A terrifying monster with a "stinging tail," (17.1) rises up from the waterfall with a man's face but with a monstrous body of all sorts of colors, with two huge forepaws. The monster hangs at the edge of the cliff, whipping its tail through the air like a scorpion's. (Though not yet named, this is Geryon, a monster from classical mythology.) Virgil tells Dante that they must walk over to this beast. As they approach, Dante sees a group of souls sitting in the sand and Virgil tells him to go speak with them while he (Virgil) gets the monster to help transport them down below.
Once again, Virgil uses his skill with words to get a mythological monster to help Dante on his Christian journey. He encourages Dante to talk to the sinners sitting in the sand so that he can learn more about the various punishments of hell and perhaps begin to move from pitying such sinners to a pious acceptance of God's justice.
Dante goes alone to the souls sitting in the hot sand and does not recognize any of them. However, he sees that they all have purses tied around their necks, which they all stare at. Each individual's purse has a different image from his family's coat of arms. One of these suffering souls asks Dante what he is doing in hell and tells him to go away. Dante returns to Virgil, who tells him to mount Geryon. Dante is frightened and means to ask Virgil to help him hold onto the monster, but his voice fails. Virgil holds Dante securely anyway, and commands Geryon to fly down gently to the next circle.
These souls are usurers, whose obsession with money is punished in hell as they endlessly stare at their purses. The implication is that usurers are obsessed with money in life—making money their life—and so in hell they are made to do the same. Dante's fright temporarily takes away his ability to speak, though in recalling the event in his writing he is able to revisit the scene with his normal eloquence.
Geryon sets off from the cliff (Dante compares him to a boat leaving its dock and returning to sea) and Dante describes himself as being more terrified during the flight than Icarus was when he fell from the sky. They fly in gradually lowering circles, and Dante sees the seething waterfall at their side. Circling like a hawk, Geryon finally lands and sets Virgil and Dante down safely in the eighth circle of hell, before bounding off.
Dante compares his experience to the everyday world (with the boat) and the world of classical myth (with Icarus). By claiming that his ride on Geryon (a monster of Greek myth) is stranger and more terrifying than either he elevates his story, and the world of hell, beyond either the real world or the world of myth.