Could you please provide details that would support the claim that Grendel is a flat character in "Beowulf"?
Grendel is considered a flat character because we don't know much about him. Characters who are round pop off the page--we know their thoughts, actions and motives behind them, how they look and dress, their speech, and how others react to or think about them. We are able to relate to these round characters because all of us know someone like this person. Grendel, however, is a sort of mystery. The story is not told from his perspective, but rather an objective third person narrator. We know he is descended from Cain, the first murderer, which makes him more evil and worthy of the audience's "hate" since one of the ideals of the Anglo-Saxons is loyalty to family above all else. We have vague descriptions of his appearance...moreso for the fear factor of every reader (it's scary to everyone when each individual has to picture what makes the monster scary to him or herself) than lack of character development. We know he lives with his mother in a cave far away from humans, and we know he attacks Herot because the warriors are noisy and he dislikes it. Other than that, we don't know anything about him. We are just expected to take that he is evil due to his illogical reasoning for attacking the men and his lineage. In addition, we can not relate to him since he is completely alien to the human experience. He simply helps to move along the plot, but he does not pop off the page.