Hel was the goddess of the dead and queen of Nifelheim/Helheim (the underworld) in Norse Mythology.
With a wave of her hand, she could cause disease, decay and death.
She was the youngest child of the god Loke and the evil giantess known as Angerboda. Her brothers were Fenris (the evil giant wolf) and Jormungand (the Midgard Serpent).
There was one rendition of the myth where Odin (since Loki was his blood brother) kept Hel with him to be raised in Asgard. But the other gods were uncomfortable with Hel's appearance (Hel was terrible to look at, one-half of her was greenish black and the other a livid white) and they avoided her.
Unhappy and lonely, Hel told Odin that she wanted to leave Asgard. Odin then gave to her the misty world of Nifelheim/Helheim to rule over.
It was those who died of sickness, old age, and those who did not die in battle that went to Hel's realm. She would judge those who were good and evil and give them their just rewards. (there were different levels of Helheim, ranging from a 'heaven' to a 'hell')