The Valkyries began in ancient Germanic belief and later made their way into the Norse cosmology, as the predecessors of the modern Germans--the Teutons--and the Norsemen of Scandinavia worshipped the same deities, but simply referred to them by different names. The Valkyries are a contingent of 13 warrior goddesses who have a very important role in the Norse schema: referred to as the Choosers of the Slain, they determine which warriors are deserving of entrance into Valhalla, an afterlife realm that serves as a warriors' paradise, which exists in a special section of Asgard. The Valkyries appear in the skies over battlefields where followers of the Norse and Teutonic faiths are engaged in brave combat for a cause they believe in. Virtuous mortals who bravely fight for what they believe in utilizing means other than the proverbial sword (such as the famous pen) who follow and revere the Norse path and its deities are likewise potentially eligible for entrance into Valhalla following their physical demise. These heroic and virtuous spirits become known as the Einerjar, with half of them ruled over in Valhalla proper by Odin, the king of the gods, and the other half going to dwell in another section of Valhalla known as Folkvangr, where they are ruled by the powerful goddess Freya. The Valkyries are said to serve mead (or its astral equivalent) to the heroes in Valhalla, and they are attendants of both Odin and Freya. Freya may have served as the prototypical inspiration for the Valkyries, and she has been described as their leader in various sources. The non-heroic dead who followed the Norse path are ignored by the Valkyries, and they are under the province of the death goddess Hela, where the common dead dwell in the afterlife realm Helheim (or simply Hel--not to be confused with the Christian Hell) and the dishonored dead dwell in a frozen afterlife realm called Niflheim, both of which are ruled and controlled by Hela.
The Valkyries have been described in the myths and other legends as tall women with long hair decorated in braids and garbed in warrior raiment. They carry spears with the blades plumed by flame (spears being of significance to Odin, as he wields one himself), riding in the skies on winged horses that resemble Pegasus of Greek mythology. The manes of their horses are said to drop dew upon the ground. They are associated with ravens, who symbolize death in different mythos, and are also said to be able to shape shift into swan maidens. Upon choosing a slain warrior (the word "warrior" being broad in modern terms) to be worthy of entrance into Valhalla, a Valkyrie will greet their soul upon the person's demise and escort them--along with Hela (though she has no jurisdiction over souls chosen by the Valkyries)--to the realm of the heroic dead, and sometimes other afterlife realms that their soul may have had a preference for (such as Summerland, the Wiccan equivalent of Heaven). The most well known Valkyrie in the mythos is Brunhilda (often spelled "Brunnhilde,' and also called Sigdrifa in some sources), who is said to lead the Valkyries in "the field" (i.e., the skies over battlefields), and figures prominently in the myth involving the Norse hero Sigurd, where he encountered her after she was stripped of her immortality and placed in a sleep spell by Odin after falling in love with a mortal man, a serious breach of the rules for a Valkyrie. Upon being released from the sleep spell by Sigurd, Brunhilda became his lover and instructor in the wisdom of the Nine Worlds, including the mysteries of the runes. The saga of Sigurd, including the story of Brunhilda and the consequences of her relationship with him, figures prominently in the famous 19th century German composer Richard Wagner's four part operetta The Ring of the Nibelung, which includes his famous instrumental "Ride of the Valkyries." It has been said in some sources that Thrud, the warrior daughter of Thor and his wife Sif, also became a Valkyrie. The Valkyries figure very prominently in Germanic and Scandinavian artwork and sculpture for the past several centuries.
I have often tried to build a strong spiritual bond with the Valkyries, and it's more than worth doing so, as they have knowledge of the meaning of death, what lies beyond for mortal consciousness, and the wisdom regarding combat, both literal and metaphorical (which can apply to activism, social conflict of a major sort, etc.). They can be called upon to deliver messages to those who have passed on; accordingly, I recently called upon Brunhilde to deliver a message to an aunt of mine who had just passed away, to let her know how much I will miss her and that I really regret not being able to spend more time with her during her final years. They can also be called upon to guide you and calm you when death approaches for someone you care for, along with your own inevitable death. They have a large degree of knowledge of other aspects of the universe, too, due to the particular metaphysical circles they regularly walk within, but the lessons they have to teach and the knowledge they have to pass on, which are done entirely on their own discretion, of course, can be more than the unprepared would expect, so they should be called upon with caution by the uninitiated. They can also be called upon to turn a combat situation in your favor or in the favor of an ally, as they have a strong warrior aspect to them that enables them to turn the tide of a battle in favor of one particular side. They can also influence an individual's wyrd, which is a Germanic word alluding to fate. As such, the Valkyries have a highly important role to play within the Norse cosmology, and they therefore more than deserve a page of dedication to them on this shrine.