Looking for a book written in the last 15 years (probably). Set in a medieval / Viking time but not necessarily our timeline. Main character is similar to Grendel in appearance: apelike, clawed hands, fangs, dark leathery skin. He is the last of his family/race, who are very violent. Possibly capable of hibernation or very long lived. The other main character is a human female who is a nun(?) who encounters the Grendel, is taken prisoner, then becomes a sidekick in the Grendel's quest for vengeance on somebody? There is travel in an open boat similar to a Viking long boat through stormy seas.