The Ring of Halcyon

The Ring of Halcyon #2 in The Outrider Chronicles, by Patricia Reamy

The Outridersare an elite group of warriors called by the Holy Spirit to protect God's sons and daughters. Ari Sommers and her friends are part of this group and must battle against the giant Nephilim, the enemy of God's children.  The ring Ari has been given may hold the secret to defeating the enemies.  She travels around the world to learn the secrets the ring holds.