Walkthrough will follow

01 - Crystal of Life

02 - Sign

Sewer Exit East

03 - Blooddrop Cap

04 - Lever
Opens door to the south and west, shooting poison bolts at you from both sides.

05 - Lightning Bomb (2)

06 - Two-Handed Sword

07 - Sign

Reservoir Access

08 - Sign

Shortcut

09 - Brass keyhole

10 - Sign

Sewer Exit South

11 - Note

ENTER AT YOUR OWN RISK

12 - Ratling Boss
Upon entering this room you encounter a large number of ratlings with the Ratling Boss. By attacking the ratlings the boss also takes damage so deal with them first. Avoid the bosses cannonfire. It causes knockback.

Drops: Handcannon.

Pick up the Brass Key to leave this room again.

13 - Cheese, Potion of Resurrection

14 - Potion of Vitality

15 - Cannonball (1)

16 - Shoes

17 - Brass Key

18 - Leather Brigandine

19 - Skull

20 - Cheese (3), Note

DO NOT DISTURB

21 - Pellets (10)

22 - Sign

Sewer Exit West

23 - Meteor Shield
Once you pick up the shield, the trickster appears and throws firebombs at you. He will drop Firebomb (1) and the Ornate Key, allowing you to open the southern door of this room.

24 - Ornate Keyhole
Opening this door will open the walls across the sewers, containing Fire Elementals.

25 - Greater Healing Potion (1)

26 - Antivenom (1), Smoked Sea Bass

27 - Switch
Opens the door on the right, allowing access back to where you came from.

28 - Scroll, pin puzzle

Follow the leader

What the scroll actually means is: jump down where the pin traps are moving, follow the needles and press the buttons along the way until you hear a door open.

29 - Power Gem

30 - Treasure Chest
Requires lockpicks
Contains: Blooddrop Cap (3), Burrow Rat Shank
Not really worth the lockpick

31 - Secret Button (underwater)
Opens the door at 32

32 - Sack
Contains: Etherweed (2), Blooddrop Cap (2), Falconskyre (3), Mortar and Pestle.
You should already have a mortar and pestle, but would be nice to have a backup when your alchemist gets injured in combat.

33 - Etherweed (1)

34 - Lockpicks (1)

35 - Healing Potion (1)

36 - Diviner's Cloak, Shaman's Staff

37 - Lightning Bomb (1)

38 - Leather Boots

39 - Passage
This area of the map is only reachable by travelling underwater, the gate on the right is open.

40 - Crossbow Quarrel (1)

41 - Island Puzzle
In order to solve this, you need to have the map that you got from the secret treasure you found at the eastern beach at the Hamlet. It draws the shape of the islands in the water in a certain order. Step onto the islands in the order that's indicated on the map, and the door to the northwest will open, allowing you open the treasure.

42 - Treasure Chest
Contents: unknown yet.

43 - Switch
Opens the door behind you

44 - Sack
Contains: Poison Bomb (3), Potion of Vitality (1)

45 - Sewer Garden
You may think it's odd that this sewer has a beautiful garden, but it does, the area is even very rich in fish and it quite quickly regenerates. So if you're ever hungry, you can come fishing here. But that's not the reason you're here... You're here because of what's behind the golden lock.

46 - Crystal Shield