How to get to Demon Ruins
So proceed down from Quelaag's Domain and into this fiery hellscape.
Immediately, you're going to notice that the majority of this area is covered in the egg-infected people and lava. You want to look right and towards the small walkway leading to a fog gate and your next boss fight.
Make your way down there, ignoring the rest for now, and pass through the fog gate to fight Ceaseless Discharge.
Exploring Demon Ruins
Once Ceaseless Discharge is down, head down and towards the new area that has been drained of lava, if you head slightly to the left, you will see that the Taurus Demon has made a triumphant return as a normal enemy.
There are a few of these, so bait them out with a ranged attack using a bow or Soul Arrows. They are not too hard to kill, they go down in 2 hits with shots from out +14 Zweihander, and they all have the same moves as the boss.
Clear these Taurus Demons out to make navigating this area a little easier. The Taurus Demons are weak, there are just a lot of them, so divide them up and take them out. Then, you want to head all the way down the path that the Taurus Demons were guarding to find a corpse in lava. Here is the Chaos Flame Ember, which you can give to Vamos. Then, head back up, on the right will be an item on a corpse, which is a Soul of Proud Knight, if you can get it.
Then, go back up the path and hang left, until you see another familiar enemy- Capra Demon! Take this out and head past the area he was guarding. Head down the stairs untl you eventually encounter an area with 5 Capra Demons, again divide and conquer, try to stay put and dispatch of all the Capra Demons without aggroing the others. You can use the stairs up as bait to try to kick Capra Demon off of the ledges, but Melee works best here.
Head down the stairs and you will encounter a Fire Slug, which is surprisingly tough, take it out quickly and do not let it breathe fire on you. Then, go back and towards the building you are in until you see a monster poking out of the wall.
This monster is pretty strong, and its writhing attacks can knock you back if you're not careful. Defeat this to unveil a bonfire. There is a Soul of Proud Knight just ahead, then go towards the walkway that we ignored before. AS you head down the stairs, you're going to want to take out the fire slugs that you encounter.
Progress forward and then the Taurus Demon will aggro, take care of this and head to the bottom of the stairs, where another wall centipede will emerge. Kill this, and be careful of the terrain as it can easily hit you off. After killing this, head left to kill another Taurus Demon, kite this out and up the stairs for some more stable footing.
Then, follow the path down, kill another Taurus Demon and head along the path until you see another Centipede, kill it, then head forward to be faced with 4 Centipedes, retreat and take these out at range, then in a chest you will find the Large Flame Ember, which you can give to Vamos.
Head back and to the bottom of the stairs once more. Head up and to the right to kill a Capra Demon and get a Soul on the ground, then progress towards the Fog Gate, but head right at the opening. If you have the Daughter of Chaos Covenant levelled up to 30, you will find a shortcut into Lost Izalith.
If you're looking for more help, our Dark Souls walkthrough and guide can help with all other areas of the game, including the dreadedTaurus Demon, Capra Demon, Ornstein and Smough bosses. Meanwhile, we have explainers on how to access DLC Artorias of the Abyss, the best gift and best class in Dark Souls, Dark Souls' best weapons, Dark Souls Covenants, Dark Souls Estus Flasks locations, Dark Souls Titanite Slab locations and NPC quests including Lautrec of Carim.
If not, then head through the Fog Gate to face off against the Demon Firesage.
After killing Demon Firesage, progress forward and kill the two Fire Slugs that dart towards you. Then, head down the stairs to get to the next bonfire. Then, head all the way up, killing all the Fire Slugs along the way.
Then, at the top a corpse containing a Soul of Brave Warrior will be guarded by 3 of them. Get this and then head right, up the stairs to activate a lift to Quelaag's Domain. Head back to the bonfire we just discovered.
Head down the branches to encounter the next boss, Centipede Demon. In the right corner of this arena you will be able to get two Green titanite Shards.
Then, head to the left of the arena to encounter Solaire of Astora and a Bonfire. Next, you will be heading to Lost Izalith.