Recognizing him as Italian, a soul, by moving the tip of its tongue of flame asks Dante to tell him the state of things in Romagna, from which he comes. Dante tells him of endless warfare between the nobles there, and begs to know his name. The soul answers, "If I believed my answer were to someone who would ever return to the world, this flame would remain still. But since never from this depth has anyone returned alive, if I hear true, without fear of infamy I answer you" (lines 61-66). Still, he does not say his name (Guido da Montefeltro), but simply tells his story. While he was young, he played the fox, and was famous for his knowledge of all the tricks and deceptions that are effective in the world. As he got older, he repented and became a Franciscan friar, and that would have meant his salvation, if Pope Boniface VIII hadn't sent for him to ask his advice on how to get the best of an Italian family he was feuding with. When Guido didn't answer, Boniface absolved him ahead of time for any sin, boasting of his power as pope to control who would get into Heaven. Guido advised him to promise and then break his promise. When Guido died, St. Francis came for him, but a devil got in first and claimed him, pointing out that absolution does no good without repentance first, and it's obvious one hasn't repented if one goes ahead and does the deed.
The passage quoted above was used by T.S. Eliot as the epigraph for The Love Song of J. Alfred Prufrock. It illustrates here how deep the infamy of these souls is. "Politics as usual" was no excuse in Dante's eyes for this misuse of human intelligence. The advice Guido da Montefeltro gave was that the pope should promise to spare the city he was fighting if they surrendered, and then should go ahead and destroy the city. Boniface did just that.