Clary is a 15-year-old artist living a seemingly normal life in a New York City brownstone with her mother. She feels out of place and dissatisfied with her appearance, often comparing her freckles and light red hair unfavorably to her mother's striking looks. Her latent ability to see through magical disguises draws her into the hidden world of demon hunters. When her mother disappears, Clary exhibits courage and stubbornness as she searches for answers about her family's concealed past.

Jace is a highly skilled, confident teenage Shadowhunter residing at the New York Institute. Raised entirely within the strict martial culture of demon hunting, he relies on a brash exterior to mask deep-seated insecurities and childhood trauma. His combat expertise and familiarity with runic magic make him a formidable warrior. Despite his arrogant facade, he feels a sudden, protective pull toward Clary.

Simon is a regular human teenager who plays in a band and favors a clean-cut, approachable style. He has harbored a secret crush on Clary for nearly a decade and becomes deeply unsettled when she starts interacting with the dangerous Shadowhunter world. Though out of his element among demons and magic, Simon uses his mundane skills, like archery, to support his friends.

Valentine is a radical, extremist Shadowhunter who led a violent uprising twenty years prior to the story. He believes in purifying the Earth by eradicating all Down-worlders and creating an unquestioning army using the Mortal Cup. Though presumed dead, his ideological legacy continues to terrify the magical community, and his sudden reappearance threatens everyone connected to the Shadow world.

Isabelle is a tall, graceful, and physically strong teenage Shadowhunter who uses a specialized whip in combat. She projects intense self-assurance and embraces her striking beauty as both a personal asset and a weapon. As the only girl in her tight-knit group of demon hunters, she initially views Clary as an unwelcome disruption to her home at the Institute.

Alec is a teenage Shadowhunter who operates primarily as combat support, preferring to protect his team rather than engage in direct, lethal strikes. He struggles with his hidden sexual orientation, a trait frowned upon in his traditional society. His secret romantic feelings for Jace manifest as hostility toward outsiders, particularly Clary, whom he views as a dangerous distraction.

Magnus is an immortal warlock known for his elaborate parties, spiky hair, and glittery aesthetic. As a half-demon, half-human magic user, he operates outside the Clave's strict laws but frequently interacts with Shadowhunters. He possesses unique magical abilities and holds crucial information regarding Clary's missing memories.

Hodge is an academic Shadowhunter confined to the New York Institute by a magical curse. He serves as a tutor and guardian to Jace, Alec, and Isabelle, offering them guidance and historical context regarding the demon-hunting world. His past involvement with extremist factions leaves him physically scarred and conflicted.

Luke is a mild-mannered bookstore owner and a close family friend to the Frays. He has acted as a surrogate father to Clary for her entire life, providing stability and warmth. When supernatural threats surface, Luke adopts a harsh, dismissive persona to push Clary away, though he operates his own hidden network in the city to ensure her safety.

Madam Dorothea is a human psychic who decorates her apartment with stereotypical fortune-telling paraphernalia. Raised by a warlock, she possesses the rare ability to see through magical disguises and actively monitors supernatural activity in her building. She guards a magical, five-dimensional doorway hidden within her home.

Brother Jeremiah is a member of the Silent Brothers, an order of powerful, muted Shadowhunter archivists. He communicates entirely through telepathy and resides in the underground City of Bones. His specialized runic magic allows him to access hidden or blocked memories within the human mind.

Jocelyn is Clary's mother, a tall, thin artist with deep red hair. She has spent the last fifteen years living a quiet, mundane life in New York City, actively hiding her past from her daughter. When her apartment is attacked by a demon, she prioritizes Clary's safety above her own, initiating the events that force her daughter into the magical world.

Raphael is a young-looking boy who initially presents himself as a concerned local trying to keep teenagers away from a dangerous abandoned hotel. He uses this innocent facade to control the perimeter of the vampire lair and dictate terms to intruding Shadowhunters.