Anachronistic Equipment
While most of the various axes and spears that you as the player will use to terrorize the people of England are period-appropriate, some of the weapons that make up Eivor’s armory are a little more suspect.
As mentioned, two-handed swords like the Doppelhander are entirely anachronistic during the period in which Valhalla takes place, as such long-bladed weapons weren’t used until the Late Middle Ages (1250-1500 CE). This kind of weapon would have been used more like a spear in actual use, a thrusting weapon as opposed to the wild slashes depicted in most video games.
Similarly, flails like the Iron-Star are around 150 years too early to the party, and historians think their use must have been exceedingly rare, even during the later Middle Ages. The unwieldy nature of the weapon, despite its fearsome appearance, would make it too much of a gamble to use on the battlefield in reality.
The inclusion of the Galloglaich set of armor is also ahistorical. This armor was worn by the famous Gallowglass mercenaries, of Norse-Gael heritage, but would not be seen on the shores of England until at least the 13th century.
The prevalence of chainmail too, amongst both Vikings and Saxon foot soldiers in Valhalla, would also have been unlikely, but this is a pretty common historical media sin. Such armor would have been incredibly expensive, as making it was a complicated and time-consuming process, and thus reserved for the nobility.