Arkas has short hair and an equally short beard and dark, sunken eyes. Two scars run from his eyes to his ears. Another scar runs vertically across the forehead. 
Before he became a Stormcast Eternal, Arkas was called Arka Bear-clad, due to the black bear pelt he wore. One of his greatest achievement was to unite the constantly fighting warrior clans of Ursungorod in the Realm of Ghur, why he was also called the Uniter. Besides that he wore several further names and titles such as the Bear of Hard Winters, Savior, and the Fang of Freedom. 
Arkas' home was the city of Kurzengor, an immense town at the foot of Mount Vazdir. During a besiegement of the city by the Skaven of Clans Pestilens, Arkas was claimed by Sigmar. The Skaven host was led by Verminlord Skikaxoth, who had killed Arkas' mother and sister many years earlier. Before the ratkin were reaching the battlements of Kurzengor, an azure lightning bolt ascended Arkas. Deprived of their leader and facing the superior force of Skaven, most of the defenders of Kurzengor fled. 
Arkas and his Warbeasts are renowned for being undisciplined and hot tempered. Arkas himself describes his temperament as intuitive and his leadership style as leading from the front line of battle. [1a]
As Stormcast Eternal, Arkas was once again sent to Ursungorod to conquer the realmgate below Mount Vazdir. During this endeavor, however, Arkas was slain by Skikaxoth, who still dwelled underneath the ruins of Kurzengor. After his reforging, he returned fiercier than ever and, using his animalistic bond with Ghur, spiritually awakened an ancient avatar in form of an immense celestial bear that split open Mount Vazdir and exposed the formerly subterranean Skaven city and realmgate to the surface.