Grendel is a fictional character, a creature defeated by Beowulf in the Old English poem Beowulf from 750 ce...
Grendel symbolizes evil and jealousy.
Descended from the biblical Cain, Grendel is an outcast, doomed to wander the face of the earth.
Grendel represents evil, so the poet's Christian worldview turns him into a fiend from hell.