Religious event
"The Northman may be strong and bestial, but we should pity them! They need the Light of the Mantle brought to their homes, to their doors, to their families. They need to see the Light of goodness or the light of the purifying flame. Join me brothers and sisters, and we shall show the savages that our desire for peace is equally tempered with a drive for divine justice!" - Rohila Dahroe
The Fallen City of Balmoth had ongoing issues with raiding Norsemen for centuries. Even with the help of the local Dwarves the city couldn’t seem to stop the savage men of the north from continuously raiding their surrounding lands. In response a Paladin Lord named Rohila Dahroe rallied volunteers from Balmoth and called them on a holy crusade against the “Unholy” Norsemen. This crusade would continue off and on for over 20 years until Rohila was cast down by a savage werewolf. With the Crusaders bringing "religion" and "culture" back to the frozen Gir’An there was a cultural split in Norse Culture. After the Norse high chief/werewolf responsible for killing Rohila died chasing retreating Crusaders there was a succession crisis. The split was between traditionalists who wanted to keep things the way they were, new tribals who wanted to relent on their endless raids in the South and go back to their ancient shamanistic routes, and the Royalists who wanted to forge their own kingdom out of the North. This split resulted in an open civil war. There was no clear winner of this war, and all three cultures would split into disparate people. Many Norsemen would continue their raiding ways and continue to be known as the Gir'An. Meanwhile the new “Northern Tribes” would reconnect with the Earth around them and become more peaceful, if isolationist, nomads in the river valley in the Northeast. Finally the Royalists wound up forming their own small nation they called Holriad that sat between the Northern Tribes and the lands of the Gir'An. This split would remain until the early Third Age, until the formation of Nordanvald.