Revenge serves as a motivating factor for several characters throughout the poem, initially stirring Grendel and his mother. Grendel seeks revenge upon mankind for the heritage that he has been dealt. He delights in raiding Heorot because it is the symbol of everything that he detests about men: their success, joy, glory, and favor in the eyes of God. Grendel's mother's revenge is more specific. She attacks Heorot because someone there killed her son. Although she is smaller and less powerful than Grendel, she is motivated by a mother's fury. When Beowulf goes after her in the mere, she has the added advantage of fighting him in her own territory. As she drags him into her cave beneath the lake, her revenge peaks because this is the very man who killed her son. Only Beowulf's amazing abilities as a warrior and the intervention of God or magic can defeat her.
Revenge also motivates the many feuds that the poet refers to and is a way of life — and death — for the Germanic tribes. Old enmities die hard and often disrupt attempts at peace, as the poet recognizes. Upon his return to Geatland, Beowulf (2020 ff.) speculates about a feud between Hrothgar's Scyldings and the Heathobards, a tribe in southern Denmark with whom Hrothgar hopes to make peace through the marriage of his daughter. Beowulf is skeptical, envisioning a renewal of hostilities. In fact, the Heathobards do later burn Heorot in events not covered by the poem but probably familiar to its audience. Another example of revenge overcoming peace occurs in the Finnsburh section (1068–1159).
Beowulf's final battle is the result of vengeance. A dangerous fire-dragon seeks revenge because a fugitive slave has stolen a valuable cup from the monster's treasure-hoard. His raids across the countryside include the burning of Beowulf's home. Beowulf then seeks his own revenge by going after the dragon.
