NIghtborn (Thrones & Bones #2)

Twelve-year-old Desstra is in training to join the Underhand, the elite agents of the dark elves. But her graduation is jeopardized by the betrayal of a teammate. Things go from bad to worse when she is sent on a secret mission, under the supervision of this same rival. Karn is trading in the city of Bense when he is snatched into the air by a wyvern, who carries him to the home of the dragon Orm. The great dragon tells Karn he believes a second Horn of Osius exists, hidden across the continent in the city of Castlebriar, and that Thianna went searching for the horn and is now missing. With only a dragon’s blessing to aid them and a mysterious riddle to guide them, Karn and Thianna must race the dark elves to a prize that could alter the fate of nations.