Lilith is Lucia's mother. She once worked under a Professor Dermeil with Lucif and Nahashi to learn the magic arts, and in the anime after their mentor died, their training ceased. Lilith fell in love with Lucif and eventually became pregnant with Lucia, though by the time she was born, Lucif was already gone on his quest for the True World.
Protective of Lucia. Nahashi described her as very nice.
Lilith has long blond hair that ends below her waist, and blue eyes.
Lilith doesn't appear in the first 14 chapters of the manga, though she is mentioned in Chapter 7 by Nahashi when he is talking to himself about the symbols on Sumire being similar to those on "her."
In Chapter 16 we get a glimpse of Lilith when Lucia asks Nahashi about her mother.
In Chapter 22 we get a glimpse of Lilith's life by Nahashi reading her diary. She gave him the nickname Nachash because she couldn't pronounce his last name. We also find out in this chapter that Lilith was a berserker like Sumire, the berserker effect coming on if a virus managed to injure her.
A Virus allegedly killed Lilith when Lucia was still two years old. The Virus that killed her was Lucif, who did so in order to obtain her special fragment, although in the end, the fragment disappears. She sacrificed herself to protect Lucia and the world that Lucif wanted to destroy.