Among them is the witch Manto, to whom Mantua, his native city, owes its name, and Dante soon learns that all these culprits are the famous soothsayers, diviners, magicians, and witches of the world, who thus are punished for having presumed to predict the future.
_Canto XXI._ From the top of the next bridge they gaze into a dark pit, where public peculators are plunged into boiling pitch, as Dante discovers by the odor, which keenly reminds him of the shipyards at Venice.

Virgil there directs Dante's attention toward a demon, who hurls a sinner headlong into the boiling tar, and, without watching to see what becomes of him, departs in quest of some other victim.

The poet also perceives that, whenever a sinner's head emerges from the pitchy waves, demons thrust him down again by means of long forks.

To prevent his charge falling a prey to these active evil spirits, Virgil directs Dante to hide behind a pillar of the bridge and from thence watch all that is going on.
While Dante lurks there, a demon, descrying him, is about to attack him, but Virgil so vehemently proclaims they are here by Heaven's will that the evil spirit drops his fork and becomes powerless to harm them.

Perceiving the effect he has produced, Virgil then summons Dante from his hiding-place, and sternly orders the demon to guide them safely through the ranks of his grimacing fellows, all of whom make obscene gestures as they pass.
_Canto XXII._ Dante, having taken part in battles, is familiar with military manoeuvres, but he declares he never behold such ably marshalled troops as the demon hosts through which they pass.