When Helgudin crossed the Rainbow Bridge, Olnir told her that she wasn't allowed into the magical ancient city behind the gates she guards. However, Helgudin isn't one to take no for an answer and her intentions aren't just to enter the city, she wants to rule it!
Helgudin is based on the Norse goddess of the underworld, Hel, with skills referring to other mythological beings: Kvasir, Nott, Loki, Baldr, and Fjalar and Galar.