Answer:
Beowulf is the prince of the Geats, who comes to the aid of King Hrothgar of the Danes as his kingdom is besieged by a monster called Grendel.
Beowulf defeats Grendel, but Grendel's mother comes for revenge and Beowulf goes underwater to fight, and kill her. However, he discovers that his weapons are useless against her, and finally kills her with a large sword made by giants on the wall.