I'm trying to fight Quelaag and am having trouble to blocking her AoE, I had my shield (Knight shield) up when it happened and I still lost almost all of my health. I'm also having trouble getting close enough to hit her because she seems to out maneuver my character. Any advice would be appreciated.

P.S. I don't know if it matters but I'm playing as a wanderer

I just kept strafing until she stopped to do a forward facing attack then rushed in some damage. If I remember right the AoE has a tell and when you see it just run out of range.

You shouldn't attempt to block her AOE. Her human torso leans forward a few seconds before she does the AOE so you should get out of the way before she attacks. There is a area where she cannot hit you with melee attacks. If you stand between the spider head and the front leg then she will not be able to hit you with any melee attacks. You'll move away from that safe area when she telegraphs the AOE attack though.

I'm on my first playthrough and just got past this part not too long ago. I ended up just kind of tanking this fight. Blocking the AOE attack and then just healing up the damage, since I had 10 estus flasks to use. Most of her other attacks take a really long time, so you can heal while she does them as long as you're able to survive that one blast.

You could try not locking on and pay attention to the witch's head rather than the spider, so you can see when she's charging up that attack and then just run away. Also when she does that magic sword attack you can just run up against the front of the spider and she shouldn't be able to hit you.

If you can turn to human at the Lower Blighttown bonfire, you will be invaded by Maneater Mildred and she is easy to take out. She will then be summonable right before you go into fight Quelaag. She is a helpful distraction and can do some extra damage as well.

Ditto what the others are saying about hitting her up close until she telegraphs the AOE attack. Also wear your best fire resistance and use the spider shield if you have it so as to reduce any hits from the lava you do take. you should be able to avoid all her attacks as long as you get away from her before she starts spitting lava but you may strafe yourself into a pool of lava if you aren't careful to no corner yourself.

Summon Maneater Mildred and the fight is trivial. Her summon sign is right outside the white light. To get her, you have to be invaded by her by the elevator out of Blighttown (the one leading to the valley of drakes). Good luck

Stay back when she's about to do the AOE. The best time to attack is when she does her extended lava spew.

learn her AoE signs, its pretty easily telegraphed.

Hug right under her sword arm and she'll swing right over you.

Yep, I managed to stick either behind or just infront of Quelaag's legs and wasn't being hit that much, and Mildred kept a lot of aggro for that lava spewing attack.

Personally I always use Flash Sweat when facing any of the fire based bosses. You could also probably switch up your armour for one that has less physical defense and more fire defense. Other than that these guys have said everything else I can think of.

If you need help, there's usually plenty of people to summon by the boss.

Also, this is going to sound weird but the upper part of Quelaag is a woman. That woman "part" of her has no poise so if you hit her she will stagger giving you a few seconds to attack.

Mildred + Sorcery. Mildred will tank her, while you nuke from afar.

Thank you all for the advice, after many lessons on not getting greedy and being patient I finally beat her. I'm now exploring the demon ruins!

When she uses her fire sword you can roll into her to avoid getting hit and also hit her while she is attacking. I killed her using that method. When she starts to bow forward roll away right away to avoid her super AoE attack that does so much damage.

Rolling will be the solution. Stay away from her or learn to roll at the precise moment she does her aoe to do the glitch where it passes through you. Either way, dont get hit by the aoe as its meant to hurt you if your in range no matter what you do to block.

@mrbubbles: CONGRATS! Watch out for the taurus and capra demon(s)!!!