All were endangered; young and old
Were hunted down by that dark death-shadow
Who lurked and swooped in the long nights
On the misty moors; nobody knows
Where these reavers from Hell roam on their errands.

Beowulf, Seamus Heaney (trans.)

Lines 159-163: The passage describes the terrifying effect Grendel has on the Danes, with his ability to come and go unseen in the night to murder them.