The first and primary villain in the ancient, Anglo-Saxon
(which had nothing to do with computers, dammit). He is supposedly descended from Cain's side of the Biblical family and lived with his mommy
in a lake near Hrothgar's hall in Denmark till Beowulf the Geat came, ripped his arm off, killed his mother, and took poor Grendel's head as a trophy.
Other good sources on Grendel are John Gardner's book (Grendel
) and http://grendel.org/ .