Grendel's mother

Plot Importance
Grendel's mother is Beowulf's second foe. Her first mention is in ft. XIX, and her clash with Beowulf occurs in fts. XXII-XXIII.

She lives in a cave beneath a lake full of monsters. She comes to Heorot after the death of Grendel to avenge her son, killing a man and stealing Grendel's arm which had been placed in the hall as a trophy. Beowulf follows her to the cave and after a well-matched battle, kills her with a sword he finds there.

Background and Description
Though her origins are never fully confirmed, Grendel's mother is said to have "dwelt in those dreadful waters,/the cold streams, ever since Cain/killed with his blade his only brother" (ll. 1260-62), implying a reasonable connection between herself and this original murder (as depicted in the Christian Bible), and also implying that she is at least a few centuries old. Despite her long-lasting presence in the world, it is also said that she had only "held that expanse of water/...for a hundred half-years," which brings to light that her arrival in the grotto near Heorot had been relatively recent (especially when compared to her enormous lifespan).

Her physical strength and prowess are astounding, as is shown multiple times: Grendel's mother can only be slain by one particular sword which Beowulf encounters in her grotto. This sword is unnamed, but is remarked to be "greater than any other man/might even bear into the play of battle" (ll.1560-61).
 * when Beowulf attempts to bash her with a sword immediately upon encountering her, but discovers only that "the battle-flame would not bite,/or would her fatally". (It is suggested that this sword is either cursed or that Lady Grendel is enchanted to somehow prevent that particular sword from injuring her.)
 * when Beowulf attempts to remove her arm in the same manner as he did Grendel's only to find that her joints are far more secure than her son's.