Polysyndeton is a literary technique in which conjunctions—such as "and," "but," and "or"—are used in quick succession, often with no commas, when the conjunctions could just as easily be removed.
The main effect of this technique is the generation of a certain tone, usually a very solemn one. Polysyndeton also emphasizes the words that are being artificially joined together through conjunctions. So, for instance, I could say, "I enjoyed dinner; I ate the chicken, and the salad, and the rice, and the mashed potatoes, and the bread." Normally, I wouldn't need to use the conjunction "and," but in polysyndeton I use it for emphasis to indicate how much food I ate.
In book 1 of Paradise Lost, we find the following example of polysyndeton [emphasis added]:
All is not lost; the unconquerable Will,
And study of revenge, immortal hate,
And courage never to submit or yield:
And what is else not to be overcome?
Though Satan has just been on the receiving end of a crushing defeat in the epic battle of Heaven, he is completely unrepentant. He's absolutely determined to rise again and take what he believes is his rightful place among the angels once more.
All the qualities he needs to make a comeback are listed in the above excerpt, joined together by the conjunction "and" instead of simply being listed as would normally be the case. This gives these qualities, which in this precise context are far from being noble, a certain dignity. Satan feels that he is the wronged party, and in this passage he is trying desperately to salvage some sense of pride from his recent defeat. Hence the use of polysyndeton, with its repetition of "and" reflecting Satan's pompous, magisterial self-image.