When I decided that the protagonists of my second novel would be a family of Continental Saxons, I turned to Beowulf as a source, even though I had no intention of including any mention of the poem, its characters, or its plot.
Why? I needed something that showed Saxon culture, and there is little written source material from that time. The Church had done everything it could to obliterate the pagan religion in Saxony, and the Continental Saxons did not have a written language as we know it.
But we have Beowulf, created sometime between the seventh and 10th centuries by an anonymous poet of a similar ethnicity. And what a gift it is to a historical novelist. Because of the poem, I understood my characters’ deep desire to avenge the wrong done to them was not only personal but cultural. I understood that even though they agreed to be baptized, the influence of pagan beliefs would linger.
But Beowulf’s creator might have drawn on more than his own culture. See my post at English Historical Fiction Authors for my speculation about the epic’s origin.