Origin

Hela is the daughter of Odin & an unknown Goddess. There are rumors that she may be the daughter of Loki but this has not been confirmed. When she came of age she was granted the rulership of the northernmost kingdom of the dead. Her dominion was only over those who did not die as heroes, Odin was the ruler of these in Valhalla. Seeking to expand her kingdom waited for the chance to take over. When Odin's attention to Valhalla waned she had her chance. Once he was aware of her intentions a great battle took place. Hela corrupted the Valkyries causing them to lose their physical form & remain in a wraith like state. Danielle Moonstar was also stuck in this state, she & the New Mutants journeyed to Asgard to battle Hela's army. The battle with various forces brought the Hulk and Agammemnon, the leader of the Pantheon, to Hela's realm. After a long fight against Hela's surreal forces, Agammemnon requests, based on a vaguely hinted upon relationship, to allow them to leave. Hela surprisingly agrees. This incident sheds light on the fact that in Marvel, Hela is supposedly the half sister of Agammemnon. The fighting continued on until the mutants were able to wake Odin.

Powers

Hela was all of the typical Asgardian traits including super strength, immunity to disease, enhanced metabolism & resistance to most injuries. Her control of the dead allows her to kill someone with a touch including a healthy Asgardian but she is usually content to wait until the person is already dying. She also possesses the power to return the recently deceased to life but very rarely uses this gift. Hela is also able to travel in astral form for unknown periods of time. She also has the power to bring back to life from her realm, whoever she wishes though she doesn't use this ability often.

Much of Hela's power beyond that of normal Asgardians, especially those over death, stems from her cloak. When the cloak is taken from her, it is revealed that she herself is half dead already, half her body rotted away. She even loses her physical strength. This doesn't mean she requires to wear the cloak since a touch from the cloak replenishes her power.