Cloud Fortress of Twilight — Linda Regula

Having forgotten how to use imagination, twelve-year old Lindy Cooper has also forgotten her imaginary friend and protector, Princess Twilight, who, lost in a dark void of forgotten memories, waits for her creator to find her. Lindy discovers a mighty stone fortress in the clouds where she meets its Lord Keeper, begins an exciting quest to find a lost Golden child, rides a cloud traveler across a magical starfield, and teaches a dragon hatchling to fly.