"As noble as his name. So should all men raise up words for their lords, warm with love, when their shield and protector leaves his body behind, sends his soul on high. And so Beowulf's followers....."
Notice the alliteration in the phrases "words for their lords" and "warm with love." How would you describe the tone of these lines?
This section of the text comes towards the end, when Beowulf has died and his followers bury him, having received both a pagan cremation and then being buried in a more Christian ceremony. The tone of these lines is one of noble mourning, as the followers of Beowulf express fitting homage to the lord and master, recognising the greatness of his character and remembering the feats he committed. Consider the lines that come straight after this quote and how they add to this tone of nobility and respect:
And so Beowulf's followers
Rode, mourning their belovèd leader,
Crying that no better king had ever
Lived, no prince so mild, no man
So open to his people, so deserving of praise.
This is clearly a section where grief is deeply felt, as witnessed through the repetition of "no better king" and "no prince so mild." It is clear that this section creates a tone of sombre respect and mourning that the various examples of alliteration that were identified in this question help to support and establish. The grief and serious mood is almost palpable through the words chosen, the alliteration, and the structure of the sentences, including the repetition of key phrases.