Books in the Shadow chasers series

Only the Shadow Chasers, with their magical knives, can save the world from the evil that lives in the dreamworld. The powerful Oyo has a Shadow Chasers knife … and only the cleverest and bravest can withstand the Flame of Truth to win it back from her. With the guidance of Zulaika, a helpful ghost, Nom, Zithembe and Rosy travel through the unknown terrors of the dreamworld to find Oyo and regain the knife.