Toxic Sewers

Access and exit
The Vine rune is required to access this biome through the Prisoners' Quarters.

Three exits lead out of the Toxic Sewers: one takes the Beheaded back to the surface atop the Ramparts, the other leads further underground to the Ancient Sewers, and third leads to the Corrupted Prison.

Accessing the entrance to the Ancient Sewers requires the use of a Ram rune, and accessing the entrance to the Corrupted Prison requires the use of the Spider rune. No runes are required to access Ramparts.

Teleportation rune
An Elite Slasher can be found here which drops the. It disappears after being defeated.

Scrolls
The Toxic Sewers contains 3 scrolls, including 1 Power Scroll and 2 Dual-stat scrolls. Scrolls cannot spawn in areas requiring the Teleport, Ram or Spider runes. On (1+ BSC) there is a bonus Power scroll. When 3 BSC are active, this biome has 2 guaranteed Scroll Fragments, and when 4/5 BSC are active, this biome has 3 guaranteed Scroll Fragments.

Main level

 * There is a 10% chance for a Cursed chest

Boss Stem Cells rewards

 * 1 BSC: Treasure chest

Secret areas

 * The blueprint for the mutation can be found in the Collector transition area between the Prisoners' Quarters and the Toxic Sewers.
 * The blueprint for the mutation can be found behind the 2 minute timed door in the same transition area.

Enemies
In the Toxic Sewers, you will find plenty of Kamikazes, Disgusting Worms, and Scorpions, which are the iconic enemies of this level. In addition, Zombies, Undead Archers, and Grenadiers dwell here. On higher difficulties, Festering Zombies, Knife Throwers, and Rampagers make this stage even harder. The Toxic Sewers do not have any unique enemies.

In the table below, you will find which enemies are present in the Toxic Sewers depending on difficulty level. For each enemy, any common, uncommon, rare or legendary blueprints they carry are indicated. When applicable, the minimum difficulty level for blueprint acquisition is specified in brackets.

Conjunctivius


A series of lore rooms scattered around the Toxic Sewers and Ancient Sewers explain how Conjunctivius came to be.

It begins with a nameless, faceless corpse in the Sewers, likely infected by the Malaise. The body is bloated and one of its arms has mutated into a tentacle. :


 * "The body is all bloated... One of his arms changed into a tentacle."
 * "It's as if the body had started to mutate!"

Green goo trails from the body:


 * "A viscous substance is oozing out of the body and across the floor... like a snail's trail."

Towards a small hole in the wall.


 * "... the trail leads to the hole."
 * "I don't know what it is, and I don't really want to know."

After this encounter, the Beheaded finds the same trail of green goo:


 * "Nothing special here..."
 * "... except this strange substance on the ground again."

And an empty cocoon:


 * "The trail leads to a sort of... giant cocoon."
 * "All sorts of unspeakable horrors lived here."
 * "It's really revolting."
 * "I'm not feeling too fresh after that either."
 * "... After all, who am I to pass judgement?"
 * "... I haven't even got a head. I don't even know where I come from."
 * "Might this cocoon be the very symbol of our existence?"
 * "Futile, ephemeral?"
 * "Aren't we destined to adapt or die, in this ineffable loop we call life?"
 * "After all, what is life? And what about love?"
 * "An inexorable series of moments stolen along the way, at the dawn of..."
 * "Yeah, OK, boooooring!"
 * "An inexorable series of moments stolen along the way, at the dawn of..."
 * "Yeah, OK, boooooring!"

Next to it, is a bigger hole in the wall, which was made by an adolescent Conjunctivius :


 * "The trail ends at this hole."
 * "And it's one hell of a big hole."

Later, the Beheaded stumbles upon the trail of green goo near a corpse:


 * "A body in prisoner's clothes. Maybe he tried to escape through the sewers?"
 * "...He's got lots of wounds but he doesn't seem to be infected."
 * "Hmm..."
 * "Rest in peace."

The trail leads through a hidden passage, halfway that passage, the Beheaded stumbles upon some crates:


 * "I don't quite get what these crates are doing here, but so be it."

The trail leads to the remains of a huge cocoon:


 * "Whatever this thing is, it's pretty obvious that it... grew."
 * "Or evolved."
 * "Or mutated."
 * "In any case, I've got a bad feeling about this."

And a gigantic hole, carved by the adult Conjunctivius as she escaped:


 * "That thing didn't waste any time getting out of here."
 * "Must be a cute and cuddly little thing by now!"

Finally, a message left by soldiers tells how difficult it was to chain Conjunctivius, likely an order of the King. This explains why Conjunctivius is imprisoned in the Insufferable Crypt when the Beheaded arrives.


 * "Looks like a warning message from a guard."
 * "It's written in red so it must be important."
 * "Make sure you don't miss your guard duty outside the MONSTER's room..."
 * "It wasn't easy to chain up. Wouldn't like to have to do it all over again!"

Malaise
The Sewers seem crucial to the spread of the malaise, through its water supply system. For example, piles of contaminated bodies are found rotting in the sewer water. The Beheaded questions if the bodies are responsible for the initial infection of the citizens, or they only helped spread the Malaise by contaminating the water network:


 * "Some contaminated bodies leaked into the drainage lines... and that must have contaminated the whole water network."
 * "But was the water contaminated before the first citizens fell ill?"
 * "Hmm..."
 * "Which came first, the chicken or the egg?"

A giant broken door is found next to a soldier’s note warning not to open this door, lest the rats get out and spread the Malaise. The Beheaded remarks that it is unlikely rats made such a big hole, which implies something else was kept behind the door :


 * "Keep this door locked at all costs! If the rats get out, they will spread the Malaise!"
 * "Rats are always a prime suspect in times of illness"
 * "I don't know, I kind of like rats."
 * "And I'd be surprised if it was rats that made a hole like that."
 * "And I'd be surprised if it was rats that made a hole like that."

Additionally, the beheaded notes how the door was solid before being broke down:


 * "It looked solid before it was broken down."

The corpse of Prisoner 236 is found close by; he presumably died while trying to escape:


 * "Prisoner 236"
 * "The body doesn't look contaminated."
 * "But how did this prisoner end up here?"
 * "Another failed escape attempt!"

Alchemist grimoires
In the Sewers and the Ancient Sewers, the Alchemist collected mold and mushroom samples for his experiments. However, the growing numbers of revenants made his work increasingly difficult:


 * "It is becoming increasingly difficult to collect mold samples in these sewers."
 * "There are too many revenants."

Gollum and the Teleportation Rune
When the Beheaded first enters the Toxic Sewers, he meets an unnamed character (called "Gollum" in the game files, a reference to The Lord of the Rings) stuck behind bars who asks him to fetch "his" rune — heavily implying it does not truly belong to him:


 * "HEY YOU!"
 * "Come here for a second!"
 * "A little slow... But you seem to understand what I'm saying..."
 * "I lost a ru.. I mean MY rune. So you see, I'm a little stuck..."
 * "And I NEED my rune, you see..."
 * "You wouldn't mind finding it for me, would you?"
 * "Ho ho! Thank you! It's somewhere around here in these sewers, on your side of these bars..."

When the Beheaded kills the Elite Slasher who holds the rune, he later encounters the mysterious character again but refuses to return the rune. "Gollum" then warns the Beheaded will regret this and swears he will eventually get his rune "back":


 * "Hey, over here!"
 * "I saw your fight. It was pretty impressive."
 * "Did you...? Did you get it?"
 * "Excellent! Now give it to me!"
 * "I said... GIVE IT TO ME!"
 * "I knew it... You're just like all the rest..."
 * "You'll regret this..."

A lore room full of teleportation monoliths can be found with his crushed corpse, putting a sad end to this story:


 * "The tombstone dropped from the ceiling and..."
 * "Dammit!"
 * "I recognize this hand."
 * "The poor guy couldn't escape fate. His lair became his tomb."

It's also explained why 'Gollum' wanted 'his' rune back: a teleportation monoliths leads to a treasure chest full of treasure, assumed belonging to 'gollum':


 * "Hmm, I understand now why he wanted his rune back."

Due to a bug, the room continues to spawn in the biome even in future runs, regardless of the player obtaining the rune or not.