At long last, Matilda’s hidden motives for helping Ambrosio this entire time are revealed: she was a demon sent by Lucifer to prove how easily the devil can lead any mortal astray, even a mortal as pious and devout as Ambrosio once appeared to be. This reinforces the book’s broader point about human nature’s tendency to undermine abstract moral frameworks. Lucifer’s next shocking admission that Elvira is Ambrosio’s mother and Antonia is Ambrosio’s sister, in addition to resolving the question of Ambrosio’s mysterious origins, adds an extra layer of depravity to Ambrosio’s sin of murder: not only has he murdered two innocent women, but he has also committed incest. Lucifer’s final admission—that Ambrosio’s life would have been spared had he just waited a moment longer before selling his soul to the devil—drives home the book’s broader point about the folly of pride. In his vain efforts to avoid the mutilation of his flesh, he has doomed himself to a far worse fate: eternal damnation.