Sif is a mythical Goddess of old Scandinavian Lore. She's the Goddess of fertility, marriages and family to name a few things. Not to mention that she's the lady wife of the mighty Tor, mother of the noble and powerful Ullr, Trud, Modi and stepmother to Magni. She may not be a fierce warrior in battle, as a stark contrast to what Marvel has adapted to their portrayal of her. But she rules the home and family as fiercely as the mightiest of bears.