What is significant about the fact that Grendel attacks at night, and what descriptions associate him with death or darkness?
Grendel’s nightly attacks are made to fit in line with the popular conception that evil or danger strikes under the cover of darkness. Thus, the fact that Grendel only attacks at night compounds the image that he is an evil monster out to torment innocent people.
At that time in history, nighttime was meant for relaxation and socialization, and the Danes did this at Herot. However, Grendel takes the opportunity to torment the people when they seek to enjoy peace after the routine activities of the day.
Grendel is described as a powerful monster that stays in the dark, yearning to attack the people. The monster is stated to have haunted the moors and the marshes. He is said to have been a descendant of murderous creatures born of Cain after Cain was banished by God for killing his brother, Abel. The Danes try to appease Grendel, but the monster continues his murderous spree until Beowulf comes to their aid.
Till the monster stirred, that demon, that fiend, Grendel, who haunted the moors, the wild marshes, and made his home in a hell not hell but earth.
It is significant that Grendel attacks at night because he is described as being evil and the darkness symbolizes that evil. Grendel is described as being the spawn of Cain (the Biblical character who was the first murderer). Also, Grendel's nighttime attacks make him seem more sinister because he attacks while the warriors are sleeping - they are helpless at the time. He is called the monster of evil, he leaps and laughs after killing thirty men, and he continues to come back night after night.
The following lines from section II have more language that supports Grendel's link to death and evil.
The monster of evil fiercely did harass,
The ill-planning death-shade, both elder and younger,
Trapping and tricking them. He trod every night then
The mist-covered moor-fens; men do not know where
Witches and wizards wander and ramble.
So the foe of mankind many of evils
Grievous injuries, often accomplished,
Horrible hermit; Heort he frequented,
Gem-bedecked palace, when night-shades had fallen
One of the devices the Beowulf poet uses are kennings, or compound phrases that function as a noun and further re-name a person or place by describing them in an interesting way. One use of a kenning is to help enhance characterization. For example, throughout the poem, "hell-forged hands" is used to describe Grendel. The imagery suggests a creature who was created in hell, which clearly connects to death and darkness. Grendel is also referrred to by the kenning, "Almighty's Enemy", another reference to his evil nature.