The Golden Codex - William Sandberg

At his father’s urging, a teenage boy finds himself working in an antique store while learning arcane skills and knowledge from the owner. While exploring the basement, he unintentionally converts a black coal from the dawn of creation into a mutating manuscript engraved on gold. When a much-feared magus finds out, the boy’s mentor destroys the manuscript and casts it into gold ingots to prevent the magus from accessing the knowledge it contains. But the boy receives a psychic image of the text and becomes a carrier of the golden codex.

The magus, keen to have the knowledge for himself, enslaves the boy in another realm, where he discovers that resistance, even valiantly fought beside a company of champions, is no match for the powerful master. To escape the realm he must enter a deadly contest that promises freedom for the winner and death for the vanquished.