How does evil manifest itself in Beowulf?

How does evil manifest itself in Beowulf?
How does heroism manifest itself in Beowulf?

From the story up to Grendel's mother, i saw alot of mentioning of God and something about banishment in the story. For example, when it mentioned Grendel at the start it talked about Abel's death. I am not particularly sure who Abel is, but i think he might be some sort of demon like Satin. Abel was banished and he split into a thousand different manifestation as evil spirits. He was like the embodiment of evil, therefore it somehow became the nature of Grendel. It is the origin of Grendel that made himself the manifestation of evil for the people in Beowulf.
As for the manifestation of heroism in Beowulf, he on the other hand acquired the characteristics of God. At lines 310 to 315 mentioned all kinds of things how Grendel was caught in the iron grasp of Beowulf. Beowulf's presence was a sure grip on evil's throat. The story described Beowulf in all kinds of shimmering light as the protector or the strongest man on earth. Heroism itself slowly manifested in the character Beowulf.
The notion of Justice triumphant over Evil is once rooted in alot of people or stories. When evil is being punished like Grendel, the idea that people have in mind is that Beowulf is justice. If it is not justice and heroism that Beowulf represents, then what could possibly have triumphant over evil? These ideas are implanted throughout the start of the story to describe the roles of the different characters. In fact, alot of the places in the story clearly defines the evil and heroism in Beowulf.