Centipede Demon is a boss you'll encounter as you explore the Demon Ruins in Dark Souls.
Centipede Demon boss strategy
Centipede Demon is one nasty bugger. It comes very quickly after the last boss fight, and is much more relentless, simply due to the arena that you're going to fight it in. There is a lot of Lava here, which is going to be more of a dangerous enemy than the boss itself. Try to stay on the ground here- and summoning Solaire of Astora here is a great idea, as he cannot be damaged by the Lava.
There are a few key points here that you're going to want to know. Firstly, for the love of god do not use a Fire Weapon, Chaos Weapon or Pyromancies. The Centipede Demon is fully immune to it and it will not do any damage whatsoever.
If you do not have a weapon that is any of those, we would recommend upgrading a weapon to +14 and enchanting it further with Great Magic Weapon or Crystal Magic Weapon for an extra damage boost.
Secondly, you can actually sever the tail of the Centipede Demon and make this fight a lot easier. As difficult as it sounds, try to target the tail in the initial stages of the fight with a bow, or melee attacks in order to sever it and get the Orange Charred Ring, this will then allow you to traverse through the lava unscathed. It does not take too much to sever the tail, and we recommend doing this as quickly as possible.
If you have ranged Sorceries, this is the time to use them Soul Arrows and Homing Soul Arrows are incredibly potent, and dish out a whole lot of damage, to boot.
If you are playing melee, we would recommend that you head towards the right, which is significantly less covered in lava than the rest of the arena. From here, you will be able to dodge it's arm attacks pretty handily to get close and do some serious damage. Again, if you can roll towards the tail, do so.
When up close, beware of the Centipede Demon's attack which can also grab you, in addition to the jumping attack which will break your lock-on. You should have enough time to roll out of the way and towards safety. Your biggest window is going to be when the Centipede Demon attacks with its arms.
When the boss is at low health, it will begin to do a homing fireball attack which is incredibly potent in addition to being hard to dodge. The Centipede Demon will usually cast this when you run away to heal.
In addition to this, the jump attack also gains an explosion, which can quickly set you in the lava. We recommend carrying a Divine Blessing or Hard Humanity around to fully restore your health if you get hit, as it will fully restore your health.
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 you need larger windows to defeat this boss, we definitely recommend summoning in Solaire, in addition to doing a lot of damage, he will also be able to eat a lot of the Centipede Demon's attacks for you, meaning that you should be able to handle it and dish out loads of damage no problem.
The only problem with this, is that the fight can easily be drawn out into the Lava away from you, so just aggro the Centipede Demon back in order to draw the attention back on yourself. Then, you should be able to draw it back onto land and attack it from there and let Solaire get most of the heat.
This fight is tough, but the main thing is to ensure you have as many healing items as you can on hand to restore your health if you get caught in the lava. After this, you will be able to proceed to Lost Izalith, where one of the Lord Souls lies.