What is the universal theme identified in Beowulf?
The term universal refers to all. In this sense, no universal theme exists within the epic of Beowulf. In order to define a theme as universal, everyone must identify the same theme. That said, Beowulf does contain multiple themes which tend to be the most identified themes by readers.
Glory and treasure exists as a theme of Beowulf. This idea runs throughout the whole of the text as readers "hear" of Beowulf's previous battles, his victories over Grendel and his mother, and Beowulf's desire to have any treasure sent to his home if he perishes during any battle. Even on his deathbed, Beowulf asks Wiglaf to go and get the dragon's hoard in order for him to gaze upon it.
Wyrd (or fate) is another important theme of the epic. Constantly, readers are reminded of Beowulf's lack of fear given he knows that God controls his fate. He enters into every battle knowing that the winner will be the one chosen by God. He accepts that his life has already been planned by God.
Loyalty is a characteristic which the Anglo-Saxon culture prized highly. This said, if one were found to disgrace one's lord, vengeance was expected. Essentially, these concepts worked hand in hand. Readers see Beowulf's loyalty to his own king through his request for his treasures to be sent to his homelands if he is killed by Grendel's mother. At the same time, he loyalty never falters in regard to Hrothgar either. He stated that he (Beowulf) was in the Danelands in order to rid Heorot of evil, and he upheld his loyalty to this promise.