Inferno Canto XVII (the Seventh Circle, Third Ring: the Violent against Nature and Art)
Virgil, at his melodramatic best, heralds the monster’s coming: "Behold the beast… whose stench fills all the world!"
And here he is, "that filthy effigy of fraud," who has the face of a man, the body of a serpent, two paws, hair in his armpits, a really gaudy hide all braided and twisted into knots, and a pointy tail with a poisonous tip.
In a pretty funny simile (only made funny by its anachronism), Dante compares this monster to Germans and a beaver. Why? The beast is sitting on the riverbank, his tail dipped in the water, right on the boundary between land and water. Like Germany.
As for the beaver metaphor, apparently medieval biologists thought beavers caught fish by sticking their tails in the water and secreting some oily substance that fish liked.
Virgil makes the assumption that Dante wants to meet the ugly thing. So they walk towards it, being careful not to burn their feet.
When they reach it, Virgil’s reasoning takes another leap. He notices a few straggling sinners sitting on some rocks a few feet away. So he shoos Dante away towards them, encouraging him to "experience this ring in full." Meanwhile (get this), Virgil plans to negotiate with the monster to see if it won’t let them ride it into the next circle. (You do that, Virgil. We’ll scoot on ahead with Dante.)
Dante wanders off (read: runs away) to the sinners and notices them flicking their hands at the torturous flames.
Our hero doesn’t recognize any of them on sight, but he does recognize the little emblazoned pouches they wear around their necks. The symbols on them are crests of Florentine families famous for practicing usury. There’s a blue lion on a gold field, a white goose on a red field, and a pregnant blue sow on a white field.
The guy with the last purse is mean to Dante. He tells Dante to get lost because the spot where Dante is standing is meant for his usurer friend, Vitaliano. They’re all awaiting him and this other "sovereign cavalier" whose family emblem is three goats.
Intimidated by them, Dante won’t let on his annoyance and instead compares them to oxen.
Instead of staying to converse, Dante heads back to Virgil. Against all odds, Virgil has succeeded in gaining the monster’s trust.
Virgil orders Dante to climb up on the beast’s shoulders and sit in front of him, so that he can protect mortal Dante from the venomous tail.
Dante is quaking in his boots, but he’s not about to admit it to Virgil. Instead, he feels shame at his fear (especially when Virgil is showing none) and clambers on.
As always, though, Virgil is there for him and holds on to him as he calls the monster by name, Geryon, and instructs it to take off.
Geryon takes flight in a rather weird way, scrambling backward until there’s no more ground beneath him before spreading his wings.
Dante, wild with fear, still has the presence of mind to conjure up a simile, comparing Geryon’s movements to a boat backing away from its moorings.
Now Dante can’t stop with the similes; they keep coming as if from an unhinged poetic mind. Which is exactly what’s going on. Dante compares his fear to that of Phaethon (who lost control of his father’s sun chariot) and Icarus (whose makeshift wings melted because he flew too high).
He makes the mistake of looking down. But instead of passing out—as he might’ve done earlier —Dante simply clings tighter to Geryon’s back and absorbs all the hideous sights of sinners suffering.
Geryon flies downward in ever-decreasing circles, movement which Dante (still in a metaphoric frame of mind) compares to a trained falcon falling to the ground in exhaustion after failing to locate its prey.
Once they reach the bottom and our pilgrims scramble off, Geryon disappears.