She has many names but her most known name is Hel. There had been prophecies about three children who would bring terrible disaters but would bring nothing but evil. Loki had a giant named Angrboda have his children, three children to be exact. The first was Fenrir the wolf, the second Iromungard the midgard serpent, and then finally Hel. They were raised in Giantland for some time before Odin found out about the children and told the gods to retreive the children and bring them to live in Asggard with them. The only one who did not adapt well to living in Asggard was Hel because she had be born with half her body showing her bones, the onther gods were uncomfotable around her and mostly avoided her. She was sad and lonley so she asked Odin if she could leave, and him taking pitty on her gave her the realm of the Dead to rule. He named it Helheim after her, and in return she had to care for the souls of those who had died of old age and sickness or any non violent way, the souls of warriors were sent to Odin and Freyja, who between the two split the share of souls in two. She was the one who judged the souls of those who passed through there and depending on how good or evil they were she gave them a place in the nine levels of Helheim, it ranged from the top being heaven all the way doewn to the ones being for the most wicked of people. Some thought that her appearence was thought to represent life and death and might have started harlequin masks. Theres a story about how she can be a bit maternal and kind and helping but she can also be harsh and cold to those who disrespect her and try to stop the natural order of things.