Grendel's mother stays away from Heorot until she finds out that her offspring Grendel has been killed. She wishes to avenge her son's death. The"swamp-thing from hell" (1518) lives in an underwater lair where Beowulf bravely confronts her. It is in her lair where she meets her demise at the hands of Beowulf:

Then he saw a blade that boded well,
a sword in her armory, an ancient heirloom
from the days of the giants, an ideal weapon,
one that any warrior would envy,
but so huge and heavy of itself
only Beowulf could wield it in a battle.
So the Shieldings' hero hard-pressed and enraged,
took a firm hold of the hilt and swung
the blade in an arc, a resolute blow
that bit deep into her neck-bone
and severed it entirely, toppling the doomed
house of her flesh; she fell to the floor.
The sword dripped blood, the swordsman was elated. (1557-1569)