Also known as the Darkmoon Knightess, the Lady of the Darkling can be found at the first bonfire in Anor Londo. She is the bonfire's Firekeeper, tasked with keep it lit. Like the other Firekeepers, offering her a Firekeeper's Soul will allow the player to reinforce their Estus Flask another level.
As a memember of the Blade of the Darkmoon and an ally of Dark Sun Gwyndolin, she wears the Brass Set armor. This armor aides her in hunting down those listed in the Book of the Guilty and serves to hide her hideous appearance.
The Lady of the Darkling will become hostile to the player if the illusion of Gwynevere is destroyed, if Gywndolyn is killed, or if the player trespasses in the Darkmoon Tomb without wearing the Dark Moon Seance Ring. Should the player kill her, she will drop a Firekeeper Soul of her own which can be taken to one of the other Firekeepers in the game to further reinforce the Estus Flask.
Should the player join the Blade of the Darkmoon covenant, the Lady of the Darkling can still be killed for her Firekeeper Soul without breaking allegiance to the covenant.