Kamzin has always dreamed of becoming one of the emperor’s royal explorers, the elite climbers tasked with mapping the wintry, mountainous Empire and spying on its enemies. She knows she could be the best in the world, if only someone would give her a chance. But everything changes when the mysterious and eccentric River Shara, the greatest explorer ever known, arrives in her village and demands to hire Kamzin—not her older sister, Lusha, as everyone had expected—for his next expedition. This is Kamzin’s chance to prove herself—even though River’s mission to retrieve a rare talisman for the emperor means climbing Raksha, the tallest and deadliest mountain in the Aryas. Then, Lusha sets off on her own mission to Raksha with a rival explorer, and Kamzin must decide what’s most important to her: protecting her sister from the countless perils of the climb or beating her to the summit. The challenges of climbing Raksha are unlike anything Kamzin expected—or prepared for—with avalanches, ice chasms, ghosts, and other dangers at every turn. And as dark secrets are revealed, Kamzin must unravel the truth about their mission and her companions—while surviving the deadliest climb she has ever faced.

After the terrifying events on Mount Raksha, the witches have returned, and River has betrayed Kamzin to regain his dark powers. The witches’ next step: march on the Three Cities and take over the Empire—led by River’s brother, Esha. If Kamzin is to save Azmiri and prevent the fall of the Empire, she must find a star that fell in the Ash Mountains to the north. Fallen stars have immense power, and if Kamzin and Lusha can find the star, they can use its magic to protect the Empire. To get there, Kamzin has allied with Azar-at, the dangerous and deceptive fire demon, who can grant her great power—in exchange for pieces of her soul. But River wants the star too, and as their paths collide in dangerous and unexpected ways, Kamzin must wrestle with both her guilt and her conflicted feelings for the person who betrayed her. Facing dark magic, a perilous journey, and a standoff against the witches, can Kamzin, Lusha, and Tem find the star and save their Empire?