As the players walk through the narrow corridor, when one of the players reaches the Y junction of the mine cart track, green acid erupts from the ground. Any creature within 20ft must make a DC 15 dexterity saving throw, taking 3d6 acid damage of a fail or half as much on a success.
• DC 13 investigation - Preliminary checks will determin that a tunnel created by one of the bug creatures had a pool of acid inside that was then covered by the nearby tunnel collopse. The players movement disturbed the earth surrounding it which caused the pressure from the gasses to erupt outward.

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M-6) Miner's Bunkroom: Ragged bedrolls and dented footlockers are scattered across the floor. The air smells of damp cloth and acid, and faint scratches mark the floor near the back wall.

Hidden Loot: DC 13 Investigation - A pair of silver rings in a hidden compartment beneath the lid of one foot locker.

• One mundaine worth 25gp
• One Ring of Spell Storing - 1x Cure Wounds, 1x Bless, 1x Guiding Bolt

M-7) MINERS' MESS HALL: Splintered wooden tables and broken chairs are strewn across the room. A large iron pot, now a melted, twisted heap, sits in the center of a stone firepit.

Note: If the players did not fight the enemies in the corridore, they will encounter them in here. If you have lots of time, you could include them here anyway.

• Loot: A healing salve (acts as a Potion of Healing) can be found in a storage cupboard (Investigation DC 13).

M-8) Collapsed Chamber: The ground here is broken and uneven, the jagged edges of stone supports circling a wide, dark pit that drops into a vast chamber below, sporadically illuminated with a faint, green glow. A soft bubbling sound echoes from within, and the sharp, stinging acrid smell grows stronger.

Players will need to descend the 60ft drop in order to get to the next level. They can do this by:

• Utilizing any physical or magical resources at their disposal.
• A player with darkvision would be able to faintly make out a large pool of water, directly below the opening.

The pool of water below the opening is partially acidic, as a corrosive reaction spreads through it, slowly converting the water into a bubbling, toxic sludge.

• A creature who enters the pool will recieve 1d6 acid damage upon entering it, as well as for every 10ft they swim in it.

Final Chamber: The cavern expands before you, a vast chamber of jagged rock formations jutting from the uneven ground. Small acidic streams carve winding paths between them, their faint hiss echoing in the air. Scattered pools of bubbling green sludge glow faintly, their surfaces rippling with each drip from above. On the far side of the chamber, a massive black stalactite looms, its surface slick with rivulets of acid. Beneath it, a grotesque form swells out of the stone itself—an enormous pod of chitin and soft, pulsing flesh. From its upper half rises a monstrous insectoid shape, its limbs ending in long, scythe-like blades that twitch restlessly in the dark, ringed by clusters of glistening egg sacs. The creatures head raises toward you and as it notices you, lets out a loud, shrill shriek. A brief moment later, the ground begins to rumble softly and several other bug like creatures emerge from the ground.

This cavern is now home to the Chorvix Broodmother. Her shriek called several Chorvix to her defence and they immediately attack the party:

Enemies

• 2x Chorvix Skivers
• 1x Chorvix Brood tender
• 1x Chorvix Burrower
• 1x Chorvix Broodmother

Development!

• If the players did not kill the Chorvix in the Collapsed Corridor, after 3 rounds of combat, a Chorvix Ravager erupts from the wall and enters the encounter.

The Cave-In

When the Broodmother dies, the Chorvix hive-mind fractures. The surviving creatures across the mine — drones, burrowers, and skivers — begin digging erratically in panic, collapsing their own tunnels and chewing through load-bearing rock.

Within minutes, the once-stable network of passages becomes a deathtrap of shifting stone, acidic runoff, and echoing, directionless screams.

The players will need to navigate 3 escape challenges. Utilizing spells, equipment and abilities should be rewarded with success and/or easier DCs.

Read:

The Broodmother lets out a shriek that rattles the marrow in your bones — a keening wail that rises, warps, then fractures into silence. Her vast body convulses, thrashing against the walls until the air fills with the crack of snapping limbs and the hiss of boiling acid.

For a long heartbeat, there is silence. Then, faintly, you hear the sound of chittering — where once it was calm and rhythmic, now it comes fast and broken, sharp with panic. The walls shudder as shapes dart within them — Chorvix fleeing in blind terror, weaving through the walls like burrowing fish through silt.

The tremors grow stronger. Dust rains from the ceiling, followed by chunks of rock that shatter across the floor. Cracks split through the chamber as the hive tears itself apart around you.

Escape Challenge 1

Climbing Out of the Broodmother’s Chamber

The only way out of the chamber is to scale the 40-foot wall leading up to the next level.

Climbing

The climb is resolved in rounds.

• With a successful DC 14 Strength (Athletics) check, a character climbs 10 feet.
• On a failed check, the climber can make a DC 14 Dexterity saving throw to maintain position.
• On a failure, they fall 5 feet.

The shaft is unstable, and collapses worsen as the Chorvix burrow frantically through the walls.

Collapse Checks

At the end of each round, the DM rolls 1d20 + 3 vs DC 13.

• On a failure, a collapse event occurs — roll 1d4 on the Collapse Check Table below.
• After three total collapse checks, the tunnel gives way entirely.
• Any creature not yet out is buried in the collapse and will require assistance to be freed.
• Any rescuer who stays behind to dig out another creature begins the next escape challenge with disadvantage on their first check due to exhaustion and falling debris.

Collapse Check Table

Escape Challenge 2

Goal:
Escape the collapsing mining tunnels and reach the Administration Level before the structure gives way.

How It Works

• At the start of each round, roll 1d6 to determine which skill or save applies (see table below).
• Each player rolls once using the indicated skill.
• Add all successful rolls together into a Cumulative Total.
• The party must reach a Cumulative DC of 14 × the number of players before they reach 3 failures.
• Example: For a 5-player party, the total target is 70 (14 × 5).

Each success represents coordinated progress — navigating hazards, keeping formation, and guiding one another through chaos.
Each failure represents delays, wrong turns, or injuries, increasing the pressure as the mine deteriorates.

Skill Table

All rolls use a base DC of 14 unless a hazard (collapse, acid steam, etc.) temporarily increases it.

Outcomes

• Success (Cumulative Total Reached before 3 Failures):
  The group breaks through a half-collapsed service door and scrambles into the Administration Level as the mining tunnels collapse behind them.
• Failure (3 Failures before Reaching Total):
  The mine caves in behind the party, forcing them through a rough detour. They reach the next level winded and burned, each member taking 1d6 acid or bludgeoning damage (DM’s choice) and gaining 1 level of exhaustion.

Escape Challenge 3

The party has reached the Administration Level , which is surprisingly still relatively the same as it was when they players arrived. The exit is in sight, but the players will need to make one final leap to escape.

You run through the administration level, the walls and ground rumbling around you. Sunlight of the exit gleams ahead through the fractured doorway. The roar of the collapsing mine fades behind you—until a deep, groaning crack splits the floor.

The ground begins to fall away, chunks of stone and broken timber tumbling into the darkness below. You run, the floor crumbling beneath your feet, and just as the last stretch gives way as you make one final leap.

Each player must succeed on a DC 13 Athletics or Acrobatics check. If a player fails, they fall into the collapse.

A player who succeed may use their reaction make a DC 13 Athletics check to to catch the falling player.

If a player falls into the collapse, they die as they fall deep into the network of caves and are buried under the mine.