They had earned. Here, darkness is associated with Beowulf's previous battles. He is brave and strong enough to enter the world of darkness to fight and conquer evil on its own turf. Still death taking more and more. In this description of Herot after Grendel's massacres, a definite contrast of light and dark imagery is presented.
Daylight is associated with humanity's rule.
Darkness and night is associated with evil and Grendel's bloody raids. Hrothgar's warriors face the darkness and the evil, but when the light of day comes, only their blood remains. 50, lines 849-852 Darkness, Grendel's death, and his evil nature are directly connected. Repeated throughout the text, the connection between darkness and evil is strongest in the physical description of Grendel's lair, where his body was deposited. A sense of relief and peace returns, as hell receives Grendel's body.