The Cloud Kingdom: A Branches Book (the Last Firehawk #7)

Now that Thorn has been defeated, Tag and his friend Skyla embark on a new quest, to find Blaze's lost family and the other firehawks who disappeared through a portal to the Cloud Kingdom; but the Cloud Kingdom is full of new dangers, and when giant birds seize Blaze and carry her off Tag and Skyla are left to try and free their friend-with only a magic map to guide them, and the threat of the shadowy shape that seems to be following them.