Brinefathom Caves @brinefathomcaves - Tumblr Blog

Welcome to Brinefathom Caves

The pirate haven of the Whistling Isle is honeycombed with sea caves that make eerie sounds when the wind blows over the island. Legend has it that, two centuries ago, the fiendish pirate Barnabas Brimstone buried a massive treasure here before being dragged back down to hell. But that's not the only legend tied to the brinefathom caves.

They say that the caves are so deep they pierce the underworld. They say that strange creatures, driven underground when the island was settled, still survive down there. They say that the restless spirits of people who died there are doomed to sail a lightless sea. But mostly, they say that Brimstone's gold is far from the only treasure waiting in the depths.

Brinefathom Caves is a dungeon24 project (as Sean McCoy's dungeon23, but in 2024) where I try to make a megadungeon over the course of the year by keying a room (almost) every day.

2024 is over and the dungeon is finished, so now I'm working on editing this monster!

#brinefathom caves #introduction #dungeon23 #dungeon24 #megadungeon #dungeons and dragons #listen up me hearties

Brinefathom Caves 2025 Year-End Update

Welp! I didn't get nearly as much done this year as I would've liked to, largely just because of mid-year procrastination. Then when I finally got my drive back in the waning months of the year, I had other creative responsibilities that limited my ability to catch up. I admit, I was also disheartened by the release of 5.5e, which I still haven't read in any detail.

I'm currently about halfway through updating the rooms for level 3. Level 2 is mostly done--I just need to write more about the various cults and add some more treasure. Oh! I decided a couple months ago that Brinefathom will be a GP-for-XP affair, so even with 5e's relatively low XP threshholds, I had to go back and add a lot of treasure. I also started writing the front matter for eventual publication and began populating the island-surface hexcrawl.

If you want to follow someone who's still doing cool daily stuff, I strongly recommend @fishrpg! His blues-themed setting Shadows in the Cotton already has a ton of interesting content, and he's working on polishing and expanding it into a publishable state next year.

In the mean time, thanks to everyone who's bounced ideas around with me this year, especially Fish and the members of the London-in-the-Air discord. Here's hoping I have more updates for you in 2026!

#brinefathom supplementals #megadungeon #listen up me hearties

Guess who somehow neglected to put any stairs between levels 2 and 3 of her megadungeon

#megadungeon #listen up me hearties #brb crying

What's Next for Brinefathom Caves

Happy new year, me hearties!

2024 is over, and Brinefathom Caves is done...ish. The content is there, but it's not really playable in its current state, both because the information is scattered across 366+ Tumblr posts and because I deliberately avoided putting hard stats on anything to avoid getting bogged down. My goal for 2025 is to edit this beast into a playable state, with eventual (e)publication in mind. The finished project will be PWYW--it's nice if someone wants to kick a couple bucks my way, but I'd rather get played than get paid, y'know?

As a proof of concept for this, I've rewritten all the level 1 rooms to a more user-friendly format with stated DCs for checks and saves. Below is a link to a Mega folder with the resulting PDF. It's still very much a work in progress--I haven't done an editing pass beyond spellcheck, for instance.

→ → GET LEVEL 1 HERE ← ←

The list of specific things I want to do this year include:

Rewrite the rest of the dungeon rooms in this format

Create clean digital copies of all maps

Write faction and NPC information for levels 2-6

Expand the minidungeons in the level 4 wavecrawl with playable rooms

Create a small hexcrawl for the surface of the island

Detail the island's port town and some NPCs who live there

Create stats for unique monsters and NPCs

Write procedures for the megadungeon play elements that 5e lacks, like dungeon turns

Probably some other stuff I haven't even thought of yet

So that's, uh, a lot! We'll see how my work ethic holds up without the day-to-day pace of dungeon24, but finishing made me pretty confident in my ability to handle the kind of workload that comes with a large dungeon.

One thing I'm not sure I'll do is go back and do full-map roundups of the lower levels. I really fell off doing that at some point, sorry. Right now, I want to move forward trying to get everything shipshape for publishing rather than spend time on more intermediate content. However, if anyone really missed having those roundups, please let me know. If there's demand for it, I'll happily do the extra work.

If anybody uses material from Brinefathom (especially from the PDF above, but also just in general), I'd love to hear your feedback! I lack the time and resources to playtest a megadungeon, so while I'm doing my best in editing--I swear past me forgot the difference between 4e and 5e encounter balance half the time--having outside perspectives is a huge help.

Finally, thanks again to everyone who followed along for the past year of dungeoncraft. Whether you started reading in January or December, you all made doing this so much more rewarding.

#brinefathom caves #dungeons and dragon #megadungeon #brinefathom caves level 1 #brinefathom supplementals #listen up me hearties

Brinefathom Caves Level 6, Week 8

6.76: The False Demilich

6.77: The Lake of Tears

6.78: The Blood Basin: Basin stained with old dried blood. Refilling it (which requires draining a medium creature or equivalent) causes the wall the basin is on to swivel, opening a one-way secret door for one dungeon turn. Empty.

6.79: The Hot and Cold Doors: Southern half of the room is bitingly cold, northern is baking hot. Metal slab doors only stay open as long as they maintain the opposite temp (hot for southern and cold for northern). Empty.

6.80: The Heavy Weapons

6.81: The Infernal Escape

6.82: The Hanging Doors: Walls painted with frescoes of hanged pirates. Gibbet extends between northern and western doors, which have no keyhole or handles. If a corpse is hung from the gibbet’s noose (regardless of whether it was killed by the noose or not) the door that it faces opens. Empty.

6.83: The Truthful Guards

6.84: The Frozen Leviathan

6.85: The Truthful Dead: Floor carved with runes: zone of truth on entire room. Corpses of two anchor devils who appear to have frozen to death. Empty.

6.86: The Wall of Masks: Northern wall completely covered in devil masks that laugh and jeer when mortals approach them. Ten of the masks conceal buttons, which, if pressed in the correct sequence, open the secret door to 6.87. Only Ukarith knows the correct order, (1-6-8-5-4-9-7-10-3-2) but it can also be gleaned from touching the ice in 6.84. A creature who presses the buttons in the incorrect order must succeed at a Wisdom saving throw or fall prone and become incapacitated and unable to stand for one minute as they’re wracked with laughter. Empty.

6.87: Ukarith's Secret Shrine

6.88: The Tree of Hearts' Desire

(Non-key rambling under cut)

#brinefathom caves #brinefathom caves level 6 #megadungeon #dungeon23 #dungeon24 #dungeons and dragons

Dec 30: The Fruits of Hearts’ Desire

Blood vessels crawl like vines up the curved eastern wall of this chamber and onto the ceiling, where they’ve sprouted 2d4 fruits the rough size and shape of a human heart. The vessels and fruits move and rustle of their own accord. Creatures who approach the eastern wall hear unintelligible telepathic whispering; when they touch a fruit or blood vessel, the whispering becomes clear: Pick your heart’s desire. Ripen and wither.

A mortal who eats a fruit from this room may choose to gain the effect of the wish spell. One who does dies one year after eating the fruit and is reborn as a wretched soul in 6.43 soon after. Nothing (including another wish) short of divine intervention can alter this fate. A mortal who eats the fruit and does not choose to have a wish granted takes heavy necrotic damage. Each subsequent fruit a given mortal eats deals heavy necrotic damage, no matter what that mortal chose the first time.

The fruits have no effect on non-mortals (fiends, undead, etc.). They rot an hour after being picked.

(Non-key rambling under cut)

#brinefathom caves #brinefathom caves level 6 #megadungeon #dungeon23 #dungeon24 #dungeons and dragons

aquamariinaa

#brinefathom inspiration

Dec 29: Ukarith’s Shrine

The walls of this briny-smelling chamber are hung with deep blue draperies, and an image of a monstrous whale (after the leviathan in [AREA]) is painted on the floor and ceiling. In the center of the room is a stone altar, which always feels damp. A chunk of unmelting ice the size and rough shape of a horse’s head sits on a deep blue cloth on the altar, surrounded by a ring of thirteen black candles. Twelve of them are lit; the thirteenth is a candle of invocation that Ukarith intends to use to open a gate to the leviathan’s home in the abyssal ocean.

The ice possesses the same properties as the iceberg it was chipped off of—see [AREA] for details.

(Non-key rambling under cut)

#brinefathom caves #brinefathom caves level 6 #megadungeon #dungeon23 #dungeon24 #dungeons and dragons #listen up me hearties #needs linking

Dec 28: The Infernal Escape

A detailed mural of a recognizable location on the surface of the Whispering Isle covers this chamber’s northern wall. Before it stands a stone altar, stained with blood. If a living creature is killed on the altar, the mural becomes a portal to the location it shows for one hour. A fiend who travels through the portal takes on the appearance of a humanoid and vice-versa. This change is illusory and does not affect a creature’s abilities. It can be removed with dispel magic and similar effects. Any creature who has passed through the portal in the last month automatically sees through the illusion.

(Non-key rambling under cut)

#brinefathom caves #brinefathom caves level 6 #megadungeon #dungeon23 #dungeon24 #dungeons and dragons

Dec 27: The Heavy Weapons

Racks on this room’s walls contain a variety of mundane weapons, as well as a nine lives stealer greatsword and a mace of disruption. All the weapons here weigh 5x as much as ordinary weapons of their type, despite being made of the normal materials.

#brinefathom caves #brinefathom caves level 6 #megadungeon #dungeon23 #dungeon24 #dungeons and dragons

Dec 26: The Lake of Tears

A soft rain of saline tears patters down in this chamber, to the constant sound of crying. The rain collects in a 25’ deep pool, which is home to a despair elemental, a water monster composed of tears that can rip motivation away from living creatures. It only attacks creatures that enter its pool. The floor of the rest of the chamber consists of grey sand.

#brinefathom caves #brinefathom caves level 6 #megadungeon #dungeon23 #dungeon24 #dungeons and dragons

Dec 25: The Frozen Leviathan

A gargantuan, unmelting iceberg dominates this chamber, reaching nearly to the 80’ arched ceiling and stretching down below the floor. It’s wrapped in unbreakable golden chains, which also stretch under the chamber. A massive creature is imprisoned in the ice; what can be seen of it resembles a monstrous, mutated blue whale. Were it freed, it would drown the world and return the oceans to a state of primal chaos. The remit of the devils on this level, beyond torturing the damned, is to ensure that it stays imprisoned.

Any creature that touches the ice must make a Wisdom saving throw or take heavy psychic damage and is afflicted with long-term madness. A creature who succeeds on the save takes half damage and is otherwise unaffected. A creature who fails the save and survives may be granted strange insights or powers by the leviathan while their madness lasts.

The deep devil Ukarith stands next to the iceberg on the northern side of the chamber. She is under the leviathan’s sway and is planning an attempt to free it with a mass sacrifice of other devils, wretched souls, and anyone else unfortunate enough to be on this level. She pretends to be normal and hides the extent of her treachery behind ordinary devilish scheming, but she’s a little too hung up on the leviathan.

(Non-key rambling under cut)

#brinefathom caves #brinefathom caves level 6 #megadungeon #dungeon23 #dungeon24 #dungeons and dragons #another horrible picture sorry

Dec 24: The Truthful Guards

Two anchor devils stand guard on either side of the northern door of this chamber. The floor is etched with runes that form a zone of truth. The devils are under the spell’s effect and do not lie; they know whether other creatures passed or failed their saves. They will not let creatures through the door without a good explanation of what business those creatures have in [AREA], and they interpret a refusal to answer questions as lying. They will attack only if creatures attempt to force their way through the door without permission or in self-defense.

(Non-key rambling under cut)

#brinefathom caves #brinefathom caves level 6 #megadungeon #dungeon23 #dungeon24 #dungeons and dragons #listen up me hearties #needs linking

Dec 23: The False Demilich

The stone altar in this chamber is draped with a crimson runner, on which sits a horned skull with jeweled eyes. Magical black candles burn eternally in tall metal holders on either side of the altar. If a creature approached the altar, the skull’s eyes flash and it levitates a foot in the air. The skull is not a creature but a magic item, a floating skull. A creature attuned to it always floats a foot above horizontal surfaces (ground, water, etc.) and may cast fly once a day targeting themself.

#brinefathom caves #brinefathom caves level 6 #megadungeon #dungeon23 #dungeon24 #dungeons and dragons

Brinefathom Caves Level 6, Week 7

6.66: The Shield of Evil

6.67: The Crying Feathers: Scowling devil faces carved into the walls, floor, and ceiling blow air into the chamber. A couple dozen feathers are caught in the current. If a creature touches one, they’re overcome with a momentary wave of despair. Empty.

6.68: The Devils' Trophy Room

6.69: The Preparation Room: Long table against back wall. Shelves of taxidermy tools—knives, wire, bags of black sand, glass eyes, etc. Empty.

6.70: The Corpse Tree

6.71: The Myriad Hand: Walls look like many huge stone fingers; floor is creased like a palm. When weight is put on the “palm,” the “fingers” close in. If at least 500 lbs. is put on the “palm,” the fingers fully close over the course of a minute and stay clenched for an hour. Creatures in the room have enough time to leave, but the room is rendered impassable until it unclenches. Empty.

6.72: The Other Hands

6.73: The Fountain of Man: Fountain shaped like barfing female human. Salt water, tiny fish with human faces. Empty.

6.74: The Bloody Statue

6.75: The Blood Supplicant

(Non-key rambling under cut)

#brinefathom caves #brinefathom caves level 6 #megadungeon #dungeon23 #dungeon24 #dungeons and dragons #listen up me hearties

The Blood Supplicant

The ceiling of this chamber is colonized by many sleeping fiendish stirges, which will awaken if a loud noise sounds within the chamber. A statue of a barely-humanoid pile of slime sits in the middle, its mouth open in supplication and streaked with traces of dried blood. If the drained blood of a medium creature (or equivalent) is poured down the statue’s throat, the secret door opens soundlessly. If a non-blood liquid is poured in, the statue lets out a horrible shriek, waking the stirges.

#brinefathom caves #brinefathom caves level 6 #megadungeon #dungeon23 #dungeon24 #dungeons and dragons

Dec 20: The Bloody Statue

A lifelike statue of a fiendish ape covered in red fur stands at the end of this corridor. If a non-devil creature approaches within 5’ of it, the statue animates and spins quickly, shedding some of its fur. All creatures within 10’ of it must make a Constitution saving throw or be blinded for a dungeon turn. Once it has done this, the statue attacks and fights to the death, at which point it retains its original appearance and is dormant for a month.

(Non-key credits under the cut)

#brinefathom caves #brinefathom caves level 6 #megadungeon #dungeon23 #dungeon24 #dungeons and dragons #another horrible picture sorry #listen up me hearties

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