“Yet in the abyss,
  That Lucifer with Judas low ingulfs,
  Lightly he placed us; nor, there leaning, stay’d;
  But rose, as in a barque the stately mast.”

Canto XXXII. Confessing that it is no easy task to describe the bottom of the universe which he has now reached, Dante relates how perpendicular rocks reached up on all sides as far as he could see.  He is gazing upward in silent wonder, when Virgil suddenly cautions him to beware lest he tread upon some unfortunate.  Gazing down at his feet, Dante then becomes aware that he is standing on a frozen lake, wherein stick fast innumerable sinners, whose heads alone emerge, eased in ice owing to the tears constantly flowing down their cheeks.

Seeing two so close together that their very hair seems to mingle, Dante, on inquiring, learns they are two brothers who slew each other in an inheritance quarrel, for this is Caina, the region where the worst murderers are punished, and, like every other part of the Inferno, it is crowded with figures.

                     “A thousand visages
  Then mark’d, I, which the keen and eager cold
  Had shaped into a doggish grin; whence creeps
  A shivering horror o’er me, at the thought
  Of those frore shallows.”

It happens that, while following his guide over the ice, Dante’s foot strikes a projecting head.  Permission being granted him to question its owner, Dante, because he at first refuses to speak, threatens to pull every hair out of his head, and actually gives him a few hard tugs.  Then the man admits he is a traitor and that there are many others of his ilk in Antenora, the second division of the lowest circle.

Canto XXXIII. Beholding another culprit greedily gnawing the head of a companion, Dante learns that while on earth this culprit was Count Ugolino de’Gherardeschi, whom his political opponents, headed by the Archbishop Ruggiero, seized by treachery and locked up in the Famine-tower at Pisa, with two sons and two grandsons.  Ugolino feelingly describes his horror when one morning he heard them nail up the door of the prison, and realized he and his were doomed to starve!  Not a word did the prisoners exchange regarding their fate, although all were aware of the suffering awaiting them.  At the end of twenty-four hours, beholding traces of hunger in the beloved faces of his children, Ugolino gnawed his fists in pain.  One of his grandsons, interpreting this as a sign of unbearable hunger, then suggested that he eat one of them, whereupon he realized how needful it was to exercise self-control if he did not wish to increase the sufferings of the rest.  Ugolino then describes how they daily grew weaker, until his grandsons died at the end of the fourth day, vainly begging him to help them.  Then his sons passed away, and, groping blindly among the dead, he lingered on, until, famine becoming more potent than anything else, he yielded to its demands.  Having finished this grewsome tale, Ugolino continued his feast upon the head of his foe!