Half City by Kate Golden

Here is a summary with spoilers for Half City by Kate Golden

Viv Abbot lives in Astera, a city divided by the massive Chasm that separates the wealthy northern part of the city from the poorer Babylon neighborhood to the south. Viv works at the Windsor Museum and maintains a normal-looking life with her best friend and roommate Penny, her boyfriend James, and her family. However, Viv has secretly been hunting supernatural creatures called deviants since childhood. Her father taught her to hunt before he was murdered by members of the Brood, a powerful group of demons. Viv is an aeon, an extremely rare type of hunter who can sense deviants before they reveal themselves and develops hunting abilities much earlier than normal hunters. Aeons were believed to have been hunted to extinction because they possess an uncontrollable bloodlust toward deviants. Viv has spent her life hiding this part of herself because she is afraid that her instincts make her a monster, and she truly believes she is the only one left.

Viv encounters a demon on the subway who is stalking a mother and her children. She attacks him and kills him, but afterward realizes that another demon has been watching her. That demon follows her into Babylon and introduces himself as Reid Graveheart. Reid is a member of the Brood, the same organization responsible for her father's death, but instead of attacking her, he tells her that he is an instructor at Harker Academy for Deviant Defense, a secret school for hunters. He gives Viv an ancient lymantrian coin and tells her to insert it into a broken ticket machine in a utility closet at the Windsor Museum. Viv initially assumes the offer is a trap, but after finding an old silver locket among her father's belongings bearing the words "Harker Bound," she realizes that Reid was telling the truth. Her father had attended Harker under a different name. Viv uses the coin and is transported to the academy.

At Harker, Viv discovers that her father attended the school under the name David Cadell rather than David Abbot. She also learns that he had an entire life there that she knew nothing about. Harker is a hidden college where young hunters study supernatural creatures, combat, magic, and the history of the deviant world. Viv meets Kitty Briggs, Peter Roydon, Sophia Valentine, and Elliot Thompson. Sophia becomes her roommate, Peter is extremely knowledgeable about supernatural history, Elliot is a physically powerful athlete, and Kitty is competitive and serious. Viv quickly becomes part of the group, although she continues hiding the fact that she is an aeon. She also continues to clash with Reid, who teaches combat and repeatedly criticizes her tendency to act before thinking. Reid initially refuses to allow Viv into his advanced Field Training class because he considers her too reckless.

The first major threat appears when wraiths attack the Harker dormitories. The creatures tear through the building and seriously injure students. Afterward, Kitty is apparently missing, and a note is found suggesting that she voluntarily left Harker. Peter does not believe the explanation because the handwriting and circumstances do not make sense. Around the same period, a supernatural attack occurs during a lacrosse event involving zombies, and an Aeon's Dagger is stolen from the Harker armory. The dagger is particularly important because it is one of the weapons associated with the rare aeon hunters, and it appears that someone used Kitty's name to gain access to it. Viv begins to suspect that the attacks, the missing student, and the stolen dagger are connected.

Viv, Peter, Sophia, and Elliot eventually break into the restricted Harker archives using a key card Viv steals from Reid. There they find information about an ancient dark spell called a syrabraxa. The spell is connected to the creation of the Chasm and is capable of producing enormous destructive power. The ingredients include the liquefied blade of an Aeon's Dagger, an asphodel flower from a hidden Harker garden, the eye of a conjuring witch, and the blood or essence of an aeon. The discovery makes Viv realize that whoever is collecting the ingredients may be looking for her. She eventually tells Peter, Sophia, and Elliot that she is an aeon. Instead of being afraid of her, they accept her immediately. Sophia admits that she had already suspected the truth, Peter calls Viv family, and Elliot promises to protect her. Viv finally has a group of people who know what she really is and do not consider her a monster.

Viv and Reid become increasingly involved with each other while investigating the conspiracy. During Field Training, the students encounter a strzyga, a dangerous spider-like deviant attacking people in the city. Viv ignores Reid's order to retreat and follows the creature into an Italian restaurant. Reid follows her, and during the fight he reveals his true demonic form, including red scales and black claws. Viv and Reid work together to kill the strzyga by setting spilled alcohol on fire, causing the restaurant to explode. Reid carries Viv out of the burning building, and both are injured. Afterward, Viv tells him about the syrabraxa investigation. Reid agrees to help investigate the missing students and locate the hidden garden where the asphodel grows. Their relationship changes significantly after fighting together because Viv begins to see Reid as someone who protects people rather than simply as one of the demons she has been taught to hate.

Viv's ordinary relationship with James deteriorates at the same time. James is part of the wealthy northern side of Astera and does not understand or appreciate Viv's hunting life. On Halloween, Viv wears a red devil costume, partly because Reid previously told her she would look good in red. While out with her friends, she finally breaks up with James. James reacts angrily and reveals that Viv's mother has apparently told him that he could do better than Viv. Afterward, Reid finds Viv outside the bar and comforts her. They joke together about the breakup, and their relationship becomes openly romantic. Viv is increasingly drawn to Reid because he understands the parts of her life that everyone else has rejected.

After a sparring session, Reid accidentally cuts Viv's arm with his claws. She goes to his cottage because she cannot properly stitch the wound herself. Reid treats the injury and finally tells Viv more about his past. He was raised by a brutal demon father and brother and was part of the Brood before eventually turning against them. He explains that his older brother killed the woman Reid loved. Reid also reveals that the Brood had originally sent him to Harker to kill Dean Edgar Driscoll, but Driscoll instead offered Reid a place at the academy. Reid has spent much of his life hating his own demonic nature because he does not want to consume souls. Viv recognizes the similarities between Reid's self-loathing and her own fear of her aeon instincts. She asks him to kiss her, and he does. Their relationship becomes physical after that, although Reid repeatedly struggles with the fact that, as a demon, he is capable of taking Viv's soul.

Viv and Reid continue searching for the missing ingredient for the syrabraxa. Professor Lisette tells Viv that asphodels grow in high places, leading Viv to suspect the abandoned planetarium at Harker. Reid joins her there, and he gives her an enchanted bracelet called a lure that will alert him if she is in danger. They pretend to be ordinary people on a first date, with Viv playing a photographer and Reid playing a planetarium expert. During their game, they activate the planetarium's projector and accidentally discover a hidden room. Inside is a garden containing glowing white asphodels. Several of the flowers have already been removed, proving that someone has been collecting the ingredients for the syrabraxa. They also find a bag of poppy dust marked with a white antler symbol. Shortly afterward, they learn that another Harker student, Lyra Roth, has disappeared.

Viv connects the white antler symbol to Fever Dream, a nightclub in the Chasm's underground area. Both Kitty and Lyra had connections to the club. Reid tells Viv to stay away because the club is controlled by the White Stag, a powerful and dangerous demon crime lord. Viv ignores him and goes to Fever Dream with Sophia and Penny. She gives Penny the magical lure bracelet before entering because she wants it to protect her friend. Inside the club, Viv encounters vampires, werewolves, and other deviants before following a suspicious person into a private office. There she meets the White Stag, a powerful demon named Deacon. Viv attacks him because she believes he is responsible for the missing students, but Deacon easily overpowers her and nearly takes her soul. Reid arrives before Deacon can kill her. During the confrontation, Viv discovers that Deacon is Reid's older brother. Reid had previously allowed Viv to believe that his brother was dead.

The revelation destroys much of Viv's trust in Reid. Penny and Sophia are also outside the office, and Penny sees Viv being carried out injured. Sophia accidentally reveals that Viv and Reid are romantically involved, which causes Penny to realize how much Viv has been hiding from her. Penny is devastated that Viv has kept so many secrets. Viv and Reid argue afterward, with Viv accusing him of lying about Deacon and Reid accusing Viv of constantly putting herself in danger and sabotaging their relationship. Viv ends the relationship. The fallout continues when Viv learns that she has missed the opening of the Windsor Museum's major Chasm exhibit and is fired by Fiona. Her relationship with her mother also deteriorates further.

A week later, Viv is still dealing with the aftermath. She studies with Peter, and the two discuss their experiences with losing their parents to demons. Viv then returns to the Windsor Museum to collect her belongings and confronts her mother. Viv accuses her mother of hating her and blames her for treating her coldly for years. Her mother finally admits that her husband's death devastated her and that her grief made it difficult for her to show love to Viv. Before their conversation can go further, the museum's security alarms sound. Viv senses deviants inside the building.

The Brood has invaded the Windsor Museum. Viv discovers that the demons are searching the Chasm exhibit for a specific artifact. The High Thane, the leader of the Brood, is present but escapes through a magical gateway with another warlock. Viv and Reid fight the remaining demons. During the battle, a woman wielding a silver spear saves Viv. The woman reveals herself to be Fiona, Viv's sister-in-law and former boss at the museum. Fiona's true identity is Gemeline Lisette, the Harker professor Viv has known as Professor Lisette. Fiona is a dichotomous shifter who can exist in two different forms and has secretly been living both lives. She admits that she knew Viv was a hunter and deliberately hired her at the museum so she could watch over her and eventually help her reach Harker.

Fiona explains that the artifact the Brood stole is a gnostic censer. The censer is important because it protects the person casting a syrabraxa from the madness caused by the spell. The timing is now critical because the next new moon is approaching, and Fiona realizes that the High Thane intends to complete the spell very soon. She leaves to contact the Citadel while Viv and Reid remain at the museum. After the battle, Reid admits that he realized he was falling in love with Viv during their fight against the strzyga. Viv realizes she feels the same way but cannot bring herself to say it, so she kisses him instead. They have sex on the museum floor. During the encounter, Reid's demonic nature becomes even more apparent: when his emotions and desire intensify, large curled horns emerge from his head. He admits that he really does desire Viv's soul and has to constantly fight the instinct to take it. Viv does not reject him and instead accepts his horns and his demonic nature.

The following morning, Viv has a vivid memory of the night her father died. She remembers being hidden inside a shipping container at the docks while Brood demons attacked him. Her father recognized one of the attackers and eventually threw himself from the docks rather than allow the demons to consume his soul. Fiona then tells Viv that her father's autopsy report contained a strange detail: he had carved the number 26 into his own hand before he died. Viv remembers a photograph at Harker showing her father on a lacrosse team and notices that the player wearing number 26 was Edgar Driscoll. She realizes that Dean Driscoll was not simply an administrator who knew her father. He was directly connected to him.

Viv, Reid, and Fiona return to Harker and examine the old photograph. Viv confirms that Driscoll was the person associated with the number 26. She realizes that Driscoll is the person who killed her father and has been working with the Brood. Driscoll had been using his position as dean to manipulate Harker's students and access the resources necessary to create the syrabraxa. Kitty and Lyra were not random victims. They were kidnapped because Driscoll was searching for an aeon capable of serving as the spell's host. The missing students, the stolen dagger, the asphodels, and the other supernatural attacks were all pieces of Driscoll's plan.

Viv and Reid attempt to reach the Citadel, but Viv suddenly hears Penny screaming through the lure bracelet. Penny has been kidnapped and taken to the docks. Viv and Reid abandon their original plan and race there. Reid attacks the Brood demons guarding the area while Viv finds Penny inside a shipping container. Viv realizes that the container is part of a trap. She frees Penny but understands that the kidnappers are expecting Viv to be the person inside. Penny helps Viv disguise herself as the captive by tying her up and hiding. The Brood demons return, take Viv from the container, and carry her into the warehouse, believing they have captured the person they wanted.

Inside the warehouse, Driscoll reveals that he knows exactly who Viv is. He tells her that she is David Cadell's daughter and the last aeon he has been searching for. Driscoll admits that he killed Viv's father. His motivation was partly jealousy and resentment toward David, and he had spent years pursuing aeons because of their unique power. The High Thane's son, Finn, is also present. Viv finally understands the real purpose of the syrabraxa: an aeon is required as a living host for the spell. The host can contain the magic, allowing the High Thane to eventually use the power to break open the Chasm and unleash the demons and deviants trapped beyond it into the human world.

Driscoll performs the ritual and pours the syrabraxa onto Viv's back. The magic burns through her clothing and into her body, fusing itself to her soul and spine. Viv becomes the living host for the most powerful dark magic in the world. The spell is successfully completed, leaving Viv physically injured and permanently connected to the magic. The High Thane's plan is to kill her afterward and use the power contained within her to tear open the Chasm.

Reid arrives at the warehouse badly injured and attacks the Brood demons, creating an opportunity for Viv to escape. Viv finds Driscoll near Penny and realizes that he is about to kill her. Viv fights him and manages to stab him. Driscoll warns her that killing him will leave her trapped with the syrabraxa because only the person who cast the spell can remove it. Viv understands that he may be the only person capable of freeing her from the magic, but she chooses to kill him anyway because he murdered her father and is responsible for everything that has happened. She delivers the final blow, killing Driscoll. As he dies, he attempts to warn her about Reid, saying, "Reid. He's...he's not," but he dies before completing the statement.

Viv gets Penny to safety and gives her a cover story to tell the police so that Penny will not have to reveal anything about the supernatural world. Viv is badly injured and realizes that she has nowhere safe to go. Reid is missing after the battle, and she does not know whether he survived or was captured. She is also now carrying the syrabraxa inside her body, making her the target of the High Thane and the Brood. Rather than return to Harker or the museum, Viv goes to Fever Dream because she has no other option. She approaches Deacon, the demon who nearly killed her earlier and the brother of the man she loves, and tells him that she needs help. When Deacon sees the magical wound on her back and realizes that the problem concerns Reid, he stops himself from killing her and brings her inside the club.