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  • Crime and Slime – Sewer Ooze Encounter for D&D 5E
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An encounter with dangerous oozes in the city sewer. Background, battle map, ooze tokens, and 5e stat blocks all included below…

The city’s lower residential district has recently seen the appearance of a fledgling thieves’ guild. This ‘guild’, as it refers to itself, was formed by a small group of local teenagers with a penchant for delinquency and more ambition than sense. They are yet to recruit any additional members. The founding four have managed to establish a small base of operations in the district’s sewers, where they have used their skills as the children of local craftsmen to erect a number of shacks. This hideout is where the group now spends most of their time and amasses the trinkets and scraps that they have successfully stolen.

In truth, most of the guild’s antics have been either minor or fumbled, ultimately amounting to little more than pranks. The neighborhood guards frequently apprehend and scold them, doing what they can to convince the youths of a wiser path, all while preventing word of the thieves from traveling further up the chain of authority. If the higher-ups heard of them, the teens would receive punishments far worse than the people of their district believe they deserve.

But it is the guild themselves, in an attempt to advance their enterprise, that has jeopardized this balance. They stole a crate of experimental tonics from a reclusive local alchemist, Eilis Kelnbrand, who is now publicly calling for the group’s punishment and the return of his product. This has put the guards in an even worse predicament than usual. They cannot arrange a search of the sewers without exposing the guild and none of its members have been seen since the theft. Worse yet, several townspeople heard a horrific screech ringing from a chamber in the sewers not long after the theft. The neighborhood is worried and now offers what little they can, from free accommodation to warm meals, to anyone that would search the sewers, locate the thieves, and return the tonics.

Eilis Kelnbrand

An aged half-orc man steps out, still wearing an apron, work gloves, and goggles raised to his forehead. He grimaces and squints against the light, exposing the darkened pockets under his eyes, and scratches at a gathering layer of stubble.

In a shady corner of the district is the home of the alchemist Eilis Kelnbrand. Eilis is a crotchety old chemist with no patience for others, though he has always assisted the community with remedies and other medicines. His lack of patience is now being tested with the theft of a crate of experimental tonics. Eilis is furious and entirely unconcerned with the protection that the other townsfolk give the thieves.

If spoken to, Eilis angrily stresses the experimental nature of the tonics; his formula was a second-hand recreation of a rough translation and not even he knows what they do yet. He continues to reiterate the importance of locating the tonics before the thieves can misuse them. A character that convinces Eilis to allow them to view the formula can make a DC 15 Intelligence (Alchemist’s Supplies) check to study the tonics. On a success, they deduce that the tonic has no medicinal use and appears to act as a powerful binding agent. On an 18 or higher, the character believes that the tonic may have the potential to animate inorganic matter.

Sewer Hideout battle map - Vertical Preview

The Sewer Hideout

The rickety ladder struggles to hold your weight as it brings you into a barely-lit chamber, where your feet land on the blue-grey stone that makes up the room’s floor and walls. The room widens ahead of you, where it encircles a deep, cylindrical hole. Around the hole are four shacks, constructed from wooden planks and patchwork shades. The same wood has been used to create walkways and bridges that cross over channels of questionably colored water that fill the room with gentle background noise as they flow in channels and pour into the central pit. This water is likely the source of the stinking moisture that fills the chamber, and which you feel staining even the deepest layers of your clothing.

The sewer hideout is a nexus chamber of sewer tunnels that was once infested with overgrown spiders. A group of local teenagers heard of its existence when local guards cleared the spiders out, and thought to take it as their own. It is now the home base of the burgeoning thieves’ guild, where they spend their time, plan their operations, and store their meager spoils. 

The hideout now features four ramshackle buildings that the thieves have constructed. The two smallest shacks have been dedicated to storage, though are currently empty due to the guild’s lack of any real success. The remaining two shelters are used for resting and a living area. A pair of basic hammocks are hung in the smaller of the pair, while the greatest shack holds a table with four wooden boxes acting as stools. Beside the table is a crate with several bottles of alcohol, all mostly empty, perched on top. Against the opposite wall is a pair of boxes covered in mismatched cushions and an old blanket thrown over the top. 

The hideout is currently abandoned, having last been used after the theft of Eilis Kelnbrand’s tonics. As one might expect, the stolen tonics were misused almost immediately upon arriving at the hideout. One of the thieves thought to test the concoction on a patch of mushrooms in the corner of the room, which grew and animated the fungus as a shrieker. The commotion resulting from the shrieker’s sudden appearance and echoing scream led to the remaining tonics being shattered into the surrounding muck and water, some pouring down the central hole. This caused the concoctions to take effect and gave rise to a collection of oozes.

Lighting. The entire hideout is in darkness, except for during the middle of the day when light streams through the grates in the chamber’s ceiling. This fills the room with dim light, with areas of bright light directly below the grates.

Central shaft. In the center of the hideout is a deep, cylindrical pit, into which the channels of water all converge and pour. The pit is 25 feet across and 60 feet deep.

A character that is able to see the bottom of the pit sees a pile of broken planks and wood, which once comprised a bridge that safely spanned the opening of the hole but was destroyed by oozes.

The inside of the shaft still bears a number of spider webs, which help slow the fall of a creature that falls in. A creature that falls down the hole takes only half as much falling damage.

Thieves in hiding. The sudden appearance of a shrieker and attacks from oozes forced the members of the thieves’ guild into hiding. The four of them are now huddled in the two cushion-covered boxes in the largest shack, attempting to remain silent to avoid the creatures finding them. A character that succeeds on a DC 14 Wisdom (Perception) check while within the shack hears a shuffling sound from within the boxes. If the characters do not find them, the teenagers call out once they hear the sounds of combat end, hoping that the noise was someone sent to help them.

Map Downloads

The thieves’ guild’s hideout is modeled after our recent release, the Sewer Hideout, which you can find on its own or with a number of variants These even include one for when your party inevitably ignites an oil ooze and sets the whole chamber ablaze! We also have a number of other assets for expanding the sewers…

  • Sewer Hideout - Basic - Day - 22x16
    Sewer Hideout
    PWYW: $1 or FREE $1.00
  • Sewer Hideout battle map - Variants preview
    Sewer Hideout Pack
    $5.00
  • Sewer Map Assets, Preview 1
    Sewer Map Assets
    PWYW: $1 or FREE $1.00
  • Sewer Battle Map Tiles, Preview
    Sewer Map Tiles
    PWYW: $1 or FREE $1.00
  • Dungeon Room Builder Demo
    Dungeon Room Builder
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  • Dungeon Passages
    Dungeon Passages
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Sewer Oozes

Eilis Kelnbrand’s experimental tonics shattered in the depths of the sewers, binding the muck and collected refuse together and granting it the spark of life. It now crawls forth as a variety of oozes. These slimes have been formed from the wide selection of detritus at the sewer’s bottom, granting them different abilities based on what they incorporated into themselves.

Spike Slime

A glob of orange slime bounces as it moves. Its surface is slick and shiny and bristles nervously at even the slightest touches from objects it passes.

Spike slimes are one of the weakest forms of ooze, yet one that should not be underestimated. Their name is earned from their ability to suddenly reshape their surface in a mass of piercing spikes that impale anything nearby. This becomes all the more dangerous as the slime splits and multiples, filling the area with stabbing attacks from every direction. A skilled fighter can easily evade one, but can they dodge them all?

Venom Jelly

A viscous mound of slime rises and sloshes forward. Its amorphous body is a sickening green that darkens in its center and collects as a liquid on the ooze’s surface, dripping off in beads.

Though the spiders that once lived in the sewers no longer remain, the corpses of a number of them still lay at the bottom of the hole, where some of the tonics fell. Several of the oozes fed on these bodies, becoming two different variants with abilities derived from the spiders.

The first of these ooze variants is the venom jelly, which resulted from the growing oozes finding the spiders’ venom glands. With the glands now inside of them, venom jellies are able to suffuse their bodies with spider venom, secreting it as part of their attacks. This also makes the ooze dangerous for anything attacking it in close range, as the attacker must expose themself to the venom.

Web Ooze

The ooze is translucent white, with an opaque pocket at its core that branches out in strings. As a tendril of the slime’s body begins to stretch, it draws a glob of the white liquid from its center and into the temporary limb.

The second of the spider-based oozes is the web ooze. As its name implies, the web ooze inherited the spiders’ ability to produce adhesive webs as a means of catching its prey. This stickiness also extends to the ooze itself. Melee combatants must be careful when engaging the web ooze or risk it attaching to, overwhelming, and consuming them.

Phalanx Ooze

A blob of light grey sludge takes form, extending and contracting to move. Suspended in its body is a menagerie of rubble, small bones, and everyday refuse such as bottles and broken wood. These items float outwards, roughly arranging themselves in a coating on the ooze’s surface.

The phalanx ooze collects and incorporates items into itself to strengthen its form. This reinforcement adds additional punch to the ooze’s attacks and can also be used to form a protective shell on its surface, protecting the slime within. The phalanx ooze is not picky about what it pulls into itself. One found in a sewer might use discarded garbage and loose bricks, while others may assimilate wood, bones, or even spears and shields. It also has an appetite for the living, as the ooze drags its victims into its mass and traps them within the debris to be digested.

Oil Ooze

Black ooze draws itself together into a single mass. What light that hits the ooze shimmers off of it in blues, greens, and yellows, that swirl like oil on the surface of water.

A byproduct of the sewer and the trash discarded into it is a slick coating of oil and other, more questionable but equally as flammable, material. This gave rise to the oil ooze. Indistinguishable from a discolored regular ooze in most scenarios, the danger the oil ooze presents becomes immediately apparent if it reaches an open flame. Contact with fire causes the ooze to ignite. This fire does hurt the ooze but is just as harmful to its enemies, as the fire coats its body and enhances its attacks.

The oil ooze is a close cousin to our previous mulch ooze, from our ‘Mushrooms, Moss, and Monsters’ article, which contains creatures of living fungi, animated rot, and a strange, log-inhabiting beast…

Balancing the Oozes

The encounter with the sewer oozes does not have any required creatures aside from the single shrieker, which is unlikely to have any impact on combat. This means that you can tailor your choice of oozes to your party. 

If you are unsure about how to approach this, you can begin by choosing a number of oozes equal to the party size and with a total CR matching the characters’ average level. The group can easily escape if this proves too much for them, thanks to the ladder leading out of the chamber. If, however, the party is easily dealing with the monsters and you wish to introduce more, you can have additional venom jellies and web oozes climb up from the depths of the pit using their Spider Climb. You can do the same for oil oozes with their False Appearance by including some puddles of oil in your initial description of the room. If you wish to add them to the encounter and your characters have not confirmed otherwise, they are oozes in hiding. If you end up not needing them, the puddles were always just oil.

Spike slimes and the phalanx ooze do not have the same abilities that allow them to be dynamically introduced. This means that, if you wish to include either of them in your encounter, it is best to factor them into the initial group. This is particularly important for the phalanx ooze, which is CR 2. You can begin with the phalanx and add other oozes to balance the encounter’s beginning, with space to add others depending on how it progresses.

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About the author

Troy McConnell

Part-time DM and author of 2-Minute Tabletop's encounters, map lore, and characters. Basically, I write about all the campaign ideas that I don't have time to run. All with the assistance of my feline familiar, Wink.

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