This serial killer that we're looking into... Hlin mentioned they may be killing people that had fled the lotteries, lotteries used to determine who would be sacrificed to the Frostmaiden. These sacrifices are meant to appease her and bring an end to the eternal winter but there have been sacrifices to her before.
I was a child. Not even a teenager. My mother was a chieftain. She tried to kill me, she threw me into the Sea of Moving Ice to either freeze or drown. A sacrifice to Auril the Frostmaiden. I should have died but I was saved by a bear, no, a goliath that walked as a bear. Oyaminartok.
I'm sure somewhere in her twisted mind she was in the right but how can anyone good try to murder their own child? What if my daughter lives in one of the towns that sacrifices people? I would watch the world freeze to death and die a thousand deaths myself before I would willingly let harm come to her. Bjornhilder of the Tiger is not my mother, she is a monster just like Auril.