Series information from Goodreads.com.

"The Queen's Assassin is forced to take on a mysterious apprentice on his most dangerous mission yet, pulling them both into a vicious web of secrets and lies"--,Provided by publisher.

Caledon Holt is the Kingdom of Renovia's deadliest weapon, the Queen's one and only assassin. He's also bound to the Queen by an impossible vow: to find the missing Deian Scrolls, the fount of all magical history and knowledge, stolen years ago by a sect called the Aphrasians. Shadow has been training all her life to become skilled enough to join the ranks of the Guild. Magic has been forbidden since the Aphrasian uprising, so Shadow has been learning to control her powers, hoping that one day she'll become an assassin as feared and revered as Caledon Holt. Forced to team up as assassin and apprentice to hunt down a new sinister threat to Renovia, Cal and Shadow uncover a shocking web of lies and secrets that may destroy everything they hold dear. -- adapted from jacket