Caustic Sewers

Caustic Sewers, also known as CS, is a dungeon found in the Tanren Undercity. The green water in this dungeon can poison a water, flying, or levitating Pokémon, so bringing a Pokémon with Refresh will help you throughout this dungeon.

Scenery
Lower Floors Middle Floors Upper Floors
 * Floors 1-11Sewerslow.png
 * Floors 11-20Sewers.png
 * Floors 21-30

Pokémon
The Pokémon here are mostly Poison, Ghost, Dark, and Steel.

Lower Floors(1-10):

These floors are mostly pre-evolved pokémon and mid-evolved pokémon. Middle Floors(11-20):
 * Koffing
 * Ariados
 * Nidorina
 * Nidorino
 * Golbat
 * Haunter
 * Skorupi
 * Seviper
 * Arbok
 * Bronzor
 * Stunky
 * Raticate
 * Gulpin

A few fully evolved pokémon like Gengar and Weezing. There's still a few pre-evolved and mid-evolved pokémon. Upper Floors(21-30):
 * Gengar
 * Stunky
 * Weezing
 * Ariados
 * Arbok
 * Nidorina
 * Nidorino
 * Crobat
 * Forretress
 * Raticate
 * Koffing
 * Grimer
 * Muk
 * Seviper
 * Haunter
 * Duosion
 * Venomoth
 * Swalot
 * Garbodor
 * Dustox (Night)

The upper floors have many fully evolved pokémon and you can recruit a Trubbish on these floors at Dusk/Night. Also, you can find Trubbish eggs, but they're rare. Mystery Eggs:
 * Nidorina
 * Nidoqueen
 * Nidoking
 * Bronzor
 * Drapion
 * Swalot
 * Stunky
 * Muk
 * Ariados
 * Garbodor
 * Ferrothorn
 * Trubbish (All times)
 * Weezing
 * Bronzong
 * Trubbish (Rare)

Items:

 * Relic Copper
 * Relic Silver
 * Relic Gold


 * Ekop
 * Rotten Apple
 * Kebia Berry
 * Grimy Food
 * Grimy Berry
 * Cleanse Orb
 * Recycle Orb
 * Trawl Orb
 * Mobile Orb
 * Oran Berry

Boss
The boss is a resemblance to Team Skull from Explorers of Time/Darkness/Sky, which are Skuntank, Koffing, and Zubat. Skuntank drops 35 Ekops when it's defeated. Koffing and Zubat drop 1 Tiny Mushroom each.
 * Skuntank
 * Koffing
 * Zubat

Dungeon Objective
As with most dungeons, the goal is to complete it and go to Ancient Caustic Sewers. Caustic Sewers is also a location where a Pink Silk may be obtained. This can be accomplished by unlocking the Sealed Chamber on 25F with a Silver Key and having the contents of the box contained appraised. Secret Room: Ending box:
 * TM Toxic
 * Poison Dust
 * TM Venoshock
 * Full Restore
 * Big Nugget
 * Max Revive
 * Purity Relic

Tips
Bring a Pokémon with Refresh.

Purity relic/Safeguard/Status immunity gems are recommended.

There is a kecleon shop at 28f

Trivia
Caustic Sewers has one of the highest level ranges out of all the Tanren Undercity dungeons.