Sandsea trilogy

"Loulie al-Nazari is the Midnight Merchant: a criminal who, with the help of her jinn bodyguard, hunts and sells illegal magic. When she saves the life of a cowardly prince, she draws the attention of his powerful father, the sultan, who blackmails her into finding an ancient lamp that has the power to revive the barren land--at the cost of sacrificing all jinn. With no choice but to obey or be executed, Loulie journeys with the sultan's oldest son...