The Battle of Evernight: The Bitterbynde, Book 3, Part II (Unabridged)

Once upon a time, the great Faeran high king, Angavar, became trapped in mortal Erith, along with his twin brother and nemesis, Morragan, "the Raven Prince". It was when the gate to the Faeran Realm was closed on them. Now, many centuries later, the fugitive who calls herself Tahquil has at last discovered the truth. She is being hunted down by the Raven Prince, because she alone can reopen the gate to the Fair Realm, so Morragan plans to use her for his escape from exile. However, Tahquil's mind is still clouded by a potent spell called the Bitterbynde, and she is also dying from a mystical wasting disease. The cure, and the final answers to the mystery of her past, can only be found in Evernight - at the fortress of the Raven Prince himself.