Simple, he eats them. Beowulf says:
"If Grendel wins, it will be a gruesome day;
he will glut himself on the Geats in the war-hall,
swoop without fear on that flower of manhood
as on others before. Then my face won't be there
to be covered in death: he will carry me away
as he goes to ground, gorged and bloodied;
he will run gloating with my raw corpse
and feed on it alone, in a cruel frenzy,
fouling his moor-nest." (442-450)
Beowulf had no help he slaughtered Grendel on his own in the fen.
“Staggering under the weight of Grendel’s skull,Too heavy for fewer than four of them to handle-Two on each side of the spear jammed through it . . . “
Grendel killed 30 men the first night he attacked Heorot Hall.
The battle between Grendel and Beowulf takes place in Heorot, the hall of the Danes.
Grendel is able to kill 30 of Beowulf's men in the mead-hall, Heorot.
Grendel attacks Heorot, the great hall where the people are fighting, killing many men.
Grendel's mother takes Grendel's claw and Hrothgar's closest friend, Aeschere, after she attacks Heorot.
Grendel killed 30 men during his first visit to Heorot.
Beowulf and Grendel fight at Heorot, the great mead hall of King Hrothgar in Denmark. The battle takes place in the darkness of the night while the warriors are sleeping, and it is a fierce and brutal encounter.
Beowulf travels to Heorot because he heard tales of Grendel and the deaths of Hrothgar's men. He wants to defeat Grendel, these motivations show that he desires to prove his strength and the might of the Geats.
Grendel terrorized Heorot by launching nightly attacks on the warriors there, killing and feasting on them. His presence instilled fear and chaos among the people, making Heorot a place of suffering and despair.
Beowulf and Grendel fought in the mead hall of Heorot, where Grendel had been terrorizing Hrothgar's warriors. The battle took place at night when Grendel attacked the hall, and Beowulf vowed to rid the hall of the monster.