Tennyson's "Idylls of the King" are written in stichic rather than stanzaic form. The section on the death of Arthur describes a final battle and the promise that Arthur will return again.
If you are struggling to read and understand the poem, you might first consider reading Malory's account of the death of Arthur, which was the source for Tennyson's poems.
Next, as you read through the assigned lines, you should be able to summarize it yourself through two main reading strategies. The first is to mark out syntactic (grammatical) units and read one clause at a time, rather than letting yourself get carried away by the rhythm. Second, as you read every sentence, write down a paraphrase in your own words, looking up any words you do not understand. By doing this, you will not only understand the poem better, but you will have trained yourself to read Victorian poetry more easily.