What is the sin in canto 33 in Dante inferno?

In Canto 33 of Dante's Inferno, the sin depicted is treachery. This is symbolized by Satan, who is trapped in ice at the very center of Hell, as he betrayed God in Christian theology. The traitors in this canto are the three figures, Judas Iscariot, Cassius, and Brutus, who are being perpetually chewed by Satan.