The Day Watch

This is the second volume in Sergei Lukyanenko's trilogy. After Alisa, a Dark One, loses her powers in a minor confrontation with some Light Ones, she heads to the Crimea to recuperate at a girls' camp, where she feeds on children's nightmares. There she falls in love with Igor, who turns out to be a Light magician. The plot centers on the ramifications of their romance and the theft of Fafnir's Talon, a powerful artifact whose provenance is linked to the legendary Ring of the Nibelungs. (from Amazon.ca)