Every Canto of this great work is complex and contains dozens of metaphorical scenes and actions. The heart of Canto XII seems to be the rugged, unstable landscape (emblematic of the difficulties of real life and the dangers awaiting the unsuspecting – cave-ins, precipices, collapsing relationship “bridges” and the like --) and the angry minotaur-bull-centaur who, once wounded, goes on a rampage of self-destructive behavior (a metaphor for man’s abandonment of Reason and moderation when in the throes of jealousy, revenge, greed, power, and similar emotional animal-like states, when the soul’s reason is overcome by animal instincts.) That is why tyrants are ensconced there. These two passages exemplify the metaphorical content:
As is that bull who breaks loose at the moment
In which he has received the mortal blow,
Who cannot walk, but staggers here and there,
The Minotaur beheld I do the like;
And he, the wary, cried: "Run to the passage;
While he wroth, 'tis well thou shouldst descend."
“A little farther on the Centaur stopped
Above a folk, who far down as the throat
Seemed from that boiling stream to issue forth.
A shade he showed us on one side alone,
Saying: "He cleft asunder in God's bosom
The heart that still upon the Thames is honoured."
Of course there is much more here, but the quintessential allegory is of instability of landscape and return to animal-like behavior when the base emotions overcome spiritual impulses.