Galva dom Braga, a twenty-year-old daughter of the Duke of Braga, narrates from aboard a ship sailing toward Gallardia, where a third goblin war threatens the human kingdoms of Manreach. Galva has volunteered for the experimental First Lanza of His Majesty's Corvid Knights, an all-female unit paired with war corvids: giant, flightless birds the size of stags bred from ravens by the wizard Fulvir Lightningbinder. The goblins, a subterranean species that regards humans (called kynd) as livestock, have occupied much of Gallardia. The goblin-brewed plague called the Stumbles has killed nearly all horses, stripping Ispanthia of cavalry.
On the voyage, Galva keeps a protective eye on her youngest brother, Amiel, a poet and failed soldier assigned as a supernumerary to Fulvir. Her best friend is Inocenta, a fierce axe-fighter and devotee of Dal-Gaata, the goddess of death, who serves as her
irmana apracera, or non-sexual bedmate. The lanza's commander is Nouva Livias Monçera, a veteran of the previous Threshers' War. A letter from Galva's second brother, Pol, a terce-general, describes catastrophic defeats and the goblins' Hordelaw: In conquered territories, civilians are forbidden weapons, one in nine are sent to manfarms for food, and all receive a crippling cut to a leg tendon at maturity.
The fleet arrives at Espalle, a recently recaptured port bearing marks of occupation: buildings with corners knocked off to destroy symmetry, gibbets displaying the executed. Galva encounters her eldest brother, Migaéd, a sixt-general (an honorary rank for the less capable sons of noble houses), drinking and gambling at midday. Their grandfather's famous springwood shield, the Mouth of the Storm, leans carelessly against a stump. Their father has commanded Migaéd to give it to Galva, but he refuses.
Prima-General Peya Dolón Milat, the Pragmatist, takes command at Espalle, telling the army their individual chances are "frankly terrible" (70) and ordering them to think as a single animal. When a goblin juggernaut attacks the harbor, Fulvir destroys it by summoning a catastrophic storm, with Amiel assisting the ritual. Inocenta invites Galva to a midnight service of Dal-Gaata, where a masked priestess tells the Parable of the King of Wounds, in which a queen kills herself to escape her husband's cruelty and becomes the goddess of death. Galva begins saying the warrior's prayer: "Short life, bloody hand."
The Western Army marches toward the besieged fortress of Carrasque. The corvids grow dangerously hungry, and Galva obtains a military writ granting Nouva authority to commandeer food, making the lanza one of the most hated units in the army. Near Carrasque, the lanza attacks goblin soldiers guarding cage-carts of human prisoners. The corvids spontaneously produce birdscream, a terrifying shriek that forces goblins' protective eye-membranes shut and paralyzes them.
King Luvain of Gallardia hosts a celebration at Carrasque, where Galva first sees Queen Consort Mireya and is transfixed. The king announces the betrothal of his daughter to Migaéd. Mireya tells Galva to call her "Miri," and Galva notices the Eyes of Nerêne, twin violet stars named for the goddess of love, behind Mireya's shoulder, a sign said to mean one will become that person's lover. A fever sweeps the army; Galva nearly dies, nursed by Inocenta.
The combined armies march north and find Goltay, the old Gallardian capital, abandoned and eerily intact. During a skirmish she calls the Battle of the Pigs, Galva freezes in terror, hallucinating Dal-Gaata riding toward her. Inocenta screams at her to say the prayer. Galva screams "Short life, bloody hand!" and the vision breaks; she cuts down goblins before collapsing from a head wound. While recovering, she receives a love sonnet from Mireya. On the appointed evening, Mireya's monkey leads Galva to a covered boat on the river Arve, where they make love.
Amiel drinks a genuine invisibility potion from Fulvir and steals the Mouth of the Storm from Migaéd, who intends to gamble it away. Mireya encounters the apparently flying shield and declares herself Amiel's accomplice. Migaéd retaliates by arriving at the corvid camp with royal chainsmen (guards), demanding the shield. When they seize Galva, her corvid Bellu defends her with restraint, refusing to harm humans. Migaéd orders Bellu killed. The chainsmen execute the bird while Galva is held back. She lays her cheek against Bellu's head, covered in his blood.
Days later comes the Kingsdoom, the massacre of Manreach's assembled rulers. The goblin Horde has tunneled into the Vault of Mysteries beneath the temple of Sath. Ghalls, enormous, pale, drug-addled humans bred underground by goblins, pour into the Field of Flowers. King Luvain and several allied monarchs perish. Nouva leads the lanza to retake the Bridge of Promises; for the first time, ghalls flee from corvids. On the east bank, Segunth-General Samera dom Vinescu, Pol's secret lover, leads a counterattack against orders, and her entire force is massacred.
Outside the walls, Galva learns Amiel is dead, killed trying to deliver the shield to her. She claims the Mouth of the Storm. The Pragmatist implements the Butchered Man, sacrificing rearguard units at successive chokepoints to slow the goblin pursuit. The final lottery falls on Migaéd's battalion at the Horn of Haros, a stone bridge over a deep ravine. After a day and night of fighting, Nouva orders the corvids forward and is killed. Inocenta says "Sister" to Galva for the last time. A ballista fires at Galva, but wind from the Mouth of the Storm deflects the bolt. A dying ghall grabs her belt and drags her into the ravine. Migaéd and his company have already deserted.
Galva wakes on the riverbank. Her surviving corvid, Dalgatha, broke their fall, pulled Galva from the water, and has kept her alive. Mireya arrives and summons a water elemental to heal Galva's injuries. That night, they share a magical dreamspace Mireya has built.
Traveling east, Galva discovers that deserters from Migaéd's command have enslaved refugee women in the hamlet of Roncenay. She kills three men, defeats a mercenary in single combat, and confronts Migaéd, whom she now thinks of as "Not-My-Brother." He flees into a granary. Galva rings the village bell to summon a nearby goblin foraging party, then escapes with Dalgatha, leaving the deserters to their fate.
At the mountain fortress of Durain, Mireya visits on her way north, now married off to the king of Oustrim by her uncle Kalith. She performs a powerful spell, singing to Aevri, a Gunnish goddess of rain and snow. The snows come early, driving the goblins south and saving the army.
Galva returns to Ispanthia to train new corvid knights, eventually commanding 4,000 riders with 7,000 birds that break the Horde and force a peace treaty. King Kalith orders all corvids destroyed, but Galva disobeys and brings Dalgatha to Fulvir, who tattoos the living bird into her skin. The war's aftermath brings betrayal: The Pragmatist, revealed as a high priestess of Dal-Gaata, is scapegoated and falls on her sword. Galva's father coerces Pol into endorsing a lie about the Pragmatist's strategy. Broken, Pol takes his own life.
In the epilogue, Galva returns to the Braga estate and visits Idala, the old blind mare who survived the Stumbles. A castellan summons her to her father. Galva watches the sunset and refuses to hurry. "My father will wait," she says, claiming the independence she has earned from a family whose demands cost her nearly everything she loved.