Eaters of the Dead / Michael Crichton

The year is A.D. 922. A refined Arab courtier, representative of the powerful Caliph of Baghdad, encounters a party of Viking warriors who are journeying to the barbaric North. He is appalled by their Viking customs - the wanton sexuality of their pale, angular women, their disregard for cleanliness...their cold-blooded human sacrifices. But it is not until they reach the depths of the Northland that the courtier learns the horrifying and inescapable truth: he has been enlisted by these savage, inscrutable warriors to help combat a terror that plagues them - a monstrosity that emerges under cover of night to slaughter the Vikings and devour their flesh....

Eaters of the Dead was adapted to the screen as The 13th Warrior, starring Antonio Banderas.