In the year 2555, more than five centuries after Earth's atmosphere was catastrophically damaged and became inhabitable. Humanity spread across the stars alongside the Rein, Tier, and Grun. The discovery of Solar - the living cosmic energy within all beings - changed civilization forever. Solar powers ships, cities, weapons, medicine, and status itself.
Kileon "Leon" Brand is a thirteen-year-old orphan on a forgotten drifter colony, mocked for having no Solar affinity at all. But on his birthday, a keepsake from his parents unlocks a secret hidden around his neck: Leon was never powerless. His Solar was being suppressed.
When the keepsake awakens, so does an ancient danger connected to Adnal, a fallen Rein warlord who once tried to seize the Solar Keys and bend the universe to his will. Leon is forced into a race across space, into a school for young Solar users, and toward a mystery his parents died trying to solve.
With the help of Seren Vaal, a half-Rein, half-Grun girl rejected by both sides of her bloodline, and Tavin Fenro, a wolf-lineage Tier inventor who would rather build than hunt, Leon must uncover the truth behind the Sun Key before Adnal's followers do.