Nest of Serpents (Wereworld Series #4) by Curtis Jobling

The exhilarating fourth installment in this thrilling epic for middle graders!

The kingdom of Lyssia remains ravaged by war. Drew, the rightful heir to the werelord throne, is locked in battle against Ratlords and Crowlords, when the unexpected return of the evil wereserpent, Vala, throws the war into an entirely new direction. As the battle lines change, so does Drew’s friend Hector, who embraces his powers of dark magistry and transforms into Drew’s most dangerous enemy yet. The Wolf and his allies have never been in graver peril.
 
"Game of Thrones for the tween set." —School LIbrary Journal