Who is the Danish warrior killed by Grendel's mother?

The Danish warrior killed by Grendel’s mother is Aeschere, also written Æschere. He is one of King Hrothgar’s closest advisers and trusted companions in Beowulf. His death is the immediate consequence of Grendel’s defeat and represents a deliberate act of revenge.

After Beowulf kills Grendel, Grendel’s mother attacks Heorot, the Danish hall. Her raid follows the heroic code of blood-feud: the death of her son demands compensation through the death of one of his enemies. She seizes Aeschere and carries him away, while also reclaiming Grendel’s severed arm.

Hrothgar is especially distressed because Aeschere is more than an ordinary fighter. He is described as a wise counsellor, a man who understands the king’s affairs and helps explain difficult matters. Beowulf and his companions later find Aeschere’s severed head near the entrance to Grendel’s mother’s underwater lair.

Aeschere is not killed in the final underwater battle. Beowulf follows Grendel’s mother to her mere, kills her with an ancient sword, and then finds and beheads Grendel’s corpse. Common mix-ups include Hrothgar, who survives, and Unferth, another Danish court figure who remains alive.