Vrykul

Vrykul are a race of half-giant warriors native to the Howling Fjord, located in southeastern Northrend.

Background
It is said that in ancient times the vrykul race inhabited the land, founding a vast and prosperous civilization. Suddenly, without warning or explanation, the vrykul race vanished, leaving behind only deserted villages and abandoned temples. Due to the encroachment of the Alliance settlement of Valgarde on their lands, vrykul have recently returned.

Led by King Ymiron, these formidable warriors have begun attacking Horde and Alliance settlements from the fortress of Utgarde Keep, not far from Valgarde. Vrykul motives and their whereabouts for the past several thousand years remain a mystery, though they have recently become allied with the Lich King, accepting him as their "Death God".

Vrykul are brutal in nature, and are served by worgs and a similarly mysterious race of proto-dragons. They practice a runic magic that even the most experienced wizards find unfamiliar. For some reason, they frown on manual labor, thinking it lowly.

Vrykul children born in a certain time after their gods "abandoned" them, approximately 15,000 years ago, were "weak and ugly". King Ymiron ordered all those children to be killed, but not all of the parents obeyed this command, instead hiding their children in order for them to grow up far away from Northrend. This evidence that vrykul are the progenitors of humans.

A dialogue uncovered by Brann Bronzebeard in Ulduar lists the vrykul (along with the earthen and the giants) as "seed races", implying that they are direct creations of the titans as opposed to having evolved from some other race over time.

The Cataclysm
A group of kvaldir is found in Vashj'ir. A group of normal vrykul seem to have joined the Twilight's Hammer under the command of Warmaster Blackhorn. Both he and them can be fought during the fight against him in the Dragon Soul raid. Archaeologists can learn more about vrykul through vrykul artifacts.

Mists of Pandaria
Lorewalker Cho shows the adventurers their ancestors of their respective race. Forsaken adventurers are shown to vrykul, appearing as their furthest ancestors and confirming humanity's evolutionary lineage.

Ruben Holen in the Shrine of Two Moons mentions the Pandaren having books about the vrykul but he doesn't know how they could possibly have encountered them.

Appearance
Vrykul appear as very large and muscular humans, usually with beards.

Cairne Bloodhoof (who had never seen one in person) describes them as such: "They looked like humans—if humans were larger than tauren and sometimes had skin that was covered in ice, or made of metal or stone."

Culture
The frost vrykul believe that wearing a necklace of polar bear claws will grant them otherworldly strength.

Subraces

 * Frost vrykul
 * Sea vrykul
 * Iron vrykul
 * Stone vrykul
 * Val'kyr
 * Vargul

Trivia

 * It can be speculated that the disappearance of the vrykul can be traced back to the Sundering if they, like the earthen, were greatly affected by the event and retreated to hibernate for thousands of years. This possibility may be seen in Jotunheim and Gjalerbron where some of the vrykul are in a state of hibernation. The Tribunal of Ages hints that Loken put them in stasis at the end of his war.
 * Although the vrykul are generally seen as an inherently brutal race, focused on nothing but violence, power and servitude to their king, there are several cases where a disobedience to power, whether it be king or magic, is seen. A a vrykul couple choose to save their "weak" and "ugly" child (as they were described by King Ymiron) out of what appears to be the same moral values that their human descendants hold.
 * Vrykul are heavily inspired by Norse mythology and culture.