Background:
Hel is referenced in the Prose Edda, written in the 13th century by Snorri Sturluson, various times. In chapter 34 of the book Gylfaginning, Hel is listed by High as one of the three children of Loki and Angrboða; the wolf Fenrir, the serpent Jörmungandr, and Hel.
High says that...