Making their way to the Seventh Pouch of the Eighth Circle of Hell, Virgil and Dante face many dangers. Because of the collapsed bridge, they must navigate treacherous rocks, and Virgil carefully selects a path before helping his mortal companion along. Dante loses his breath for a moment, but Virgil urges him onward, indicating that a long climb still awaits them. They descend the wall into the Seventh Pouch, where teeming masses of serpents chase after naked sinners; coiled snakes bind the sinners’ hands and legs. Dante watches a serpent catch one of the sinners and bite him between the shoulders. He watches in amazement as the soul instantly catches fire and burns up, then rises from the ashes to return to the pit of serpents.
Virgil speaks to this soul, who identifies himself as a Tuscan, Vanni Fucci, whom Dante knew on Earth. Fucci tells them that he was put here for robbing a sacristy—the Seventh Pouch holds Thieves. Angered that Dante is witnessing his miserable condition, he foretells the defeat of Dante’s political party, the White Guelphs, at Pistoia.
Cursing God with an obscene gesture, Fucci flees with serpents coiling around him, and Dante now relishes the sight. Moving further along the pit, he and Virgil behold an even more incredible scene. Three souls cluster just beneath them, and a giant, six-footed serpent wraps itself so tightly around one of them that its form merges with that of its victim; the serpent and soul become a single creature. As the other souls watch in horror, another reptile bites one of them in the belly. The soul and the reptile stare at each other, transfixed, as the reptile slowly takes on the characteristics of the man and the man takes on those of the reptile. Soon they have entirely reversed their forms.
Having recognized these thieves as Florentines, Dante sarcastically praises Florence for earning such widespread fame not only on Earth but also in Hell. Virgil now leads him along the ridges to the Eighth Pouch, where they see numerous flames flickering in a deep, dark valley. Coming closer, Virgil informs Dante that each flame contains a sinner. Dante sees what appear to be two souls contained together in one flame, and Virgil identifies them as Ulysses and Diomedes, both suffering for the same fraud committed in the Trojan War.
Dante desires to speak with these warriors, but Virgil, warning him that the Greeks might disdain Dante’s medieval Italian, speaks to them as an intermediary. He succeeds in getting Ulysses to tell them about his death. Restlessly seeking new challenges, he sailed beyond the western edge of the Mediterranean, which was believed to constitute the rim of the Earth; legend asserted that death awaited any mariner venturing beyond that point. After five months, he and his crew came in view of a great mountain. Before they could reach it, however, a great storm arose and sank their ship.
Early in Canto XXIV, Dante clarifies the geographical structure of Malebolge (the Eighth Circle): it slopes continuously downward, so that, after the Tenth Pouch, it runs right into Hell’s central pit. Virgil and Dante have thus not been simply progressing around the underworld’s circumference but descending deeper and deeper into the Earth’s core.