Compare Lines 586-87 with those spoken by Satan in Book I: "The mind is its own place, and in itself Can make a Heav'n of Hell, a Hell of Heav'n."
1 answer
Are you certain you have the right line numbers? In 586-87 it is another example (following several) comparing Satan's victories over mortals, specifically Charlemain. I don't see a connection with the earlier lines in which Satan was justifying the greatness of Hell.