Markshire suffered a terrible cataclysm that laid waste to the capitol of the country at the time, Arik. This incredible explosion caused the balance of magical power in the region to shift. Thrym (a real living and breathing but extremely powerful entity in Markshire) seized the opportunity to take control of the region and poured his power into the weather. He caused a blizzard that engulfed the region and killed many of the survivors of the cataclysm. Chaos ensued.
Odin watched and waited. The situation would eventually balance again but he decided to intervene and enforce the balance.
So he traveled to Elvidnir in Niflheim and brokered a deal with Hel. Instead of the Valkyries retrieving the souls of the worthy he would let them pass into Elvidnir. From there the individuals would be given a choice … they could re-enter the world and continue the struggle or pass on if the price was too great.
The price to continue was bargained and sealed. Garm, the horrendous two-headed hound that guarded the way to Niflheim, was remade and he was set to give the choice to the newly dead. The price was a piece of their soul which went to feed the fearsome Garm in exchange for rebirth in one of Odinâ€™s temples in Markshire.
This choice exists for any of the worthy marked by the Valkyries. The Valkyries are neutral in this and mark any soul that the Norns deem. Thus they mark the Chaotic and Lawful as well as the Good and the Evil.