The Sword of Light by Heather Graham

Will fabled objects of myth be enough to defend their emerald isle?
The mystical Tuatha Dé Danann walked the hills of ancient Ireland long before the first Rí, or king, ever ruled the land. Before they stepped back to make way for mankind, they left behind objects of incredible power that would reveal themselves when most needed. When invaders from the North arrive, it feels like the moment that has long been foretold has finally come.

Deidre, the daughter of a Rí, and Kylin, the son of a Northman who found peace and a home in Éire, have little in common, until they begin seeing visions of these fantastical gifts. The revelation that a traitor exists among the many Irish kings forces them to work together using their newfound powers in defense of their homeland. As all they hold dear comes under threat, it may be more than just dreams that the two begin to share…