
He finds him (the serpent), enters through his mouth, and waits until dawn.

He searches throughout the night for the serpent.He's not hoping to become happy because of what he's doing he just wants to make others as miserable as he is. It turns out, though, that Satan really can't enjoy it the whole thing just makes him mad.Before that, though, he bursts out in complaint, saying the earth is really beautiful "With what delight could I have walked thee round," he exclaims.He decides to become a serpent to execute his designs against Adam and Eve.There's a river (the Tigris) that flows underground and remerges as a fountain in Paradise Satan uses this river to get back into the garden.The sun sets and night falls as Satan returns – "fearless" and "bent on man's destruction" – to the garden.

The themes of those poems are "Not that which justly gives heroic name/ To person or to poem" (9.40-41).
