A valkyrie (pronounced “VAL-ker-ee”; Old Norse valkyrja, plural valkyrjur, “choosers of the fallen”) is a female helping spirit of the god Odin. The modern image of the valkyries as elegant, noble maidens bearing dead heroes to Valhalla is largely accurate for what it is, but a highly selective portrayal that exaggerates their pleasant qualities. To some extent, this tendency toward sanitization is present even in the later Old Norse sources, which focus on their love affairs with human men and their assisting Odin in transporting his favorites among those slain in battle to Valhalla, where they will fight by his side during Ragnarok.
As far as we today can tell, 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. Examples of valkyries deciding who lives and who dies abound in the Eddas and sagas. 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. The Saga of the Volsungs compares beholding a valkyrie to “staring into a flame.”
This picture is confirmed when we turn to the lore of other Germanic peoples. Amongst the Anglo-Saxons, for example, the valkyries (Old English wælcyrie, singular wælcyrge) were female spirits of carnage. The Celts, with whom the Norse and other Germanic peoples engaged in fruitful cultural exchanges for numerous centuries, had similar beings of their own, such as the war goddesses Badb and the Morrígan.
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.
 An excellent overview of many of these examples can be found in:
Ellis, Hilda Roderick. 1968. The Road to Hel: A Study of the Conception of the Dead in Old Norse Literature. p. 69-73.
 Njáls Saga 156.
 Völsunga Saga 9.
 Ellis, Hilda Roderick. 1968. The Road to Hel: A Study of the Conception of the Dead in Old Norse Literature. p. 71.
 As noted in: Price, Neil S. 2002. The Viking Way: Religion and War in Late Iron Age Scandinavia. p. 334.
 Ibid. p. 345.