Heavenbreaker

The story takes place aboard a massive space Station, one of seven arks built during the Knight's War, an ancient conflict in which a mysterious alien enemy razed Earth. Humanity survived by constructing the Stations and building steeds, giant humanoid mechsuits piloted through a mental link. After the enemy scattered the Stations across the universe, this one orbits a gas giant called Esther in isolation, slowly terraforming it. Society aboard is rigidly stratified: Fifty-one noble Houses serve the Nova-King, while commoners in Low Ward live in squalor.

A prologue introduces three five-year-old children born the same year on the Station. A black-haired girl scavenges food for her sick mother in Low Ward, never having met her father. A platinum-haired boy in a noble mansion is forced crying into a steed cockpit by his mother. A blue-eyed girl in a noble household dreams of knightly honor. Interludes throughout the novel follow a fourth child, a golden-haired orphan raised in the Spider's Hand assassin guild and trained to kill from infancy.

Fifteen years later, the black-haired girl, Synali Emilia Woster, stabs Duke Farris von Hauteclare to death in his office. Synali is the duke's illegitimate daughter, a half-noble, half-commoner bastard whose existence she discovered six months earlier. House Hauteclare sent a Spider's Hand assassin to kill both Synali and her mother to protect the duke's political ambitions. Her mother died; Synali survived with a collarbone scar. After months gathering intelligence in a brothel, she devises a plan to disgrace the House: She will impersonate Mirelle Ashadi-Hauteclare, the legitimate rider, and enter a tournament in the Hauteclare steed, exposing the family's shame.

Disguised in the duke's old riding suit, Synali infiltrates the tourney hall and enters the steed Ghostwinder's saddle, a coffin-sized cylinder filled with pale gel and tiny silver whorls. An electric current links her mind to the machine, and she feels something sentient reaching out; she reaches back, and the mental connection lets her thoughts pilot the steed. Matched against Rax Istra-Velrayd, a brash rider from House Velrayd, the untrained Synali cannot control Ghostwinder. On impact she fractures her skull and wakes two months later in a noble hospital.

A mysterious nobleman named Dravik vel Lithroi has covered up the duke's murder and paid for Synali's treatment. He proposes a contract: For every round Synali wins in the Supernova Cup, the Station's most prestigious tournament held once a decade, Dravik will kill one of the seven Hauteclare family members who conspired to murder her mother. If she wins the Cup, he will dissolve House Hauteclare permanently. His sole demand is that she publicly identify herself as Synali von Hauteclare. Though still longing for death, Synali signs.

Dravik brings Synali to his decaying estate, Moonlight's End, and introduces Heavenbreaker, a dilapidated prototype steed from the Knight's War. During its reboot, Heavenbreaker invades Synali's mind, forcing a vision of hundreds of silver steeds turning toward her. The steed begins speaking in simple words through their link, behavior suggesting true artificial intelligence. Dravik breaks Synali's dominant arm during training to force ambidexterity, a standard technique she mistakes for cruelty. An older rider named Sevrith cu Freynille helps her understand this during a training rescue, and Synali reaches a tentative accord with Dravik.

At the pre-Cup banquet, Dravik reveals he is the former crown prince, son of King Ressinimus and the late Queen Astrix vel Lithroi, who was sentenced for treason. He also reveals he once rode Hellrunner, the king's legendary flagship steed, which is passed down through the royal bloodline as a symbol of their right to rule. Standing before the court, Synali identifies herself as Synali von Hauteclare, names her murdered mother, and warns the seven conspirators that their lives are forfeit. The king invokes an ancient War treaty protecting riders' vendettas, preventing the court from intervening. Pre-War law also makes it illegal to bar any rider with access to a steed from competing, regardless of lineage.

Synali fights her way through the Cup, with Dravik killing a conspirator after each victory. She defeats her first opponent, Yatrice del Solunde of the allied House Solunde, by mentally summoning Heavenbreaker's severed leg through space and using it as a projectile. Her second opponent, Sevrith, wins their bout but deliberately removes his protective handkerchief, a cloth worn over the heart that slows the buildup of nerve fluid in riders' bodies. Without it, he collapses into overload, an irreversible coma, handing Synali the win. From Rax, Synali learns every saddle's gel is derived from the enemy's nerve fluid, which accumulates in riders with each match. She commissions Jeria, a hacker from the brothel, to infiltrate Dravik's vis, his personal holographic device, and discovers brain scans showing pockets of nerve fluid spreading through her own brain.

In later rounds, Synali defeats Olric von Westriani, an aggressive rider from House Westriani, by calling Heavenbreaker back after its hull is breached in vacuum, and survives a bout against a convicted killer sent to assassinate her. She faces Crown Princess Leyda, Dravik's half-sister, who weaponizes the flash of white light between steeds on impact, revealing it as the enemy's natural weapon. Dravik takes Synali to a charnel tower, revealing that commoner corpses are stripped of their heads and sent beneath the Station's artificial ocean. Her relationship with Rax deepens; she kisses him once, then pulls away. She discovers that Luna, a gold robot-dog at Dravik's manse, houses a true AI built by Astrix that transmits into Heavenbreaker, explaining the steed's sentience and self-repair.

Through Leyda and Dravik, Synali learns the enemy is not dead: When injured, the aliens revert to nerve fluid and try to regrow by consuming memories, producing energy in the process. The Station's main reactor, called the core, is a massive tube of nerve fluid beneath the ocean, fed with the severed heads of Low Ward's dead. Queen Astrix was sentenced for treason because she believed enslaving a sentient species as a power source was wrong. The king forced her to choose between execution and overload; she chose to overload in Heavenbreaker, where her consciousness persists.

The climactic seventh match pits Synali against Mirelle, whose family has secretly disabled safety protocols on their steed so that impact floods the opposing rider with unfiltered nerve fluid. On collision, silver fills Synali's eyes and she loses consciousness. Inside the overload, she encounters thousands of past riders preserved within the nerve fluid and relives Astrix's memories. She also recovers a suppressed memory: After the assassin killed her mother, young Synali grabbed his dagger and stabbed herself in the collarbone, trying to die. The assassin, whose ice-blue eyes matched hers, stopped the blade and whispered, "You must live." In the deepest layer, Heavenbreaker manifests with Synali's face. They embrace and fuse into one consciousness.

Synali becomes the first rider in history to recover from overload, returning with one blue eye and one silver eye. She defeats Mirelle with a helmet hit, but the king's guards arrest her and transport her to the core laboratory. The novel's interludes reveal that Rain, the golden-haired assassin, is Synali's half-brother, another of the duke's bastard children. After Rain's guild brother Green-One betrays him to the king, Dravik finds Rain and offers him a choice: die or help rescue Synali. Dravik also imprisons Rax and reveals his full plan. Astrix's goal was to grow a second living enemy inside Heavenbreaker to challenge the one in the king's steed Hellrunner, collapsing the core's forced obedience and freeing the enslaved aliens. The book ends with Synali in the laboratory, one eye blue and one eye silver, the core screaming beneath her feet, as the narrative announces it will continue in Hellrunner.