Céline was born to Jules and Lisette Montclaire. She grew up in their family's estate in the Provençal countryside of France. Her parents, however, were abusive towards Céline. They would punish her—by locking her in the basement, and beating her—when she made mistakes, and they would train her viciously, leaving her to fend for herself against demons or werewolves to force her to learn. They passed off this abusive behavior as their way of showing their love for her.
When she was eight years old, Céline ran away from home for the first time. She went to Paris and ended up at the Paris Shadow Market, where she felt at home and stayed for two days among the Downworlders, at one point meeting a Silent Brother who bought her a crêpe and offered to take her home, which she refused.
Eventually, however, she was found by the Verlacs of the Paris Institute. She'd begged them to allow her to take asylum at the Institute but was still sent back to her parents who proceeded to torture her. Running away became recurring for Céline as her way of coping. She would sometimes simply go and walk in the forest for days at a time. She also became famous and pitied among the Paris Downworld due to her constantly being spotted wandering around the city.
Hoping to quash her emotions and pain, Céline would have liked to be a Silent Brother had women been allowed. Still feeling like she didn't belong anywhere, she also considered becoming an Iron Sister, but the thought of being stuck in the Adamant Citadel made her feel claustrophobic.
Céline eventually attended the Shadowhunter Academy. Even when she was young, she already admired the Circle, especially Stephen Herondale whom she developed a big crush on, from afar, though her admiration did not go unnoticed by the members. At one point, she became acquainted with Lucian Graymark, the right-hand man of the Circle's leader, Valentine Morgenstern. She was at least once tutored by Luke.
When Valentine offered to let her become a member of the Circle, playing on her desire to be loved and belong somewhere, she accepted, assuming that this was a better option than being in total isolation.
In 1989, Valentine sent the seventeen-year-old Céline, Stephen, and Robert to Paris to investigate the illegal dealings of the warlock Dominique du Froid. When the warlock arrived while Robert was supposed to be going through her things, Céline tried to buy some time. The warlock played along with Céline's questions and sprayed Stephen with a potion that made him blindly infatuated with her and kissed her. Despite knowing it wasn't real, Céline hoped that Stephen also liked her. However, Céline later overheard Stephen telling Robert that he saw her as a child. Hurt, Céline ran away.
While walking around Paris, Céline encountered a woman who, after revealing herself to be a Shadowhunter when Céline saved her from two demons lurking around her, warned her not to trust Valentine. Suspicious, Céline went to Valentine's apartment and eavesdropped on Valentine's conversation with Dominique, realizing that Valentine had made a deal with the warlock to give Robert and Stephen a false testimony about two innocent Shadowhunters. Valentine convinced her to keep his secret, manipulating her by playing on her weaknesses and their apparent similarities and promising that he would be able to give Stephen to her.
Not wanting to lose the Circle, which Valentine made sure to remind her was her only true family, Céline remained silent, even when she found out during the trial that the Shadowhunters that Valentine was framing were her parents. Though she struggled internally for a while, Céline stuck by her choice as long as Valentine kept his end of the bargain.
In a letter Stephen wrote for their son, he stated that, despite not loving Céline the way he loved his first wife, Amatis, Stephen had loved Céline in some way, and Stephen even defended Céline, saying Céline was not responsible for anything that happened. For a time, Stephen also exchanged letters with Amatis, who later passed them onto Jace. While Jace read them, however, he noticed that Stephen rarely—almost never—referred to Céline, causing Jace's antipathy for his father.
At one point, Stephen died during a Circle raid on a vampire's nest. Eight months pregnant with her child, Stephen's death was said to have driven Céline to kill herself by slitting her wrists. Her son was then cut from her corpse by Hodge and taken by Valentine to be raised as his own.
Because Céline's death was said to be a suicide, she was buried at a crossroads in Idris, outside Alicante and near the Brocelind Forest, alongside many others who have been deemed unworthy of having ashes sent to the Silent City.
Céline had been severely abused as a child. The trauma from this led to her having severe self-esteem issues and becoming very trusting of Valentine who manipulated her by relating himself to her. She also had some masochistic tendencies, preferring to be in pain because she believed it made her strong—another remnant of her abusive childhood where her parents would rather her be injured so she could learn from her mistakes than use an iratze to heal her.
Jocelyn once mentioned that it was impossible to hate Céline, that she had a quality about her that made those that knew her want to protect her. Though she was loyal to Valentine, she did not share or understand his hate towards Downworlders.
Céline was said to be blond and very beautiful. Her son Jace is said to look like her around the eyes, though his gold eyes are all his own.
- The Evil We Love (mentioned only)
- The Wicked Ones (first appearance)
- City of Ashes (first mention)
- City of Glass (mentioned only)
- City of Fallen Angels (mentioned only)
- City of Heavenly Fire (mentioned only)
- The Land I Lost (mentioned only)
- Cassandra Clare has stated on Tumblr that Céline did not commit suicide and was actually murdered by Valentine Morgenstern, with the implication that it had actually been Hodge Starkweather himself who did the killing, and that the reason it is not mentioned in the books is because the characters, aside from the two involved, believed that Céline killed herself.
- The Wicked Ones
- An Illustrated History of Notable Shadowhunters & Denizens of Downworld
- The Evil We Love
- A letter from Stephen to his son, a City of Lost Souls Barnes & Noble extra
- City of Ashes
- City of Glass
- City of Fallen Angels
- City of Heavenly Fire
- "... Celine didn't commit suicide. She was murdered." Cassandra Clare on Tumblr
- The implication from Hodge is that he did something terrible to Celine—" Cassie on Tumblr