Ivy Langston has spent her life reading the language of mountains.A practical naturalist and skilled forager, she trusts maps, seasons, plants, and the instincts passed down to her by her grandfather. But one spring morning at Black Tarn, the laws of nature break apart before her eyes.A magnificent white stallion runs across the surface of the bottomless lake, freezing the water beneath every hoof. Then, without slowing, he leaps into the sky and climbs the clouds as though they were stone stairs.Ivy soon discovers that the creature is no ordinary horse.Beyond the mortal mountains lies Aethelvale, a hidden kingdom caught between the seasons and slowly being erased from existence. Its people are fading into mist, its landscapes are disappearing at the borders, and reality itself is beginning to unravel. The kingdom's rulers have spent centuries trying to control the celestial stallion, believing his power could save them.But they have misunderstood him.The white horse is actually Prince Tristan Everhart, a lost sovereign cursed to exist inside the body of an untamed celestial creature. His empty throne and imprisoned soul are bound to the fate of the kingdom.Ivy becomes the first mortal to understand what generations of kings and hunters could not: Tristan cannot be saved through possession. No saddle, bridle, chain, or iron bit can restore him. Freedom is not an obstacle to the kingdom's salvation-it is the key.But the realm is collapsing faster than anyone expected.The Erasure has reached the edges of Aethelvale, consuming mountains, rivers, buildings, and living beings. The remaining guardians reveal that Ivy carries the blood of the ancient Founders, giving her the temporal strength necessary to survive the impossible passage ahead. Tristan is the thread; Ivy is the anchor. Together, they may be able to cross the Seasonal Meridian and repair the fractures tearing the hidden kingdom apart.With the kingdom disappearing behind them, Ivy climbs onto Tristan's bare back-not as a master claiming a mount, but as a companion placing her life in the hands of another free soul.Their final journey takes them into the heart of the Seasonal Horizon, where Spring, Summer, Autumn, and Winter collide in a catastrophic storm. If Tristan loses his stride, they will fall into the void. If Ivy loses her connection to the mortal world, both horse and rider will be erased.Their only weapon is trust.Their only path forward is to run.And at the impossible center of the storm, Ivy and Tristan discover that the world was never meant to be conquered or controlled. It was meant to remain in balance.Together, they may become the first riders to cross the boundary between seasons-and the last hope of a kingdom that has forgotten how to survive.
