Ancient Sewers

Access and exit
The Ancient Sewers can normally accessed from the Toxic Sewers after obtaining the, or from the Corrupted Prison after obtaining the Spider rune. When playing with 1 or more BSC active, a door in Prison Depths can also lead to this biome, though it requires the.

The only exit out of the Ancient Sewers leads to the Insufferable Crypt, where Conjunctivius awaits.

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

Enemy tier and gear level scaling
In the table below, you will find the gear level and enemy tier of the Ancient Sewers based on difficulty.

Main level

 * 10% chance for a cursed chest

Boss Stem Cells rewards

 * 1 BSC: Treasure chest
 * 2 BSC: Treasure chest
 * 3 BSC: Treasure chest
 * 4 BSC: Chained items altar

Secret areas

 * The blueprint for the can be found in a secret area with poisonous water. The player must roll through a hidden path in the walls where the blueprint is located. This secret area will always be covered in poisonous water and there is no way of avoiding it. Damage can be prevented, however, with an amulet granting immunity to poison.
 * The blueprint for the can be found in a puddle with poisonous water that has a fake floor. The player must slam their way down to obtain it. Alternatively, the player can use the  to retrieve it, without taking damage from the poisonous water.
 * The blueprint for the upgrade can be found in a secret area concealed by cosmetic ground tiles with a maze that can only be navigated by the . The player must first open the door with the rune's help, then progress downwards and solve another puzzle, before reaching the blueprint.

Enemy blueprints

 * The blueprint for the can be looted from Impalers.

Enemies
Many enemies are common between the Toxic and Ancient Sewers, including Disgusting Worms, Kamikazes, Scorpions and Zombies. A unique feature of the Ancient Sewers is the presence of the Impaler, which can sprout highly damaging spikes from the floor, remotely aiming for the player in a wide range, and usually does not spawn anywhere else. Apart from Zombies, which are replaced by Failed Experiments on 4+ BSC, all other enemies are present at all difficulty levels.

In the table below, you will find which enemies are present in the Ancient 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 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!"

Alchemist grimoires
In the Toxic and Ancient Sewers, the Alchemist was collecting 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."

Other rooms
Found in a secret entrance (may not spawn in every run), the room contains a corpse in the background, a campfire, and some wall scratchings that The Beheaded read as "GIT GUD". Upon interacting with the campfire, he will say "Something seems to be changing". Returning to the exit after interacting with the campfire will cause a Zombie or an Undead Archer to spawn. When killed, this enemy will drop 50 cells.

Trivia

 * This biome is named "Old Sewers" in the past versions of the game.