Hel

Hel was the name of both the Norse underworld, and it's ruler, Queen Hel. Hel (the location) was located at the bottom of the World Tree. It was the home of those souls whose lives and deaths did not allow them to go to one of the other deities--primarily those who died of illness or old age.

Resources:
Misty Forest:
Tree:
Lady:
Ghosts:

Kudos to anybody who can identify which ghost is which!