Sonji

Despite the threat of theft, Astra enters the Great Desert Race of Dryzza ... only to be left horseless in the middle of nowhere. Thieves believe her white mare, Sonji, is the key to the treasury of the Palace of the Creator. Two desert dwellers and a voice on the wind lead Astra and her friend Hamal to the legendary palace. There, they meet the Creator. He listens to their story and helps them-but for repayment he asks Astra to convince her mother to answer his summons. Rumors of those heeding a summons and never returning home haunt Astra as she agrees.
The Creator returns Astra, Hamal, and Sonji to the race. And when Astra keeps her promise to him-the Creator surprises her.