Dante explores the numerous circles of Hell in this story, in each of which a different sin is relegated. Throughout the story we have seen the punishments for a number of terrible sins, and in Canto 18, we come to the area where fraud is punished. The eighth circle of Hell, one of the worst, holds the eternal punishment for sinners guilty of fraud.
Within this circle is the priest, normally considered a holy man, and Dante is shocked to find a clergy member here in Hell. However, this gets to the heart of sin—that anyone can fall deeply into it. The priest is guilty of defrauding his congregation, and this is what Dante wants to comment on in the Catholic Church. He is angered at the amount of deception in the church and wants to condemn it in this work.