Building a Five Room Dungeon with the Kin of the Rat

In our example, the dungeon is a twisted underground sewer system beneath one of Doaden’s larger cities, crawling with rats and the wretched kin who have made the depths their home. Lately, people have been vanishing from the streets above. Some whisper of orphans walking at night under the pale moon, eyes vacant, steps slow and certain, as if following a tune no one else can hear. Those foolish or desperate enough to search the sewers for them have not returned.

Unbeknownst to the townsfolk, something far more sinister has taken root below. The forgotten children of the slums are being drawn into the undercity, where the Kin of the Rat offer them a new family in the dark. There, hunger, neglect, and stranger influences twist them into Ratkin Foundlings, no longer fully human and fiercely loyal to the burrows that claimed them. The others who disappear are not so lucky. With famine gnawing at the streets above and the tunnels below, they become food for the Kin, their swarms, and the plague-ridden beasts that follow them. Very traditional sewer work, really. Bring boots.

In our example, the party follows a trail of muddy child-sized footprints to a rusted sewer pipe, like the Scrap City Entrance. Torn cloth clings to the bars. Claw marks score the stone. The grate has been barred from the inside, which is never a great sign.

Once the players force a way in, they descend into a narrow passage of foul water, broken masonry, and skittering sounds just beyond the torchlight. The tunnel opens into a flooded junction, where the first guardians arrive: Rat Swarms, pouring from two open sluice tunnels in a squealing tide of teeth.

To make the encounter more than a simple fight, place a rusted floodgate wheel beside each sluice. At the end of every round, any open sluice releases another wave of rats. A character can spend an action to turn a wheel with a successful Strength or Dexterity check, sealing that tunnel and stopping rats from emerging there. Both wheels need to be turned or the party risks getting overwhelmed.

Deeper in the sewers, the party reaches an old overflow chamber where a narrow bridge crosses a circular pit. Below, rats churn around a half-submerged iron idol, their bodies shifting whenever a faint melody trembles through the pipes (which can be shown on the table using a few copies of our Sacred Fountain model).

On the far side stands a locked drainage gate. Three rusted bells hang beside it, each connected to a different pipe running into the walls. Scratched into the stone nearby are the words: “Sing right, or feed the family.”Several Ratkin Foundlings watch from cracks, ledges, and drainage holes, their beady eyes bright in the dark. They do not attack at first. This is a game to them. They whisper bad advice, mimic the bells and throw pebbles. If treated with kindness, bribed with food or cleverly questioned, one of them may reveal that the rats below always move with the correct rhythm.

The gate opens only when the bells are rung in the right order, resonating with the tune echoeing faintly through the tunnels. The correct sequence can be found by watching the rats below: they surge first toward the left pipe, then the right pipe, then the center pipe. That gives the order: left bell, right bell, center bell.Each wrong bell causes the chamber to punish the party immediately. A wrong note makes the rats below surge up through the nearest wall cracks. Spawn one Rat Swarm on the bridge or at the party’s side of the chamber. If the party makes three wrong attempts, the Foundlings decide the game is over and attack as well.

The players can still solve the scene in other ways. They might climb across and force the gate, bribe or intimidate the Foundlings into opening it, block the cracks before trying the bells, use magic to identify the correct rhythm, or distract the rats with food. The goal here is to make the room feel like a hostile little ritual the Kin understand better than they do.

Continuing onwards, the party passes through the bell-gate and finds some of the missing children. They are not chained up or waiting to be rescued, but gathered in a hidden burrow of rags, stolen candles, broken toys, and scraps of food. Some of them still look human, though others have already started changing. Around them, Ratkin Foundlings whisper and hiss little warnings: “No touch.” “Bad uppers.” “Hide it from Brother.”

Then the party notices what some of that “food” really is: familiar bones stripped clean, a torn boot in the muck, a bloodied wedding ring. The missing adults were not taken to be changed, they were taken to feed the family, a scene which can be presented in its brutality with our Bloodsoaked Sewer Grates.

Brother Rat then steps from the dark and places himself between the party and the Foundlings. To the people above, he is one of the monsters stealing their neighbours. To the children below, he is Brother, and Brother keeps the bad things away.

The party can force their way through, but doing so turns the burrow into a desperate fight and proves every story the Kin tell about the cruelty of the world above. If they lower their weapons, some Foundlings may hiss that the “uppers” threw them away first. Others whisper that Nuncle Squeak brings food from above, and that the family gathers when the deep song calls.

That gives the party a way forward: bargain with the Kin, meet with Nuncle to deal with him one way or another, or press deeper toward the thing they call "Oldfather". The setback is that the party came looking for victims and monsters and found both huddled under the same filthy blanket.

If the party decides to press on, they finally reach Nuncle Squeak. If they dealt peacefully with Brother Rat and the Foundlings, they are led through narrow side-passages under hundreds of glittering eyes. If they chose violence, they arrive the ugly way, fighting through the burrow until the tunnels open into Nuncle’s market-den.The place is part throne room, part junk stall, part family pantry. Rotten planks sag over black water. Stolen icons hang beside strings of teeth. Cages, Sacks and Crates, and half-sunken carts form crooked aisles of scavenged treasure and things best not inspected too closely.

At the center waits Nuncle Squeak, fat, old, and sharp-eyed, perched atop his hulking plague-rat mount. He greets the party like guests, even if they arrive covered in his family’s blood. “Come then, uppers. Talk nice, or squeal loud.”

This climax can become a bargain or a battle. If the party talks, Nuncle offers what he has: safe passage, names of those above who sell captives, and the tunnel that leads toward the deep song. In return, he may ask for food or protection and a promise that the party will leave the burrow standing.

If they refuse, the market turns against them. Rat Swarms spill from crates, Foundlings cut ropes and drop cages and Nuncle surges towards the party on his mount. He does not fight fair. If he notices that he's on the losing end of the conflict, he bargains while retreating, uses hostages for time, and tries to vanish into the tunnels. The party’s goal will be to stop Nuncle from escaping and force him to call off the Kin so they can push deeper. If he gets away, they can still follow the music, but with no guide, no bargain, and every tunnel behind them turning hostile.

However it ends, Nuncle leaves them with the same truth: he feeds the burrow, but he did not make the song.When the market falls silent, the music is still there, faint and patient, rising from somewhere deeper.

After Nuncle’s market-den, the party follows the music deeper, past the last lanterns, the last voices, and the last places where the sewer still feels built by human hands.

The tunnel ends in an ancient cistern, half-flooded and impossibly still. Old brickwork disappears beneath layers of gnawed wood, rags, bones, candle stubs, and rat skulls pressed into the walls like offerings. At the far end stands a shrine made from sewer grates, broken cradles, stolen holy icons, and little toys tied together with hair and wire. Among the offerings, the party can find their reward: stolen coins, charms, relics, keepsakes from the missing, or some strange object the Piper’s children thought precious enough to bring below.

Around it wait the Enthralled Urchins, silent and barefoot in the black water. Their eyes are empty, but their faces are peaceful. That is the worst part. They look as if, for the first time in their lives, someone has finally called them home.

Before the shrine stands Oldfather, The Piper Beyond: a tall, ragged figure beneath a pointed hood, bone flute pressed to unseen lips. Rats crawl through the folds of its robe. Little bells hang from crooked fingers. Small limp shapes cling to its back like children carried by a parent.

The party has three obvious choices. They can talk, but Oldfather does not answer. It only plays, because this is not a creature seeking conversation. It is a hunger wearing the sound of comfort.

They can attack, shattering the bone flute and breaking the song. Oldfather collapses into a flood of rats spilling from its robes, scattering into cracks, pipes, and black water. The manifestation is gone, but the thing behind it is not dead.

Or they can rescue the Urchins, pulling them from the water before the song finishes. If they do, the music falters. The children wake screaming, the rats scatter, and the Piper withdraws into the dark beyond the shrine. The song does not end, not truly. It only grows distant for now.


However they act, the final revelation is the same: the Kin are not just monsters in a sewer. They are what grew in the dark after the city threw its children away, and something ancient was waiting there to call itself Father. The dungeon may be over, but Oldfather may rise again wherever hunger, neglect, and loneliness leave children listening for a kinder voice in the dark. And next time, it may not be so kind as to let the party leave with only the song in their heads.

So ends this adventure, but there is a lot of room to develop this into a larger arc throughout a larger campaign where the Piper Beyond could become a recurring threat. 

As a reminder, if you'd like to run this encounter at your table, make sure to check out our Kin of the Rat Faction Pack for a wealth of resources such as 5E statblocks, lore and artworks to truly bring it to life.

Hopefully you enjoyed this dungeon showcase, let us know your thoughts below and make sure to drop us a comment if you decide to run the adventure for yourself!