I assume you are referring to Hel, the Goddess of the UnderWorld and Death from the Norse pantheons. Hel is the daughter of Loki and the giantess known as Angrbodha. The Gods came together when trying to figure out what to do with all of Loki's offspring. They ended up bringing Hel to live with them. Because of Hels appearance (which I will later describe) her life was very difficult. The other Gods were so uncomfortable about how she looked that they largely avoided her, and this caused her great grief and despair. Hel became an oddity, of sorts. Because of her misery, Hel went to Odin and asked permission to leave Asgard. The other Gods decided that she would be given the world/realm farthest away from the World Tree- Helheim ("House of Hel").
Through PCPG (and my own experiences) a lot of common traits about her have been summarized. (If you want to get a good indepth look at some of this she has a whole chapter devoted to her in Raven K's Jotunbok). She is very dutiful of her work, and protective of the dead. While she does allow seidhr-workers to speak with the dead (if they are willing) she doesn't generally like anything that would bother them, and prefers them to be left alone. Which would explain why Helheim is said to be so strictly guarded (Garm is a giant hound who is said to guard the entrance. He is sometimes equated or thought to be a representation of Fenrir, another wolf from Norse mythology. It depends largely on which texts you read and the translated versions of them. Garm is usually shown as having multiple eyes, soaked in the blood of the dead, with vicious white fangs protruding from his mouth. Another curious inhabitant of Helheim is Modgud- who serves Hel by guarding the bridge that leads into/out of the underworld. She is usually shown as a giant woman, large in stature and build.)
Hel's appearance is one of the more interesting things about her. She tends to look like she is cut in two meaning that one part of her is whole and the other is rotting or skeletal. Now, where the division is sometimes varies according to people who have worked with her. Some see the division as being straight down the middle, separating right half and left half, while some see the division as being sideways. When I've visualized her it's always been down the middle. I think it's very symbolic, of death even. It represents the peaceful and ugly side of death. The light and dark side of each individual. The end of something, and the beginning of something else. Some people view Hel to be this scary, dark deity- which she can be- but I think it's important to note that she is lovable as well. She tends to get regarded as being a "dark" deity simply because the nature of death is sometimes viewed as "dark". But she has good, and "light" aspects to her just as death does. She is not a pitying deity, and she does not appreciate lying. With Hel, everything is blunt and straightforward- simple, really.
I've incorporated her into a lot of my workings, as she is the Goddess I spend the most time working with. I don't think she is right for everyone. She can be quirky, so it takes a certain type of person to be able to deal with that. But I've called upon her for cursing nidstangs, for protection, for helping a friend who has passed, for guarding a sick friend, for seidhr-work, Val-galdr and so on. Working with her is simple as well! She is not a deity who requires a lot of trinkets and offerings or shiny doo-dahs. If you want to offer her some things, she likes: jewelry, blackened or dried flowers, bones and blood, and fear (yes, an emotional offering). Food offerings and such are not really her "thing", but if you want to offer food you can do so. Typically when offering something to Hel you either bury the offering in the ground, leave it permanently on the altar or you burn it. Altar wise, she normally does not have a big altar. Its quite common to make what we call a "Hel jar". It's a small jar that you paint, then fill with some offerings to her, and leave on a shelf. That's your altar for her.
All-in-all, she's my favorite Goddess. I have more personal experiences with her, but I call them personal for a reason. If you'd like to discuss it, though, I wouldn't mind exchanging some mail. Best of luck to you. :)