She was described as being tall, with long, straight auburn hair, and eyes that "trapped you like a deer in the headlights."
Agnes' mother Eileen was a member of the Cult of the Lightless Flame. When the Cult decided to create a messiah, a chosen one to usher in the Scoured Earth, Eileen volunteered. She was five months pregnant, and had already taken care of Agnes' father in "the usual manner". Some objected because Agnes had not been "conceived of the flame", but since no one knew how that would even work, they decided it would have to be enough for the child to be born in flames.
The Cult burned down 5 acres of forest to create the site of Agnes' birth. They built a pyre and laid Eileen down on it. As Eileen went into labour, they set her on fire, and when the flames burned down, all that was left was baby Agnes, lying peacefully in the ashes of her mother, untouched.
Agnes' childhood was difficult. She was prone to fits of violent rage, she could not be allowed near other children or left alone for any length of time. She even killed members of the Cult in her temper. Eventually, she settled down and her strength grew. Some member of the Cult believed that Agnes should interact with normal children so Agnes was sent to live at Hill Top Road (MAG 139).
Around 1965, when she was said to be eleven years old, a young Agnes showed up at Raymond Fielding's halfway house on Hill Top Road. She stayed with Raymond for about seven to eight years, up until his disappearance. When questioned on the matter, Agnes said "he had gone away and that the house was hers", and following an investigation that turned up nothing, the house was legally signed over to her. She would continue to stay there for some years up until the house's destruction in 1974 (MAG 8). Agnes was responsible for the destruction of the house, although she remained tied to it after its destruction (MAG 139).
Gertrude Robinson's statements in MAG 145 suggest that sometime during the 1970s she completed a ritual that allowed The Web to bind Gertrude and Agnes together. This ritual was Gertrude's first attempt to stop a ritual by one of the entities, and involved using preserved pieces of Agnes' hair found buried in the ashes of the house at Hill Top Road. At the time, she believed Agnes and the Cult of the Lightless Flame to be "an infernal cult raising their demon messiah to bring about hell on earth." Agnes never referred to Gertrude by name, but called Gertrude her anchor, the thing "weighing her down, tying her to this world and stopping her destiny." In the same statement, Arthur Nolan describes his experience being around Agnes, saying "I saw the sun. So much - power and fire and rage inside of her, enough to burn the world and leave it nothing but desert. But to look at her, oh - It was too much for most. But it seemed so still, so stable. But it wasn’t calm. It was just - distant."
Jack Barnabas visited the Institute to give a statement regarding a short-lived courtship he had had with Agnes during 2006 (MAG 67). In his statement, he explains first meeting Agnes in Canyon Cafe and being immediately drawn to her. Agnes would come into the cafe every Tuesday at 3:00, sit alone with a black coffee, and never drink it. Whenever she left, the untouched coffee remained scalding hot.
Barnabas recalls a man trying to flirt with Agnes once in the cafe. The man began to sweat as he spoke to her, and eventually knocked Agnes's coffee over and onto his own hand; his flesh was immediately burned red despite the coffee having sat for well over the time it should have cooled. There was also a scorch mark on the chair Agnes had been sitting, although Barnabas admits he did not make the connection.
In late 2006, Barnabas sees Agnes talking to an Asian woman with a tattoo of a man wreathed in flames (later revealed to be Jude Perry (MAG 89)). The woman spoke to her about a "job," one Agnes apparently declined. Despite this, the woman handed Agnes an envelope full of what was assumed to be money and left.
A week later, Jack Barnabas asks Agnes out on a date. It was only after she had left that he realizes he hadn't made any plans to meet. Despite that, Agnes shows at his door the next day with no preamble and said they were going to the park. While at his flat, Agnes burns up a spiderweb hanging in the corner.
While on the date, she asks Barnabas if he has a destiny. When he says he does not, she replies with "That must be nice."
During a later date, Agnes suddenly gasps in pain, makes a phone call and mentions "a tree falling" and that they "need to finish something." When Barnabas escorts her home, there is a group of people surrounding her flat. Agnes tells him that she is sorry, and goodbye. Barnabas asks if he can kiss her, and when she takes his face in her hands, his skin immediately starts to burn and blister. It is implied Agnes sheds a tear over harming him.
Barnabas says that, after he wakes in hospital, the police inform him that Agnes is dead and that they have ruled her death a suicide. Her remains were found hanging in her flat, with a hand that was not hers chained to her waist--later confirmed to belong to Raymond Fielding. (MAG 8)
After the disruption of the Great Twisting and Michael Shelley merging with The Distortion, Gertrude becomes aware that her assistant Emma Harvey has been a servant of the Web for some time. Gertrude and Agnes briefly meet in person for the first and only time as Gertrude enlists her help in disposing of Emma, which Agnes allegedly carries out by burning down Emma's home with her inside. The exact date of this meeting is unclear as Agnes died in 2006 and the Great Twisting took place sometime between 2009 and 2011.