Watch Grendel for Free: How to Stream the Movie Online at 123Movies. . King Higlack of the Gauths entrusts prince Finn and a fire ball weapon to his champion, slayer Beowulf. They lead twelve men on a mission to help king Hrothgar of the Danes, whose once glorious realm is terrorized by the undefeated monster Grendel. The task is made more difficult as Hrothgar kept gruesome secrets.