A half-woman, half-spider demon located in a small lair near the bottom of Blighttown.
One of the Witch of Izalith's daughters, transformed into a monster by the flames of chaos. She guards the second Bell of Awakening.
Black Knight Shield, or some other high fire resist shield, and fire resistance/physical resistance armor as this helps stop much of the damage from her fire AoE attack. The Flash Sweat pyromancy is also extremely helpful both against her direct attacks and in case you get knocked into her lava pools, although you may need to re-apply it during the fight. Like most bosses, Queelag has a tendency to immediately target the host as the first person through the boss gate, so summons should do their best to charge her or otherwise quickly land an opening attack (even something as minor as a thrown dagger), which will almost always distract her away from the host. Failure to do so can result in a quick charge or leap attack on the host, often pinning the host near the entrance and leaving them unable to avoid her devastating Fire Wave attack.
It is generally easier to focus on attacking her legs rather than her body, as this allows you to retreat more quickly and also avoid getting trapped between her legs and her body when she starts turning or jumps. It is also possible to dodge all three of her sword attacks if you time it right. Just make sure to dodge to your right for the first two attacks, otherwise they'll both hit you. Simply walk forward and to the right to avoid the thrust attack; you can take advantage of that moment to clobber her with a strong attack. Typically she'll jump back after that; if she doesn't, there's a good chance she's about to use her Fire Wave attack, so back up quickly and block (which will absorb some of the damage if you don't get clear far enough).
Another relatively easy way to win is equip a bow, and as soon as the fight starts run to the stairs that Quelaag comes down from. To the left of them is a small walkway that goes up; stand in there and shoot her to death making sure to shoot her human half. It is possible that she may still use the AoE blast or spit lava at you, but generally she cannot reach you if you keep staggering her with arrows.
Other things to note include that making her spit lava pools near the sides of the room drastically gives melee players more space in the middle of the room, making it easier to avoid her AoE attacks and block/dodge. Also, if the area you're fighting in is getting a little crowded with lava, un-target and run off to a clear area. Just be careful that she doesn't use the Lava Rush attack while getting close to you.
- Weak Against Electric
- Immune to Fire (notably Pyromancies)
- Arrows or other projectiles (such as throwing daggers) to the female body make Quelaag stagger
- Fire Slashes: She slashes either left to right or right to left with her sword. Block or roll to avoid these. These slashes are also angled outwards from her human portion and therefore typically miss if you are very close to the spider's head. Not a huge threat.
- Fire Stab: This attack extends straight forward over the spider's head and has much more range than might be expected. It usually follows her two close range fire slash attacks, but occasionally will be used by itself. If you are in front of her when she starts winding up for it, either roll backwards or to the side several times, or if you are close enough, simply walk forward and to the right. The initial stab can also be mostly deflected if you are blocking with a high fire resistance shield, but you will still want to get out of the way of the attack as soon as possible. Can be a significant threat.
- Lava Breath: When she pats the spider's head or the spider looks like he is going to vomit she will use this attack. She will spit lava on the ground in an arc around her, leaving pools of molten magma that stagger you and set you on fire, making it difficult to escape the lava once you are trapped in it. Alternatively, if you are far enough away she may shoot 4-5 balls of lava at you. The animation on this attack can be deceptive, as the actual lava pools often appear farther out from her than where it appeared she was spraying them. These attacks are slow to execute and provide a good opportunity to strafe around to her side and land several melee attacks.
- Lava Rush: If she pauses while still some distance from you, watch out and back up! The spider will leap towards you, spitting lava simultaneously. It's very easy to get knocked back into the lava it spits with this attack if you don't back up far enough. Trying to dodge to the sides is very difficult to do successfully. A better tactic can be to immediately start strafing to one side while she is in midair, as she cannot correct her flightpath once airborne. With a little practice, you should end up beside her and behind her lava spray, giving you another opportunity to land some hits.
- Stomp: She pauses and stomps on one side or the other with her spider legs, causing small damage that is easily dodged or blocked by a shield. The only thing to watch out for is not letting her legs strike you on the head from above, as this can circumvent your shield to knock you down and do more damage.
- Fire Spray: On rare occasions, the spider's large abdomen will start to shake and she will spray small clouds of reddish purple energy around and behind herself in a rough cone shape, similar to but different from her fire wave attack. Usually occurs when repeatedly attacking her abdomen directly from behind, while a phantom keeps her attention. Given the rarity of this attack and the fact that anyone behind her in the primary danger zone will not see the windup for it, it can be a real surprise to anyone running up behind her. It must be blocked or dodged at the risk of very serious damage.
- Fire Wave: Her most dangerous attack. Whenever she bends forward and reaches down the sides of the spider's head with her arms she is preparing her large 360 degree AoE attack. Back up immediately while keeping your shield toward her, as this attack has a surprisingly large range, and can either kill players outright or severely wound them and then knock them into nearby lava pools. Melee combatants should get in the habit of attacking her legs rather than her head or body, to give themselves that much more of a cushion of space to escape her fire wave attack when retreating. She has also been known to spam this attack 2-3 times in a row, which is particularly dangerous if you are close to a wall or otherwise unable to retreat. Major threat!
Player summons from the nearby bonfire at the bottom of Blighttown can also make this fight easier than even a typical multiplayer boss fight. Quelaag's AI can be unstable when she has multiple foes to choose from, and she often abandons pursuit of one target when another injures her (also allowing players to rescue one another if one gets trapped by her). Given her fairly slow turn speed and the long windup of most of her attacks, it is easy to trap her in her own aggro cycle by having one player attack her a few times and then retreat so that another player may then attack her from her rear or sides, usually causing her to try to turn around and go after the latest attacker, which then leaves her open to other attacks by the initial attacker and so on. This is particularly effective if one or more foes is using ranged spells or miracles such as lightning spears, as multiple close melee attackers remain vulnerable to her powerful fire wave attack, which has a 360 degree area of effect and a large radius. By effectively resetting Quelaag's focus by having other players hurt her whenever she starts concentrating on a particular player, it is not uncommon to kill her without anyone taking any damage. One side effect of this tactic is that Quelaag may get so rattled that she ends up boxing herself in with lava spits in a circle around her. Melee characters should consider bringing a ranged weapon such as a bow or throwing daggers to help maintain aggro on her while waiting for the lava moat to start disappearing.