Because he is greedy and wants revenge. He feeds off of there bodies.
After the feast at Herot, Grendel attacks the warriors in the hall at night, killing many of them. This cycle of attack and retaliation continues until Beowulf arrives to defeat Grendel.
Grendel was angry at Herot because the noise and celebration from King Hrothgar's mead hall disturbed his peace and quiet in the nearby swamps. He felt envious of the joy and camaraderie of the people inside the hall, leading him to attack and terrorize them.
The warriors of Herot are celebrating and listening to the bard's song about the creation of the world. This angers Grendel and in his first attack he kills 30 sleeping men.
There is a weeping man.
Herot is a mead hall in Beowulf, a famous Old English poem. In the story, Herot is attacked by the monster Grendel, who terrorizes the hall and its occupants for many years. Beowulf eventually arrives and defeats Grendel, bringing peace back to Herot.
Grendel
Grendel's hatred of Herot stems from feeling excluded and rejected by the people inside. He is an outsider, living a lonely existence in the wilderness, and the celebration and joy in Herot serve as a constant reminder of his isolation and lack of belonging. This, combined with the noise and revelry that disturbs his peace, fuels his anger and drives him to attack the mead hall.
Grendel attacked Heorot Hall at night, sneaking in during a celebration that lasted for 12 years, causing death and chaos among King Hrothgar's warriors.
In the epic poem Beowulf, the titular character is called upon to help the men of the Heorot mead hall, which is being terrorized by the monster Grendel. Grendel is a demon who eats men who is apparently motivated to attack because of hearing songs coming from the hall that detail God's creation of earth.
grendel attacks the people who are in it by "the moon" (at night)
Herot remained empty for 12 years because grendel attacked all the warriors & would continue to attack even kill anyone who would go to the mead hall
Beowulf hangs Grendel's arm after he rips it off. Beowulf hangs Grendel's arm after he rips it off.