Dante and Virgil find a way down from the precipice into the seventh circle, but their path is blocked by the minotaur, a half-bull, half-human creature of Greek mythology born from the union of a woman and a bull. Virgil insults the minotaur, and it goes mad, thrashing about at random, allowing Dante and Virgil to sneak past it.
Dante borrows the monstrous minotaur from Greek mythology (where it is defeated by the hero Theseus). Here, Virgil overcomes it with nothing but his clever use of language.
Virgil explains to Dante that the path down through the cliffs was created by the massive earthquake when Jesus went into the first circle of hell to rescue certain souls. He says that at that moment, the universe "trembled in the throes of love," (12.42). Virgil then points out the river Phlegethon, full of boiling blood, where those who committed violence against others are.
The power with which Jesus made hell quake is seen in terms of the divine love that is the basis for the entire universe. The juxtaposition of this idea of love with the tortuous imagery of the Phlegethon may seem jarring, but part of Dante's point is that even the horrible sufferings of hell are (as paradoxical as it may seem) ultimately the result of God's love. Having to be immersed in boiling blood to the degree that matches up with the amount of violence one committed in life seems a fitting punishment, indeed.
Dante sees centaurs (half-man, half-horse creatures) all around the banks of the Phlegethon with bows and arrows. Upon seeing Dante and Virgil, one of them stops them and orders them to identify themselves and their punishments in hell. Virgil identifies this centaur as Nessus, and rebukes him. He then points out to Dante the centaur Chiron, who taught Achilles, and another centaur named Pholus. Virgil explains that the centaurs stand guard at the banks of the river to prevent any suffering souls from escaping it.
Virgil recognizes the centaurs as creatures of classical mythology. Dante has them guard the banks of the Phlegethon, helping to carry out Hell's punishments. The centaurs are hostile until Virgil speaks to them.
Chiron notices that Dante is a living soul and Virgil explains to him that he is leading Dante on a quest through hell ordained by heaven. Virgil asks Chiron to help them across the river and asks a centaur to let Dante ride him as they ford across the river. (Unlike the dead souls who can walk on air, Dante would be unable to walk across the boiling river.) Chiron has Nessus help them across the river.
Chiron is surprised by Dante's transgressing the borders between the living and the dead. The oddness of Dante's position is emphasized when he has to ride Nessus across the river, whereas the dead souls can merely float across on the air.
While walking along the riverbank, Dante looks at some of the souls submerged in the river and Nessus points out where the tyrants are in the river. He identifies Alexander the Great, among others. Further along the river, Nessus shows Dante Guy de Montfort, who murdered Prince Henry of England. Nessus, Dante, and Virgil come to a shallow part of the river, where they can cross. After crossing, Nessus describes how the river gets deeper and deeper and at its deepest completely submerges tyrants like Attila the Hun. He then turns to go back to the other centaurs.
In mentioning the names of great historical figures like Alexander the Great, Dante helps record their fame, while also contributing to his own: their presence in his poem and on his journey magnifies the grandeur of his own story. At the same time, placing these heroes in Hell also glorifies God, as these heroes must, like everyone else, submit to the order of God's universe and accept punishment for sins against God's moral order.