Beowulf is great because it combines the barbaric heroic code of the saxons but introduces a level of tension with christanity and new world values. Uses strict meter, imagery, and subject matter. the rest are very different from each other. Focus on historical trends that characterized the era (such as religion or empire or philosophy and schools of thought) think how these are distinct from each time period and then explain how they come across as unique (i.e. what litereary devices are most commonly used in each era).
