Clary is a young Shadowhunter possessing a unique ability to create new runes. Raised mostly in the human world, she is protective of her loved ones and often rushes headlong into dangerous situations. She searches for a way to awaken her mother from a magically induced sleep while dealing with her complicated feelings for Jace.

Jace is an exceptionally skilled young Shadowhunter. He uses a tough exterior and sarcastic bravado to mask deep insecurities regarding his origins. His rigid adherence to Shadowhunter rules softens as he struggles with his overpowering affection for Clary and the guilt surrounding their presumed shared blood.

Simon is Clary’s mundane best friend who recently transformed into a vampire. Uniquely capable of walking in the sun as a daylighter, he fiercely desires to hold onto his humanity and live a normal life. His loyalty to Clary continually pulls him into dangerous Shadowhunter politics.

Sebastian is a Shadowhunter slightly older than Clary who arrives in Alicante with a tranquil demeanor. Despite his polite exterior, he possesses a formidable combat proficiency and an unsettling aura. He integrates himself into the group's efforts while maintaining hidden motives related to the impending war.

Valentine is a charismatic and ruthlessly ambitious Shadowhunter who views the governing Clave as corrupt. He commands an army of demons and seeks the Mortal Instruments to force the angel Raziel to cleanse the Shadowhunter race according to his bigoted ideology.

Luke is a former Shadowhunter who was turned into a werewolf after a deliberate betrayal by Valentine. Despite facing prejudice from his former people, he is one of the kindest figures in Clary's life. He serves as her primary parental figure and works tirelessly to forge a much-needed alliance between Shadowhunters and downworlders.

Alec is the eldest Lightwood sibling and Jace's parabatai fighting partner. Cautious and rule-abiding, Alec struggles with the homophobic prejudices of Shadowhunter culture, which force him to hide his sexuality. He slowly learns to embrace his authentic self and his feelings for Magnus.

Isabelle is Alec’s younger sister and a fiercely skilled Shadowhunter. Proud of her combat prowess, she relies on careful tactical assessment in battle. She exhibits fierce loyalty to her family but wrestles with guilt regarding the safety of her youngest brother.

Jocelyn is Clary's mother and a former Shadowhunter who fled the magical world to raise her daughter in New York. She placed herself in a magical coma using a powerful potion to prevent Valentine from extracting vital information from her. Her past decisions and secrets drive much of Clary's present journey.

Magnus is the High Warlock of Brooklyn and a powerful downworlder. Confident in his identity, he assists the Shadowhunters with his magic while managing his growing attachment to Alec. He possesses the knowledge required to create the potion that will awaken Jocelyn.

Aline is a young Shadowhunter raised in Idris. Having grown up isolated from the human world, she holds conservative views about downworlders. Her interactions with the New York Shadowhunters slowly broaden her perspective on alliances and identity.

Amatis is Luke’s estranged sister who lives a quiet life in Idris. Having cut ties with her brother after he became a werewolf, she is initially fearful of housing him. Witnessing the bravery of the younger generation slowly helps her reclaim her voice.

Hodge is the former tutor of the New York Institute who betrayed his young charges to Valentine. Living as a pariah in the Shadowhunter community, he holds vital information about the true nature of the Mortal Glass.

Max is the youngest sibling of the Lightwood family. As a Shadowhunter child, he is largely kept out of the main conflicts but remains a beloved and vulnerable member of his family.

The Inquisitor is a high-ranking official who rigidly enforces the Clave's laws. Suspicious of the Lightwood family's loyalties, she uses manipulative tactics to interrogate Simon regarding his unique abilities.

Raphael is the leader of the New York vampire clan. Adhering strictly to traditional vampire laws, he views Simon's ability to walk in the sun as an unnatural abomination.