Despite Unferth's jealous rant at the first banquet, the most serious embodiment of envy in the poem is Grendel. The ogre who has menaced Hrothgar's people for 12 years is envious of the Danes because he can never share in mankind's hope or joy. The monster's motivation is one of the few undeniably Christian influences in the epic. Grendel is a descendant of Cain, the biblical son of Adam and Eve who killed his brother Abel out of jealousy (Genesis 4). The legend is that the monsters of the earth are Cain's descendants and eternally damned. Grendel resents men because God blesses them but will never bless him. The bright lights and sounds of joy emanating from Hrothgar's magnificent mead-hall, Heorot, especially annoy the ogre.
The scop's "Song of Creation" angers Grendel because it reminds him of the light and hope of God's creation and the loss he suffers because of Cain's sin. Grendel stomps up from the mere to devour Danes and rule nightly over Heorot as a form of revenge stemming from this envy.
