As the Queen of Hell, Hild represents all that is dangerous and evil in the world of Ah! My Goddess. Unfortunately, she also happens to be the Demon mother of Urd. When Urd requests that she come to the Morisato Residence to help solve a problem, she complies, but then continues to remain on Earth.

Class: Obviously first class, she's the ruler of hell. ^-^
First appearance: Chapter 134
Weakness: None, except maybe Urd (as she is still her mother)

Overview
Hild is the most powerful demon in the series, being the counterpart of the Almighty. The various ornaments on her hair, arms and legs serve to hold back her power, analogous to Belldandy's seal earring. She first appears in Chapter 134. Urd is Hild's daughter by the same father as Belldandy and Skuld.
Not much is known about her.