The Untold stories of the Rus Vikings

In the mid-800's A.D. they were centered around Novgorod. They dominated the area for over a hundred years. The Rus were led by Oleg, who captured Kiev, founding the Kievan Rus. The descendants were the ruling dynasty of Rus.

The Rus never attempted to conquer Scandinavia and held reasonably friendly relations with their Norse cousins. Things deteriorated first in the Middle Ages when Scandinavia became Catholic and Russia became Orthodox, and more importantly as their expansions started to collide. Some historians consider the portrayal of the Rus in the series as the first time the show's artistic license with history becomes downright offensive.

Their armor, helmets, and the fact that they seem to be immensely skilled horsemen is basically the Turko-Mongol empire of the Golden Horde centuries too early. Also, Prince Oleg's primary enforcer is a giant man with Mongol-style loop braids and a huge furry hate called Ganbaatar. While Turkic/Khazar bodyguards would be perfectly acceptable for this time period, Ganbaatar is a Mongol name (meaning something similar to "Steel Hero"), and the Mongols are way too far to the east to be known to the Russians at this time.