The Prime Sovereignty, a land divided into five kingdoms, is home to many people of power. Seventeen-year-old Lox is powerful in his own right, although he doesn't fully understand how. All he knows is that - like his mentor, Ember - he has a gift that is both rare and deadly. With his abilities, Lox learns that people like him are born to do only one thing: kill. Just not for free, of course. Thus, with Ember leading the way, Lox begins working in the Prime Sovereignty's oldest, and most fearsome, profession: he becomes an assassin.

However, the practice of assassination - already a complex craft - becomes even more complicated when Lox finds himself tagging along as a member of a team formed by one of the realm's most noble families. A group with members as talented as he is, but far more mysterious, and all tasked to work together in order to achieve the impossible: killing the immortal Emperor Nal.

As he and his companions delve deeper into the secret of the Emperor's immortality, Lox finds himself facing foes more formidable than he ever imagined - enemies fueled by something that dates back to before the existence of the Prime Sovereignty. Tested to his limits, Lox must use his wits, his will, and his blades to secure not just the future of his own realm, but the wider world beyond as well.