Modthryth is not out there engaging in confrontation, as Grendel's mother does with actions, as Wealhtheow does with words, on account of someone else; she is nobody's mother. Her display of violence and her use of power are self-generated. [...] She reveals the trace of something that we know cannot exist in the world of the poem: the trace of a woman signifying in her own right. [...] She intrudes herself briefly into the poem's chain of signification, introduces unease, a thrill of disgust perhaps, a tremor of amazement at the unknown. The jolt in the narrative that she provides is just enough to make us think, as we watch the gracious temperate Hygd obediently perform her womanly duties, that one never knows...
Gillian Overing, Language, Sign, and Gender in Beowulf