Smoldering Lake

When you first come into this area, the distant sound of what appears to be some sort of machinery should be immediately evident. And if you were to scan the area above just around the huge tree, you'll see a ballista that will shoot you with three bolts at a time. It will have a short recharge time after every three shots so take that chance to dash off the right, sticking close to the wall and seek shelter in that passageway that you see. This will take you back to the spot where you saw Horace in the Catacombs of Carthus. Turns out he has been corrupted and you'll unfortunately have no choice but to kill him. Grab the Llewellyn Shield off Horace after defeating him. And now you're going to have to tell Anri what happened. Collect the Yellow Bug Pellets and Titanite Shards here too.

There are plenty of other loot back in the first area of this level. However the ballista makes collecting them complicated so it will be best to leave them until later. But there is also an item here that requires assistance from the ballista to get. Look at the section across from the main entrance to this area, and you'll see a wall next to some ruins. Stand near it and evade as soon as the ballista fires; this destroys the wall and reveal a body with a Speckled Stoneplate Ring behind it. Pick that up then turn your attention to the center of the lake. In between a pair of torches is a patch ground made of cobblestones. Bait the ballista to hit this spot and you'll get a shortcut to the bonfire in the Demon Ruins. I'll also be heading through the main entrance to that area later.

Still in the first area, keep out of the ballista's sights and try to make a break for the far door. You will be greeted by a huge sand worm which you must ignore and circle around behind it instead, dodging projectiles from the ballista all the while. Once you are safely in the back, stand by the large chunk of stone next to the sand worm. The ballista will then kill the sand worm when it fires in your direction. Grab the Lightning Stake miracle and the Undead Bone Shard once the worm has died. Also at the spot that the worm once occupied are some remains carrying a Large Titanite Shard and a Shield of Want. Now you have a fork in the road to contend with. The path straight ahead leads directly to the Demon King's chamber, while heading right takes you to the Demon Ruins and also a path that will finally give you the chance to turn off the ballista. There is a Large Titanite Shard in this area too. Head into the ruins and light the bonfire in there next.

This next area is populated with some pretty nasty things including Ghru Pyromancers, Ghru Warriors and a Shaman. Kill off the three Ghru Pyromancers before going for the rest of the enemies. Grab the Ember up top after clearing the area, descend the stairs next to kill a pair of slimes around the corner, and take the Undead Bone Shard off the floor. There are three ways you can proceed from here. The path up leads to an Ember guarded by some Ghru and slime, while the one down lets you kill the ballista. Staying on the main floor where the Ghru Pyromancers were, head right then take a left through the doorway. Follow the path left here, kill the Ghru and hit the wall at the end to proceed. In the larger room beyond is a Black Knight that drops a Black Knight Sword when defeated. Continue along the path into the next couple of rooms, killing off enemies as you see them. In the second room is an Ember tucked away in one of the hallways. Climb the stairs in here to find a bonfire to be lit after killing all the Ghru.

Go into the next room to find another set of diverging paths. Head straight first entering the room cautiously to defeat a couple of Ghru and a Shaman. Grab the Izalith Pyromancy Tome in here and get going. In the main room, move along until you can take a right into a passageway that leads to an area with many corridors. Here take a right at the very first opportunity to enter a room with some rats. Kill them and go hit the wall at the far right corner. Proceed through this new path to score a Quelana Pyromancy Tome from the dead spider at the end. If you take the stairs to the left, you'll end up in a room filled lava with a couple of items floating around, tempting you to take a dip to your death just to get the goods. Well I say go ahead and jump in; but not without some good fire resistant gear. Use those Estus Flasks so you live long enough to grab the items. You are guaranteed to die if you go on this little trip but at least your hands on some loot.

Make your way back to that rat-infested room, go through the door to continue further down only to find more rats. Kill all of them and hit the walls along the left side here until you find a secret passage. Beyond it is a treasure chest containing some Titanite Shards. Hit the wall behind this treasure chest to find a hidden spot you can drop down of to get the Izalith Staff at the bottom. Move down the path to main room past some Basilisks, there is a corridor just before the staircase that you can follow to Knight Slayer Tsorig's lair. Kill the guy to get his stuff along with the My Thanks Emote. Floating in the lava is a Sacred Flame spell to the left and an Ember to the right. Once again getting these things is a one-way trip but worth it. Climb up the stairs, kill the Black Knight on the bridge to grab some free souls before heading up the lengthy ladder.

Once you reach the top, collect the Dragonrider Bow on the right then head back out to the lake where you'll cross paths with the ballista once again. Hide behind the trees and head for the canyon to the left to stay safe. Eliminate the enemies outside the canyon as well as the Skeletons blocking your path to the ballista. Kill them and pull the lever next to the machine to shut it off. Now you can go and safely grab whatever loot you missed out on in this area earlier. Proceed to the boss chamber when you're done and ready.

Boss Battle - Old Demon King

This boss is a fire creature so any defensive gear that's high in fire resist will do great. What we have here is a massive thing with a massive club, so it's fair to expect strong physical attacks from him. As for his fire attacks, most of them have decent range (even the melee ones), so try to get as much distance as you can when avoiding the Demon King's attacks. One thing you can do though is add dark element to your heavy weapon using Human Pine Resin to deal more damage. You'll want to consider equipping a heavier, stronger weapon because power trumps speed in this battle at least for me. The boss is also susceptible to poison so stick that on him if you can. So move in close to attack the legs a couple of times then retreat to be safe. The one chance you have to string combos on this thing, is during his meteor attack which takes a while to cast. Successfully land enough combos to stagger him, which then gives you an even longer window to counterattack.

Defeat this boss to receive some items alongside the Old Demon King trophy. Light the bonfire here and rest before you return to the Catacombs. Once there, go tell Anri what has become of Horace. She will give you the Ring of the Evil Eye. Drop off onto the path below afterwards and follow it all the way to a series of staircases that lead up to the next area, Irythll of the Boreal Valley.