Lower Undead Burg

The narrow streets below the Burg, reached with the Basement Key. The Capra Demon guards the way down to the Depths.

Bosses

Capra Demon: Run up the stairs on the left at once to escape the two dogs, kill them, then fight the demon. Drops the Key to Depths.

Bandit's Knife: Thief starting weapon; rare drop from the Undead Assassins in Lower Undead Burg.
Mail Breaker: In the first room on the right where the Undead Thieves ambush you in Lower Undead Burg.
Target Shield: Thief starting shield; on a corpse in a small room just before the Capra Demon in Lower Undead Burg.
Thief Mask: Thief starting gear; in the room with the second group of thieves in Lower Undead Burg.
Black Leather Armor: Thief starting gear; in the room with the second group of thieves in Lower Undead Burg.
Black Leather Gloves: Thief starting gear; in the room with the second group of thieves in Lower Undead Burg.
Black Leather Boots: Thief starting gear; in the room with the second group of thieves in Lower Undead Burg.
Sorcerer Hat: Sorcerer starting gear; break the barrel in Griggs's room in Lower Undead Burg.
Sorcerer Cloak: Sorcerer starting gear; break the barrel in Griggs's room in Lower Undead Burg.
Sorcerer Gauntlets: Sorcerer starting gear; break the barrel in Griggs's room in Lower Undead Burg.
Sorcerer Boots: Sorcerer starting gear; break the barrel in Griggs's room in Lower Undead Burg.
Hollow Thief's Hood: Dropped by Undead Assassins in Lower Undead Burg.
Hollow Thief's Leather Armor: Dropped by Undead Assassins in Lower Undead Burg.
Hollow Thief's Tights: Dropped by Undead Assassins in Lower Undead Burg.
Key to Depths: Dropped by the Capra Demon.

First unlock the shortcut that climbs back to the Undead Burg.
Open the locked house with the Residence Key to free Griggs of Vinheim, then roll through the barrels to get the Sorcerer Set and the Sorcerer's Catalyst.
Scattered through these streets: Twin Humanities, the Mail Breaker, the Thief Set, a Target Shield and a soul.
Defeat the Capra Demon: run up the stairs on the left at once, kill the dogs, then turn on the demon. It drops the Key to Depths.
Optional co-op around levels 20–30.
Go down the stairs and up the left tower to the Undead Merchant (Female). Stock up on Purple Moss Clumps and Blooming Purple Moss Clumps for Blighttown, Transient Curses for New Londo and Homeward Bones.
Unlock the gate that connects these streets to Firelink Shrine.
Talk to Griggs of Vinheim at Firelink Shrine, say yes and buy any sorceries you want.
The Crestfallen Warrior has a fresh line for you; hear him out.
Talk to Knight Lautrec of Carim at Firelink Shrine to get a Sunlight Medal.
Optional: kill Lautrec now to save Anastacia later and take the Ring of Favor and Protection, at the cost of his set.
Back on the aqueduct, take the tower down and walk across to the tower that leads to the Depths.