Commentary Purg XXXII 142-147

The language and the imagery are clearly indebted to the Apocalypse (13:1) for the beast with seven heads and ten horns.  Exactly what this symbolic transformation of the Church signifies is much discussed, with little resolution.  In general, all can agree, we here see the corruption wrought by the clergy upon their own institution.  In other words, in Dante's view, the Church had weathered all attacks upon it from within and without until the time of Charlemagne.  In the next five centuries she would do such harm to herself as to make those earlier wounds mortal.  This period is marked by corruption from the papacy down to the most modestly avaricious friar; Christianity has no enemies as implacable as its own ecclesiastical institutions or its own clergy.