What might grendel symbolize?

To really understand what Grendel symbolizes we must also examine some of the many Biblical references in the poem. The story of Cain and Able is of particular note. You know, as in Cain and Able the first murder and all that. Cain killed his brother Abel out of jealousy and was cast away. . Grendel is supposed to be a descendent of Cain. He sits away in a murky swamp jealous of all the merriment and mirth of Hrothgar’s subjects. Grendel is jealousy drives him to kill as many people as he can. It’s kind of like Cain only more of a mass murder. The connection always struck me as a little weak but the audience of the time would have had no problems with the association.