In 'Beowulf', Grendel did not show fear until Beowulf grabbed
him and would not let go. He realized BeowulfÃ?s strength was
stronger than his own and tried unsuccessfully to break free. When
finally he was dealt a mortal wound by Beowulf, he crawled back to
the swamp to die.
Grendel attacks Heorot, the mead-hall of King Hrothgar, on twelve separate occasions in the Old English epic poem "Beowulf". The attacks usually occur at night while the warriors are asleep.