On an unknown date in (perhaps) the 860s, Norse raider Ragnar Lodbrok (or Ragnar Lothbrok) was allegedly put to death in the Indiana Jones-esque manner of being cast into a pit of snakes. Ragnar is a half-legendary character who plundered France and Britain in the mid-ninth century, the heyday of Viking marauders; he’s also the lead character of the cable TV series Vikings. He’s known from Scandinavian sagas, like the Ragnarssona Þattr, which describes Ragnar’s final battle after shipwrecking in Northumbria.....