Animation company Oriental Light and Magic (OLM) landed the contract to adapt Emily Rodda's stories because they were the only studio to promise her they would not change or alter the story.
Originally in the book series, one of the main heroes, Lief, had black hair, and another, Jasmine, had black hair as well. Lief's hair was changed to blonde to better convey that he was the main protagonist. Jasmine's hair was changed to a dark green.