protector or destroyer. (shadow hunter fanfic)

a very old creature has lived on the earth for billions of years. Astria had a family and a great life but when your brother dies, you get corrupted and your sister can't manage the pain, how do you stay sane. she doesn't to some people because she has a ghost friend, MJ. he wanders around with her trying to find out how he died, who he is and why can Astria see him. When their past hit them like a wave can they manage on their owns I mean they have for the last 48 billion years or will they need help from the shadow hunters, demons, angels, downworlders (the people she has tried to stay away from.