Skandar and the Spirit War

Skandar and the Spirit War by A.F. Steadman.

To defeat Rex, Skandar and his friends will need to look back to the origins of the Island, and harness the full power of their elemental magic. Can Skandar become the leader he needs to be – to save the Mainland and the heart of the Island itself? Get ready for unlikely heroes, elemental magic, sky battles, ancient secrets and ferocious unicorns in this highly anticipated adventure that will keep you reading after lights out!