Valley of Drakes is an optional area you can visit from multiple locations within Dark Souls.
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Valley of Drakes
If you have the Master Key when you start, you will be able to access the Valley of Drakes straight from here, the enemies here are pretty difficult, so we recommend that you only come to clear the area after you have placed the Lordvessel.
For the purposes of this guide, we'll be coming at The Valley of Drakes from the gate at the start of New Londo Ruins at the start, which can also be easily followed from Blighttown.
The first thing that you will notice about the Valley of Drakes is that it is incredibly narrow, meaning that it'll be very easy to fall off without much warning. Because of this, get a greatshield with good stability if you are nervous about traversing this area. Immediately in front of you will be an entrance to Blighttown, which is passable through a small wooden bridge.
Ignore the wooden bridge for now and hug the left side of the wall. At the end of this path will be a Witch's set and Beatrice's Catalyst. Then, make your way back and across the wooden bridge. Then, you will want to hug the right wall until you come to a more sturdy-looking wooden bridge. Cross it and proceed forward until you are met with a slumbering Dragon.
Before gunning for anything else, you're going to want to take out this Dragon. So let's first talk strategy. This Dragon will not attack you unless you talk towards the items it is guarding. The Undead Dragon is able to spew Toxic Sludge at you, which will make your health go down startlingly quickly. In addition to this, it also has a claw attack and a bite. While initially intimidating, there is an incredibly easy strategy to kill this miniboss.
Slowly walk towards it until it decides to spew some sludge, it should miss, then head in while two-handing your weapon and you should be able to get in a hit, retreat, and rinse and repeat. This is the most reliable way of easily killing the Undead Dragon, and it'd help if you had a strong weapon, too.
Once it's down, pick up the Astora's Straight Sword, Dragon Crest Shield and Soul of Proud Knight in front of you. Then, proceed forward until you meet your first Drake. Due to the narrowness of the ledge in front of you, you want to roll with a high stability shield and watch out for its electrical attacks. If you head into the cave on the right, you will find one Humanity on a corpse.
Then, proceed forward and kill another Drake on the open area. If you head up the incline and to the left away from the bridge, you will encounter the path to Darkroot Basin. Go back and start to cross the bridge.
This Drake will be in front of four more, so you will want to kite them out onto the bridge to kill them one-by-one. The item on the bridge is the Bridgand Set with Spider Shield, if you proceed forwards from here you will reach New Londo Ruins, if you have opened the gate from the other side.
There's not a whole lot to this area, aside from connecting a few areas together, it has no end-boss.