Grendel’s mother is a monster who is described as “wife of trolls.” She is a terrible beast that lives deep in the depths and rarely comes out, but she mourns Grendel’s death.
She was doomed to dwell in dreary waters and cold streams ever since Cain cut down his only brother, his father's son, with his sword-edge. (ch 19)
Grendel’s mother is not given a specific name, further reinforcing the fact that she lives through her offspring. She is described as “bloodthirsty and grim,” and driven to avenge her son’s death.
She is not afraid, because she is so driven to take revenge on the men. She thinks of nothing but killing as many of them as possible. Beowulf is not there when she tears through the hall, but is able to go after her and kill her. He follows her, the guardian of the lake, without malice. She is a horrible monster, but she is still a mother and her hatred of her son’s killers is understandable.