Who are you calling a troll? The Grendel in question in Beowulf & Grendel, a muscular, ardently naturalistic retelling of the ninth-century Anglo-Saxon saga, may be on a bloody tear, and Tomb Raider 2’s Gerard Butler rattles a lot of heroic chain mail. But Canadian-Icelandic director Sturla Gunnarsson focuses on the more interesting psychology of tribalism — as well as on the moderating influence of a witchy woman, played with usual confrontational sass by Sarah Polley. As demanded by the public in any movie with Nordic (or piratical) content, Stellan Skarsgard growls heartily as Hrothgar, king of the Danes. B