Hero Myths of the British Isles by Thomas Bulfinch

Notable among the names of heroes of the British race is that of Beowulf, which appeals to all English-speaking people in a very special way, since he is the one hero in whose story we may see the ideals of our English forefathers before they left their Continental home to cross to the islands of Britain.

Although this hero had distinguished himself by numerous feats of strength during his boyhood and early youth, it was as the deliverer of Hrothgar, king of Denmark, from the monster Grendel that he first gained wide renown. Grendel was half monster and half man, and had his abode in the fen-fastnesses in the vicinity of Hrothgar's residence. Night after night he would steal into the king's great palace called Heorot and slay sometimes as many as thirty at one time of the knights sleeping there.