Dante asks the shade who he is, and he answers that he came recently from Tuscany, where he lived the life of a beast. He is Vanni Fucci of Pistoia. Dante asks what his crime was, for he had seen him once and considered him to be a man of violence. The spirit, ashamed, confesses that it hurts him more for Dante to see him here in this dreadful place than it did to be condemned to this chasm of thieves. In obscure language, he prophesizes that Dante's party shall suffer greatly.
Canto XXV opens with the same sinner, Fucci, making "figs" with his hands and blaspheming God. A Centaur, Cacus, races up to the group and asks the location of the blasphemer. Virgil explains to Dante that Cacus does not reside with his fellows at the banks of Phlegethon because he stole Hercules' cattle. Hercules avenged the theft by clubbing Cacus to death, and he continued clubbing long after Cacus was dead. Suddenly, hoards of serpents climb on to Fucci and a dragon perches on his shoulders.
The Centaur leaves and three sinners appear, apparently concerned, asking if a sinner named Cianfa has fallen back. At that moment a six-legged lizard fastens itself to one of the three sinners, Agnello, and weaves itself through the sinner's body, melding it with the sinner, like hot wax. The two beasts become one and the other two sinners mock Agnello.
A small black monster runs up to one of the remaining two sinners and bites him near his bellybutton. A mutual transformation begins. The monster takes on the human form of the sinner, and the sinner takes on the monster's form.
