Hel

In Norse mythology, Hel is queen of the underworld of the same name. daughter of Loki and Angrboða makes her a sibling to Fenrir  and Jörmungand.

She is half blue and half flesh colored, somber ruler of her realm. She was appointed in her position by Odin, presumably to keep her busy from causing trouble. Other Loki's children received somewhat similar fate, as Fenrir was chained and Jörmungand sunken beneath the oceans.

Hel as a person
In her demeanor Hel is cold, bordering on cruel. It is her responsibility to house whoever is sent in her vast halls of the dead in Hel. She has many servants in her realm, whom to she delegates minutia details.

The most famous example of her dominion is when Baldur has died by an accident orchestrated by Loki. Hermod, a messenger of the Aesir, comes with pleads of Baldur's return to the world of the living. All of the gods have wept for Baldur's untimely death.

Hel is not convinced only the grief of gods is good enough of a reason to let anyone outside of her domain. She is willing to let Baldur go if every living and every unliving thing in world would weep for Baldur.

Then nearly everything in the whole of existence wept for Baldur, including smallest of rocks. Sole exception was one stubborn giant, who was most likely Loki in disguise.

Realm of Hel
Depending on interpretation, Hel is one of the nine world of the cosmology of Norse Mythology with entrance in Niflheim, or the whole place is located in Niflheim. Either option lends itself to description where Hel is beneath one of the roots of Yggdrasill, the World Tree that holds the nine worlds connected to each other.