Wingfeather Saga: The monster in the hollows

Janner Wingfeather, elder son of the High King of Anniera, is forced to flee the kingdom with the rest of the royal family in the absence of his father, while the Fang armies of Gnag the Nameless are in hot pursuit, but when they reach their last safe haven, the Green Hollows--home to warriors feared by the Fang of Dang--Janner's little brother--heir to the throne--and his unusual appearance gives the locals cause to be weary.