Reginheim

Valkyries:

Names:	Proto-Germanic: *Walakuzjoz ("Choosers of the Fallen") Western Germanic: Valkyries (English), Waelcyrige (singular: Waelcyrge)(Anglo-Saxon), Walküren (singular: Walküre)(Dutch and German), Walkyren Northern Germanic: Valkyrjur (singular: Valkyrja)
Appearance:	In the oldest legends the Valkyries are female spirits riding on wolves, later sources changed them into beautiful women in armour riding through the air on horses.

The Valkyries are female spirits who ride on wolves with snakes as reins, a belief that is reflected on the Rök stone where the word "Valkyrie horse" is used as a kenning for "wolf".
Just like their master Wodan/Odin they enjoy battle and carnage and after a battle they appear together with the wolves and the ravens to eat the corpses.
The Valkyries also weave a war-web of the material that was left behind on the battlefield like weapons and dead bodies;

Njal's saga, Darraðarljóð:

Vítt er orpit fyri valfalli
rifs reiðiský rignir blóði;
nú er fyri geirrum grár upp kominn
vefr verþjóðar er þær vinur fylla
rauðum vepti Randvés bana.

Sjá er orpinn vefr ýta þörmum
ok harðkléaðr höfðum manna
eru dreyrrekin dörr at sköptum
járnvarðr yllir enn örum hrælat
skulum slá sverðum sigrvef þenna.

Blood rains from the cloudy web
On the broad loom of slaughter.
The web of man, grey as armour,
Is now being woven; the Valkyries
Will cross it with a crimson weft.

The warp is made of human entrails;
Human heads are used as weights;
The heddle-rods are blood-wet spears;
The shafts are iron-bound, and arrows are the shuttles.
With swords we will weave this web of battle....

The Valkyries also take the spirits of the fallen and bring them to Asgard where they are divided between Odin and Freya, not much is known about those who are chosen by Freya but the warriors taken by Odin are brought to Walhalla ("Hall of the Fallen") where they are invited to join the Einherjar, Odin's elite army that will fight the forces of evil at Ragnarök, until this time the "Honourful Dead" passed their time with training their fighting skills, drinking mead, and celebrating.
Valkyries are also used by Odin to transfer messages and in many legends the hero receives help or advice from a Valkyrie sent by him, the hero Siegfried (Sigurd) even marries Brünhilde (Brynhild/Sigrdrifa), who is also a Valkyrie.
In later periods the Valkyries were romanticized into beautiful women on horseback, which is still the most popular image of them, but originally they were more like invisible scavenging spirits.
According to Scandinavian folklore the Aurora Borealis (or Northern Light) is caused by the flickering armour of the Valkyries and there are even some unverifyable stories from the last two world wars about soldiers who saw women riding in the mist above the battlefield, but these stories are probably nothing more than urban legends.