The Ring of Eagna

In tenth-century Ireland, a monk records the legend of a mythical treasure that can only be accessed with three ancient rings. A thousand years later, Ciarán and Aodhán Donnelly discover the manuscript and are convinced the tale refers to the relics of their fifth-century priesthood. But the tome warns of dire consequences for any who attempt to retrieve the fabled cache without the rings.
Ciarán and Aodhán expected no less of their priestly ancestors, so they’re not in the least bit deterred. After all, they already have two rings. All they need to do is locate a third, and they can recover the hidden artifacts for the museum.
Their light-hearted treasure hunt turns deadly, however, when they discover they’re not the only ones searching for the trove of sacred artifacts. Worse yet, it becomes all too clear that their rivals will stop at nothing to win the prize. First, however, the would-be thieves will need to acquire the rings Ciarán and Aodhán already possess, and the brothers have no intention of relinquishing them without a fight. But are they up to the task of defeating these unknown brigands or will their past finally catch up with them?