A valkyrie (from Old Norse valkyrja "chooser of the slain") is one of a host of female figures who decide who will die in battle. The valkyries bring their chosen to the afterlife hall of the slain, Valhalla, ruled over by the god Odin, where the deceased warriors become einherjar.
There, when the einherjar are not preparing for the events of Ragnarök, the valkyries bear them mead. Valkyries also appear as lovers of heroes and other mortals, where they are sometimes described as the daughters of royalty, sometimes accompanied by ravens, and sometimes connected to swans.
The valkyries have always had such characteristics, but in heathen times they were far more sinister. The meaning of their name, “choosers of the slain,” refers not only to their choosing who gains admittance to Valhalla, but also to their choosing who dies in battle and using malicious magic to ensure that their preferences in this regard are brought to fruition.
The valkyries’ gruesome side is illustrated most vividly in the Darraðarljóð, a poem contained within Njal’s Saga. Here, twelve valkyries are seen prior to the Battle of Clontarf, sitting at a loom and weaving the tragic destiny of the warriors (an activity highly reminiscent of the Norns). They use intestines for their thread, severed heads for weights, and swords and arrows for beaters, all the while chanting their intentions with ominous delight.
Whether in their loving or bloodthirsty modalities, the valkyries are best understood as part of the extensive and dynamic complex of shamanism that permeates pre-Christian Germanic religion. Much like the ravens Hugin and Munin, they’re projections of parts of Odin, semi-distinct beings that are parts of his larger being.