Need a quick swamp dungeon? You can follow this five-step random generator to create an entirely random dungeon shell you can fill in and personalize until your heart's content!
The entries are deliberately somewhat vague to allow more GMs to use them, as they’re open to incorporating varieties of monsters with varieties of challenges on most outcomes.
While these reference monsters from D&D, the results can work at most fantasy RPG systems beyond D&D.
1. Where is the Dungeon?
The following table determines where the dungeon is within a swamp environment:
Swamp Dungeon Location Table
| d20 | Location |
|---|---|
| 1 | In a clearing of weeping willows growing over murky waters |
| 2 | Within an inlet a flooded inlet where snapping turtles nest |
| 3 | Centered inside a wide lagoon home to corrupted gators |
| 4 | Jutting out from a wide field of reedbeds |
| 5 | In a beautiful mire coated in vibrant rare flowers |
| 6 | Below a dense canopy of mossy trees that leave it dim all throughout the day |
| 7 | Stuck in a bog releasing bubbles of bursting gas that ignite into haunting colors |
| 8 | Centered in a mysterious circle of large stones etched with glyphs of a lost language |
| 9 | Deep within a treacherous woodland spider nest covered in webbing |
| 10 | Below a labyrinth of mangrove tree roots bursting from the waters, burying it |
| 11 | Hidden within a mile-wide radius of dead or dying foliage coated in a black moss |
| 12 | Across a miserable boneyard half submerged in muck, traversable by bone path |
| 13 | Nestled in a buzzing hotbed of mosquitoes and other swarms of bugs |
| 14 | Beside a deserted town ruined by rising waters and sinking ground |
| 15 | Atop a long rocky formation in the odd form of a dragon from the swampland |
| 16 | Through a dank series of tunnels dotted with dangling tree roots and glowing worms |
| 17 | Within a dark pool of water that shimmers with oil-like colorful streaks |
| 18 | In a wide, sparse landscape coated in deep mud and sparse massive drooping willows |
| 19 | Dug into a hillside and locked behind thick root bars drooping over the entrance |
| 20 | Lost in a maze of thick trees, high waters, and dense fog |
2. What is the Dungeon’s Purpose?
The following table determines the builder’s purpose for this dungeon:
Swamp Dungeon Purpose Table
| d12 | Purpose |
|---|---|
| 1 | The dungeon was a hideout for pirates who fled inland from the nearby waterways |
| 2 | The dungeon housed brutal beastial rituals to expedite unnatural evolution |
| 3 | The dungeon offered ample access to deadly ingredients for a dangerous alchemist |
| 4 | The dungeon prevents an ancient and powerful witch from escaping the swamp |
| 5 | The dungeon was built prior to the swamp’s growth to claim land for a warlord |
| 6 | The dungeon was a tyrant’s bastion to control the swamp’s denizens |
| 7 | The dungeon provided a recluse with a hideaway as they were driven to insanity |
| 8 | The dungeon gives a necromancer easy access to corpses as travelers perish around it |
| 9 | The dungeon acts as an outpost for illegally trafficked slaves and other illicit cargo |
| 10 | The dungeon houses objects that poisoned the land and killed the dungeon’s creators |
| 11 | The dungeon initially acted as a hub for a joyful druidic meeting prior to a disaster |
| 12 | The dungeon hid a wrongfully convicted hero, eventually tracked down and murdered |
3. What is the Dungeon’s Structure?
The following table determines a general structure you can use to build your dungeon:
Swamp Dungeon Structure Table
| d12 | Structure |
|---|---|
| 1 | An overgrown castle with flora bursting from the walls and towers |
| 2 | A lone watchtower whose bottom three floors have sunk below the marsh |
| 3 | An eerie multi-story mansion built decades ago overrun with pests |
| 4 | A pristine domed cathedral, notably clean of any influence from the surrounding swamp |
| 5 | A four-room wooden home with a cheery chimney and cellar door |
| 6 | A once abandoned tavern with a thick tree bursting through its roof |
| 7 | A village interconnected by tunnels branching below the earth leading to dark secrets |
| 8 | A majestic vineyard well maintained and growing flourishing deadly berries |
| 9 | A fortress split and lifted off the ground connected by the enormous trees holding it up |
| 10 | A bustling bazaar full of ruffians and scoundrels housing the villain’s plots |
| 11 | A monastery to a false god with shattered glass windows, flora taking over its form |
| 12 | A half-sunk graveyard and stone mausoleum lit by floating eerie orange lights |
4. Who Currently Resides in the Dungeon?
The following table determines what kinds of creatures reside in the dungeon:
Swamp Dungeon Creatures Table
| d20 | Creatures |
|---|---|
| 1 | Undead spirits from the dungeon’s founder and surrounding locals |
| 2 | Yuan-ti cultists collecting sacrifices for their hungry old gods |
| 3 | A chained angel gone mad using divine traps to judge and punish any who enter |
| 4 | Bullywug rebels, once oppressed by a tyrant, now owners of the dungeon |
| 5 | Human outcasts having taken the dungeon as a final bastion for their ideology |
| 6 | Fey pranksters that use the swamps mysterious lights to play tricks on travelers |
| 7 | Devils stuck within the dungeon after a deal they crafted with a wizard ended in disaster |
| 8 | Water and earth elementals composed of the mud and waters that surround the dungeon |
| 9 | A vile green hydra and the scavengers who pick over whatever is left from its meals |
| 10 | Goblins using the dungeon as a hideout beyond where the law will pursue them |
| 11 | Oozes that embody the spirit of the swamp itself who occasionally take humanoid shape |
| 12 | Giant spiders with unnatural intelligence who tempt humanoids in with treasures |
| 13 | Bog zombies coated in fungus and plant life, half plant, half undead |
| 14 | Constructs altered by the overgrowth, defending the dungeon at all costs |
| 15 | Trolls reigning from their dungeon over the other fearful swampfolk |
| 16 | Beasts enlarged by odd fey magic, including giant toads and crocodiles living in harmony |
| 17 | Demons bound to the dungeon by a warlock’s last curse |
| 18 | Harpies nesting atop the dungeon and nearby trees who ambush unaware travelers |
| 19 | A black dragon lounging in muck and their conscripted black kobold underlings |
| 20 | A green hag nature coven who’ve bolstered their lair with megafungi |
5. What Rooms Are in the Dungeon?
Consider either rolling as many times as you’d like ahead of time to plot out the dungeon, or rolling as the players progress through where the new doors may lead. There are two options: an ordinary rooms table, for when you want the players to explore some mundane options, and extraordinary rooms for when you want to spice things up a bit.
The following tables can be rolled on to determine what rooms the players encounter as they progress:
Swamp Dungeon Ordinary Rooms Table
| d10 | Ordinary Room |
|---|---|
| 1 | Guard garrison and armory with bunks and weapon racks alike |
| 2 | Kitchen, overrun with fungus, mold, and plant life seeping through the walls |
| 3 | Storage room, kept sealed as best possible containing dry goods |
| 4 | Infirmary, cleaned up now, but clearly recently thrown apart by an angry cadaver |
| 5 | Prison cells with a lair of fetid water coating the floors, rife with parasites and insects |
| 6 | Conservatory containing overgrown plantlife bursting from their pots and planters |
| 7 | Washroom/bathhouse running swamp water through an elemental purifier |
| 8 | Vault with condensation dripping from the roof onto the damaged paintings and art within |
| 9 | Recreation room lit by a lone flickering lantern with a pair of card tables and billiard table |
| 10 | Dining hall with long warped wooden benches, floor coated with debris and muck |
| 11 | War Room with shriveled, poorly maintained maps on a shoddy central table |
| 12 | Trophy room with head trophies surrounding a central taxidermied giant crocodile |
Swamp Dungeon Extraordinary Rooms Table
| d8 | Extraordinary Room |
|---|---|
| 1 | Ritual chamber with sacrificial pits connected by magical roots into a central basin |
| 2 | Workshop, well kept by a construct radically burning away plantlife that enters the space |
| 3 | Temple to a snake deity with a stone serpent statue with an open mouth leading deeper |
| 4 | Gladiatorial arena half submerged in water, littered with corpses from prior matches |
| 5 | Crypt with shelves dug into the muddy walls, the coffin lids having broken out from within |
| 6 | Puzzle room with a locks releasing water between chambers, releasing giant insects |
| 7 | Insectoid hatchery with clutches of giant, odd stick eggs coating the walls |
| 8 | Magical library whose bookshelves raise and lower into the mud on command |
