"My weary frame
After short pause recomforted, again
I journey'd on over that lonely steep,
The hinder foot still firmer..."See in text(Canto 1)
One may interpret this line metaphorically as well as literally. The feet were thought to be the limbs of the soul: the right symbolizing the will and the left symbolizing the intellect. Dante requires both in his journey.
Plutus is a wolf in a metaphorical sense. The wolf, with its insatiable appetite, is a fitting figure for Plutus, with his insatiable hunger for material wealth.
"As falcon, that hath long been on the wing,
But lure nor bird hath seen..."See in text(Canto 17)
By comparing Geryon to a falcon that has not been able to find either food or a lure to justify his flight, Dante suggests that Geryon is displeased with the task carrying the two men. As soon as they land, Geryon disappears like an arrow from a bow, eager to be rid of them.
Daedalus and his son Icarus escaped from King Minos of Crete using feathers fastened onto a wooden frame with wax. As they soared above the Aegean Sea, Icarus flew higher than he was supposed to. Despite Daedalus' warnings, he flew high enough for the sun's heat to melt the wax. The frame lost its feathers, and Icarus fell into the sea—now called the Icarian Sea. Dante compares his own vertiginous dread to that of plummeting Icarus.
Phaeton is the son of the Greek god Apollo. When he was old enough, he begged Apollo to allow him to drive the sun-chariot across the sky. Despite Apollo's misgivings, he granted Phaeton the wish, but Phaeton soon allowed the horses to run wild. Because the earth was in danger of burning up as the sun came closer to the earth, Zeus hurled a thunderbolt at Phaeton, who fell from the chariot into the river Eridanus and died. Dante compares the dread he feels as he rides on Geryon's back to the dread Phaeton felt as he drove, and fell from, Apollo's chariot.
"E'en thus the cook bestirs him, with his grooms,
To thrust the flesh into the caldron down
With flesh-hooks, that it float not on the top..."See in text(Canto 21)
Dante compares the way the demons push the sinners back under the boiling tar to the way cooks push stewing meat back into the broth when it rises to the top of the cooking pot.
"In evolution moving, horse nor foot..."See in text(Canto 22)
The movement of infantry or cavalry on the field is known as an "evolution," part of an established pattern to get troops efficiently from one area to another and in the same order in which they started. In this context, Dante refers to his and Virgil's movements with the ten demons who are guiding them.
In this ditch are the hypocrites, who wear cloaks made of lead. These lead cloaks are painted with gold to metaphorically reflect how, while alive, these people disguised their malice with false good will.
The monks of the German city of Cologne—Köln in German—are known as "Clony." These monks inhabit the abbey founded by the Benedictines in 910 CE. As Dante mentions here, these monks wore their hoods so low as to veil their eyes.
"Minor Friars" are Franciscan monks, members of a monastic order founded in 1209. Following their spiritual leader, Francis of Assisi, the Franciscans strove toward humility and lived in purposeful poverty. They went begging in pairs, the older friar walking ahead of the younger. Virgil and Dante walk through the Fifth Pouch of the Eighth Circle in such a manner.
"As with circling round
Of turrets, Montereggion crowns his walls..."See in text(Canto 31)
Monteriggioni is a fortress near Siena whose walls are topped with a series of sixty-foot-tall sentry towers. In its design, it is a typical Tuscan fortified town of the 13th century. Dante uses Monteriggioni as a visual metaphor for the ring of turrets that gird the abyss at the heart of the Ninth Circle.
"Achilles and his father's javelin caus'd
Pain first, and then the boon of health restor'd..."See in text(Canto 31)
Achilles' spear, which was given to him by his father, Peleus, had the power to wound and to heal. Dante uses the spear as a metaphor for Virgil's sharp words, which first hurt Dante, then fortify him.