Val'kyr

Val'kyr are a type of undead vrykul, and seem to be a recent addition to the armies of the Scourge and later the Forsaken. They act as the Lich King's agents in the spirit world, being described by Thoralius the Wise as being "fearsome creatures made of pure nightmare" that "now stand watch over the realm of the elements".

Background
The val'kyr originate at an unknown point in time, but seem to predate the Lich King. The vrykul bard, Helgus, lived in the town of Nifflevar and wrote three sagas, one of which was the Saga of the Val'kyr. This is ancient knowledge. It is unknown if other mentions of the val'kyr in the Fjord are references to ancient details, or are direct references to the Lich King's then-current forces. The val'kyr are "warrior maidens of old" and "each was the greatest warrior of her generation".

They are sisters who "served the warriors of the north in life, and chose to continue [their] service in death." They were bound to the Lich King, though they did not have a choice.

The modern val'kyr are a creation of the Lich King. They were created from the female vrykul of Valkyrion, who fought and trained to receive the Lich King's unusual "gift". At least one example exists of a female vrykul being turned into a val'kyr at another location as well. Those that were deemed worthy underwent the transformation from simple vrykul to val'kyr. It is said that the val'kyr serve to judge the fate of vrykul combatants, transforming the favored contestants to Ymirjar, and the failed contestants to the ranks of the undead Vargul.

Beyond this, the Val'kyr Battle-maidens also watched the fates of the training death knights of Acherus, making sure the newly born warriors didn't fall in battle before their time. In fact, these val'kyr were acting much like the spirit healers of the undead Scourge. If they fell in battle, the val'kyr would return them to their unlife. During the Battle for the Ebon Hold shortly after the death knights are freed, aiding the remains of the Scourge.

The Val'kyr named Annhylde the Caller is a part of the Ingvar the Plunderer encounter in Utgarde Keep. Upon Ingvar's death, Annhylde judged Ingvar and found him unworthy. Annhylde resurrects him as Vargul and begins phase two of the fight giving him a second chance. Fjola Lightbane and Eydis Darkbane are two very powerful Val'kyr that were originally sent by the Lich King along with their Vengeful Val'kyr army to disrupt, destroy, and terrorize the Argent Tournament and its citizens. But during this attack Argent Confessor Paletress comes to the defense of the tournament and battles the twins. Paletress is victorious, and Fjola and Eydis are captured. Their bonds are maintained by Priestess Alorah and Priest Grimmin. They later appear as the "final" challenge of the coliseum after the raid has defeated the Faction Champions.

Edge of Night
After the events took place within the Icecrown Citadel, and the death of Arthas, only nine val'kyr remained in the world. These nine, lead by Annhylde the Caller, were bound to the will of their new dormant Lich King. Imprisoned atop the Icecrown, possibly for eternity, they hungered for their freedom. To gain this freedom they need a vessel, one like them, a sister of war, strong, and who understands life and death. Someone who has seen the light and the dark. Someone worthy of power over life and death. Sylvanas Windrunner, after having just committing suicide off the Frozen Throne, was shown what would happen to her people and herself if she was gone, using this information they convinced her to make a pact with them. In this pact the val'kyr would be free of the Lich King forever, but their souls would be bound to the Dark Lady. Sylvanas will walk with the living once again, but through the sisterhood of the val'kyr. As long as they lived, so too will Sylvanas. All of them will have their freedom, life, and power over death.

Sylvanas agreed to this pact, if only to prolong her fate, which filled her with terror. Annhylde took Sylvanas's place in death as the pact was made and the remaining eight sisters were bound to their new leader.

Part of the Forsaken
The Forsaken had one major flaw working against them; they could not reproduce. The Lich King was the one who created the Scourge, and now that the Lich King was gone, there were no Scourge left to turn to Forsaken. The val'kyr were her salvation and solution to her dilemma. Since the val'kyr could raise the undead, they were essentially the key to keeping the Forsaken "alive" as a viable race. After leaving Northrend, a few of the val'kyr were sent to the Deathknell Graves to "recruit" any remaining corpses there into the Forsaken, while the Dark Lady made her way to Silverpine to prevent her people from being slaughtered by Garrosh's command. With her were the rest of the val'kyr making their presence known.

After Garrosh backed down and allowed Sylvanas to take command of the campaign for Gilneas, Sylvanas had decided that her people would no longer be carelessly used or squandered away for some orc. They would be used wisely and with a purpose, as a bulwark to safeguard her and their kingdom. A bulwark that grows stronger as the val'kyr raises the living's dead to bolster their numbers, even with former enemies joining their ranks. This is due to the fact those raised by the Val'kyr who die in combat or under extreme stress, enter into a violent, frenzied state. Undead in this state are easily manipulated and their rage is often directed at the foes of those who raised them. After the effects wear off, the remaining resurrected are given the option of joining the Forsaken or being returned to the grave.

The val'kyr themselves have been deployed into several battles since their conscription, notably throughout Silverpine and Andorhal, both of which were sound Forsaken victories due to the val'kyr's input. However, the val'kyr were only able to reanimate human corpses as Forsaken. The humans trapped in the conflict with the Forsaken sought to escape that fate by turning into worgen, and thus the surviving leaders and refugees of Hillsbrad Fields and Southshore were willing to take the worgen curse and became Hillsbrad Worgen to prevent the Forsaken from raising them into undeath.

When Sylvanas was killed in Silverpine Forest, Agatha, Arthura and Daschla sacrificed themselves to revive her once more. Then later in the battle at Andorhal, the Alliance would kill Aradne, thus leaving only four val'kyr in existence. It's unknown where they currently are, but they're likely in a safe area continuing to raise more Forsaken members.

Appearance
Val'kyr are angelic in appearance. They have clear, ghostly, light blue skin. Their hair colors are usually dark, but some are gray or white. Val'kyr wear a heavy breastplate, underwear and sandals.

Trivia

 * Lesser val'kyr have been shown to join the Horde. They are unable to revive Sylvanas Windrunner if she dies, but they can raise new forsaken.