Inferno section 16: Dante and Virgil approach a waterfall cascading into the lower regions of Hell. As they approach the falls, three spirits leave a group of spirits because they recognize Dante's garb as Florentine. The three spirits belong to Guido Guerra, Tegghiaio Aldobrandi, and Jacopo Rusticucci-all notable patriarchs of Florence who belonged to Dante's political party. The spirits wish Dante much fame and ask if Florence has changed. Dante responds with regret, "Newcomers to the city and quick gains have brought excess and arrogance to you, o Florence, and you weep for it already!" As they retreat, the spirits ask Dante to speak of them when he returns to Earth. Dante and Virgil make their way to the waterfall. Virgil asks Dante to give him the coil wrapped around his waist. Virgil tosses the coil into the waterfall to signal the beast that will carry Dante into the depths below.
Inferno section 17: "Behold the beast who bears the pointed tail, who crosses mountains, shatters weapons, walls! Behold the one whose stench fills all the world!" Dante announces as Geryon, the monster summoned by Virgil to escort Dante past the waterfall, appears. Dante describes Geryon in vivid terms: the face of an old man with gracious features, the trunk and tail of a serpent, two paws, and hair up to his armpits. Virgil instructs Dante to talk to a group of spirits sitting by the waterfall while he convinces Geryon to be their escort. Dante pauses to talk to the spirits who occupy a separate zone of the Seventh Circle, set aside for those who were violent against Nature and Art (Usurers). The Usurers also suffer from the flakes of falling fire but the also wear pouches around their necks. On each pouch sits a different crest. These crests are the only things that differentiate one spirit from another because their faces are indistinguishable. The Usureers do not treat Dante kindly. One spirit sticks out its tongue at Dante who retreats quickly to rejoin Virgil. Dante mounts Geryon who takes him on a terrifying flight to the landing below. Upon setting the poet down, Geryon flies away like an arrow.
Inferno section 18: "There is a place in Hell called Malebolge, made all of stone the color of crude iron, as is the wall that makes its way around it." Thus, begins Dante's journey through the lower regions of Hell. Malebolge means "evil pouches." Ten pouches, aligned in concentric circles, make up the Eighth Circle where "ordinary fraud" is punished. Dante and Virgil first see a deep valley where sinners who were panderers or seducers walk constantly in both directions as horned demons flog and torment them. Dante recognizes one sinner and calls him by name, Caccianemico. This sinner tells of how he arranged for the seduction of his own sister. Dante and Virgil continue across the first chasm and come to the second chasm where flatterers are sunk in excrement. Dante recognizes Allessio Interminei who explains that he is sunk to the top of his head because in life he could never stop his flattery. Upon seeing the woman, Thais, who flattered her lover extravagantly, the poets move away into the next area of Malebolge.
Inferno section 19: The third chasm of the Eighth Circle holds the Simonists, clergy members who trade the favor of the church for money. Deeply opposed to papal interference in public life, Dante takes this opportunity in the book to rail against these sinners. The Simonists must spend eternity upside down in holes. Protruding from holes, the legs and feet of these shades burn with flames. Dante sees one spirit suffering from more pain than the others. He approaches the spirit to find that it belongs to a pope (Nicholas III). Dante reproves Nicholas by recounting the story of Jesus and Peter who asked for no money when they chose Matthias to take the place of Judas. Virgil, pleased by Dante's tirade against the pope, carries Dante across this chasm to a bridge above the next valley.
Inferno section 20: In the fourth pouch of the Eighth Circle, Dante finds the Diviners, Astrologers, and Magicians who all tried to foretell the future-a sin against God's plan. With their heads placed backwards on their bodies, these shades must spend eternity walking backwards. Dante meets Manto, the sorceress who founded the city of Mantua, Virgil's birthplace. Manto tells the long story of the founding of Mantua. Virgil points out other shades in this realm: Eurypylus, Michael Scott, a writer of occult sciences, Guido Bonati, Asdente, and numerous women who became women. Virgil hurries Dante as the moon sets.