Compare Nathaniel Hawthorne's introduction of Dr. Chillingworth to his introduction of Mistress Hibbins in The Scarlet Letter.

When the narrator introduces Chillingworth, he is wearing a "strange disarray" of European and native attire.  His brow is "furrowed" and he is a somewhat small man, but he possesses a "remarkable intelligence in his features."  When he recognizes Hester on the scaffold, "A writhing horror twisted itself across his features, like a snake gliding swiftly over them."  Such a metaphor certainly helps us to understand that there is some evil in this man, that...

When the narrator introduces Chillingworth, he is wearing a "strange disarray" of European and native attire.  His brow is "furrowed" and he is a somewhat small man, but he possesses a "remarkable intelligence in his features."  When he recognizes Hester on the scaffold, "A writhing horror twisted itself across his features, like a snake gliding swiftly over them."  Such a metaphor certainly helps us to understand that there is some evil in this man, that he is, at least, capable of doing evil.  In a book where the Christian religion is so important, we cannot help but link this snake to the serpent in the Garden of Eden: the serpent was the devil in disguise.  Therefore, it helps to tell us aught of Chillingworth's nature and capabilities.

Later, when Mistress Hibbins is introduced, she is referred to as the governor's "bitter-tempered sister" who would later be executed as a witch.  Notably, she tries to get Hester's attention, whispering, "Hist, hist!" from her window.  This sound is remarkably close to a hiss, the sound made by a snake, which is precisely the animal to which Chillingworth was compared.  Thus, we can understand that she has a nature to do evil as well.  She invites Hester to a witches' meeting in the woods, saying that she told the devil himself that Hester would come.  If she is thus in league with the "Black Man," then we know that she is engaging in sinful behavior, and this description of her helps to shed light on the path Chillingworth is taking.