Paradise Lost Book 2
Satan is sitting on his throne in Pandemonium, arguing that heaven isn't lost and asking the question left unanswered from Book 1: Should God be attacked overtly through war or covertly through guile? Moloch, one of the fallen angels, insists that he wants to wage open war with heaven, since nothing is worse than hell. Next, Belial speaks, contending that if the fallen angels don't anger God, he might remit their punishment. Since God's eye sees all, he dissuades both open and concealed war, reasoning that their present lot in hell is bad, but not the worst it could be. Once Belial finishes, Mammon speaks, arguing that it doesn't make any sense to worship someone you hate. Mammon advocates living to themselves in hell, "free, and to none accountable, preferring hard liberty before the easy yoke of servile pomp." Book 2, lines 255-7. This seems like the most popular idea so far, until Beelzebub speaks. He believes that Mammon is wrong: God will still rule them in hell. He advocates a new course of action: attack mortal man, who Beelzebub describes as, "less in power and excellence (than themselves), but favored more" by God. Book 2, lines 349-50. Beelzebub explains that the best revenge would be seducing men to follow Satan. The only problem is deciding whom they should send. Satan offers to go, saying that if he doesn't he won't be living up to his position as ruler. In this way, Satan parallels scenes later in which the Son volunteers for tasks others find undesirable (such as redeeming fallen mortal man).
With that settled, Satan sets off for earth, not allowing anyone to accompany him on his journey. He flies toward the gates of hell, but finds them impenetrable, and the guardian tells him to go away. The guardian turns out to be Sin, Satan's forgotten daughter. Sin is a grotesque combination of human and animal; she's a woman from the waist up, and a pack of dogs from the waist down. Sin informs Satan that she sprung out of his head. Satan then impregnated Sin with a son, Death, who proceeded to rape his mother. The product of that union is the pack of dogs that gnaw on Sin's bowels.
Satan, apparently now recalling his child/wife (Sin) and grandchild (Death) tells them about his mission and offers them a happy place to live in the new world of earth once it's conquered. Sin agrees to unlock the gates and let him pass, telling him, "thou art my father, thou my author, thou my being gav'st me; whom should I obey but thee, whom follow?" Book 2, lines 864-5.