A Forsaken Prophecy by Stacey McEwan

Here is a summary with spoilers for A Forsaken Prophecy by Stacey McEwan

The story begins after the House of Lords attacks Kenton Hill, the stronghold of the Miners Union, a resistance movement made up of non-magical Crafters. The Artisans, who control Belavere Trench, use idium extracted from terranium ore to fuel their elemental magic. Crafters lack access to this magic and are treated as the lower working class. The attack leaves the Union severely weakened, and the Artisans capture Patrick Colson, the last living Alchemist capable of extracting idium from terranium, and Nina Harrow, the first earth Charmer in more than a century. Patrick is furious with Nina because he believes she betrayed the Union by secretly cooperating with the Artisans to save her imprisoned mother, Rose. Nina's former lover, Theo Shop, is also captured. Although Theo is an aristocrat and the son of Lord Terrence Shop, he fought alongside the Union.

The prisoners are taken to Belavere City and brought before Lord Tanner, the Head of the House of Lords. Tanner orders Nina and Theo's Artisan brands removed, draining the idium from their bodies and leaving them without their magic. He also threatens Patrick's imprisoned father, John Colson, beating him severely to force Patrick to produce bluff, a healing substance derived from idium. Patrick eventually complies and saves his father. Meanwhile, Lord Terrence Shop approaches Patrick with a secret plan to overthrow Tanner, whose rule has become increasingly unstable. Shop possesses a book called The Stewards' Testament, which he believes contains directions to Idia's Seam, a legendary source of terranium that could provide an enormous supply of idium. He offers Patrick a deal: help him locate the Seam, and he will negotiate a truce with the Miners Union.

Tanner uses Rose's execution as leverage against Nina, arranging a public execution to force her obedience. Although he intends the threat to pressure Nina rather than actually kill her mother, the executioner pulls the lever, and Rose dies. Nina, devastated by her mother's death, uses a secret vial of idium Patrick had smuggled to her to restore her power. She unleashes her earth magic and buries Tanner alive in the courtyard. Terrence Shop takes advantage of the ensuing chaos, assumes control of the House of Lords, and declares himself the new Head of House. However, Shop reveals that he intends to exploit the same opportunity as Tanner. He offers Patrick a revised agreement in which the Crafter towns will receive a share of the terranium if Patrick helps him locate Idia's Seam. To appease the Artisan ministry, Shop demands that Nina be publicly flogged for killing Tanner. Theo refuses to let this happen and helps Nina, Patrick, and John escape. During their flight, John uses his wood magic to break the axle of Shop's pursuing coach, allowing the group to get away. They head toward Morland, where they hope to find an Artisan capable of translating the Testament's ancient script.

In Morland, the group discovers that the translator they need is Polly Prescott, Nina's former friend and the person responsible for betraying Kenton Hill to the House of Lords. They locate Polly at an Artisan gambling den. When Nina confronts her, Nina's earth magic erupts in an earthquake, drawing the attention of the authorities. Three plainclothes police officers attempt to arrest the group, and Patrick shoots all three to prevent them from stopping their escape. He initially intends to kill Polly as well, but Theo reveals that she is the Scribbler they need. The group takes Polly hostage and brings her to safety. Polly explains that the Testament's script belonged to her grandfather, who believed their family descended from the Stewards, the people associated with the ancient text. She agrees to translate the book in exchange for safe passage out of the continent. Her first translation tells the story of Joan, one of God's three mythical daughters, who was betrayed and killed in Trent. The group interprets the story as a clue to locating the source of terranium.

Patrick, Nina, Theo, John, and Polly travel to Trent through the Miners Union's network of secret tunnels. They discover that the town has been destroyed by the Lords' Army. A survivor named Edith directs them to an ancient oak tree associated with Joan's burial. When the group reaches the tree, an image of a woman appears within its gnarled bark, confirming that the legend is connected to a real place. Before they can investigate further, soldiers attack after a hidden Scribbler alerts the House to their presence. Theo uses his water magic to create a flash flood that devastates the attacking force. During the battle, Theo is shot while protecting Nina. The group escapes, and they continue their search while Theo recovers.

Their next destination is Lavnonshire, where Polly must find a cipher created by her late grandfather to complete the translation of the Testament. The group takes refuge in an antiques shop run by Mrs. Trunk, a mute wood Mason who communicates through a standing piano. Polly learns that her grandfather's cipher was donated to the Geffory Tanner Collection in the local library. She and Theo infiltrate the library to retrieve it and finish translating the book. However, Polly's father betrays them, allowing Lord Shop and his soldiers to capture them. Shop has been tracking the group's progress and reveals that he deliberately allowed Nina and Patrick to escape earlier because he needed them to find Idia's Seam for him. His plan has been to use their abilities and knowledge to uncover the deposit before taking it for himself. Fire Charmers burn Polly's hands to prevent her from writing. Nina causes a structural collapse in the library, enabling Patrick, Nina, and John to escape, but Shop keeps Theo and Polly captive. Before being taken, Polly uses the last of her idium to magically send the Testament's final passage to Patrick. The passage reveals that Idia was buried in the only place where a flower called widow's lace grows: Nina's hometown of Scurry.

Patrick, Nina, and John travel to Scurry to find the deposit. Patrick negotiates with the local miners, led by Nina's estranged uncle, Harland Seymour, known as Kicker, because extracting the terranium will require the cooperation of people who know the area. The miners have previously avoided digging deeper because the ground is unstable and using explosives could destroy the town. Nina's earth magic is essential to reaching the deposit safely. Meanwhile, Patrick's brothers, Gunner and Donny, arrive from Kenton Hill with Theo and a gravely injured Polly, who have escaped from Shop. Patrick is reunited with his family, and his mother, Tess, also arrives with the group. Tess reveals that John murdered Polly's grandfather, Sullivan, two years earlier to steal The Stewards' Testament. John then attempted to sell the book to Lord Tanner and revealed Patrick's identity as the last Alchemist. John insists that he acted to protect his family's future, but Tess shoots and kills him after learning the extent of his betrayal.

The reunion is interrupted when the town's raid siren sounds, warning that the Lords' Army is approaching. The group realizes that Shop knows their location. John had alerted Shop to the Seam in a final attempt to secure an advantage for himself and his family. As the threat closes in, Harland and his miners turn against Nina, capture her, and plan to hand her over to the House in exchange for a reward. Nina is tied to a statue in the town center, near the church where she once prayed with her mother. Faced with another attempt to control and exploit her, Nina unleashes the full extent of her earth magic. She tears the ground apart, creating a massive fissure that splits Scurry in two. The collapse destroys buildings and the church, swallows the terranium Seam, and kills many of Harland's men. The destruction also makes the underground deposit inaccessible and causes further instability throughout the town.

Patrick fights through the collapsing streets to reach Nina and free her. As the ground continues to break apart and underground gas ignites, Nina uses the last of her strength to protect them from the destruction. Patrick gets her away from the ruined town, and they escape with the surviving members of their group. Lord Shop arrives afterward to find Scurry devastated, but he is not left without a means of obtaining idium. Tripp, a young miner from Scurry, reveals that he has consumed idium and developed the ability to act as an Alchemist himself. With Patrick no longer under his control and the original Seam buried beneath the ruins, Shop now has a new Alchemist available to the House of Lords. The House occupies Scurry and prepares to exploit the remaining terranium resources.