Quelaag is a character from the video game series Dark Souls. She is a powerful boss encountered in the Blighttown area, known for her spider-like appearance and fiery attacks. Quelaag is the sister of Quelaag's Sister, who is a more benevolent character, and both are daughters of the Witch of Izalith. In the game, Quelaag guards the entrance to the Demon Ruins and is a formidable opponent. Players must defeat her to progress further in the game. Her lore is tied to themes of sacrifice and the consequences of the Chaos Flame, which plays a significant role in the game's narrative.