Books in Cloud Kingdoms series

Zaeyen objects to the marriage her father has arranged for her, although she understands this is his way of helping the dukedom of Noor to survive. The groom threatens Zaeyen and she runs away to search for the elusive Eos. In the past these ghostly beings interacted with the land to keep it healthy and fruitful, but they disappeared over a century before and now the whole planet is dying. Kade, a hero of the common folk, meets Zaeyen in the wilderness and is amused by her attempt to disguise her true identity. He realizes she has no idea where she's going, and joins her to help or hinder, depending on the real reason for her journey. By the time he finds out the truth about there quest his emotions have become entangled in hers and he has no choice but to help her find Eos. Thirst, hunger, capture -- all these bar their way to success. It's not all bad, though, as they journey also brings them into contact with people who can help them on their quest. Will they find Eos at the end of their journey and if they do, will the spirits be willing to return to the human world?