In Chapter 8, Poole arrives at Utterson’s door in a state of high anxiety and terror, believing that Hyde has harmed Jekyll. As Utterson and Poole hurry back to Jekyll’s house, the moon is described as hanging sideways in the sky:
It was a wild, cold, seasonable night of March, with a pale moon, lying on her back as though the wind had tilted her [...].
This simile lends an atmosphere of chaos, changeability, and reversal to the night of Jekyll’s death. Even those elements that seem most fixed, like the moon in the sky, move as though affected by an unnatural force (here, an impossibly strong wind). The agency given to the moon, as she “l[ies] on her back,” is also off-putting. The moon follows the rules of nature. But on this particular night, “she”—the personified moon—has suddenly been given a new and threatening autonomy, threatening because it suggests that the typical laws of the natural world are open suddenly and without warning to change or manipulation. As it helps build an environment of urban chaos and dread, this simile feeds into the Gothic atmosphere that reigns throughout the novella.
This simile also reflects certain elements of Hyde’s arc over the course of the novella. Hyde, like the moon, was previously tethered by the laws of nature, and thus relegated to a secondary position within Jekyll’s ego. Under the influence of the supernatural experiments undertaken by Jekyll, though, Hyde gradually frees himself from his previous confinement. On the night this simile describes, that unshackling of Hyde from Jekyll’s consciousness is finally complete, as Jekyll transforms for the last time.
In the ninth chapter, Lanyon recalls going into shock after seeing Jekyll transform into Hyde:
My life is shaken to its roots; sleep has left me; the deadliest terror sits by me at all hours of the day and night [...].
Through the use of personification, Lanyon implies that the shock of seeing this transformation has rendered a permanent change in him. The great agency attributed to these abstract concepts of sleep and terror can be seen as another way of expressing the intractability of this change.
Lanyon says sleep has “left” him against his will. Similarly, terror is given the characteristics of a human companion who “sits” by him at all times. This description not only serves to give readers a taste of Lanyon’s psychic and emotional state after seeing the dark side of his long-time friend, it also feeds into the Gothic tradition of heightened, melodramatic depictions of emotion. It is not enough that the scene affects Lanyon deeply—it also must shake his life “to its roots.”
When Hyde appears throughout the narrative, Stevenson usually doesn’t linger too long on physical descriptions, instead focusing on the impression he makes on those around him. This scene is no exception: as much space is granted to Lanyon’s reaction as to Jekyll's actual transformation. The personification of sleep and terror here serves to deepen readers' sense of Hyde’s spiritual “deformity.” Hyde always inspires fear and hatred; the revelation that such evil could exist in a beloved friend is enough to turn someone's life upside down and cause reasonable men like Lanyon to lose their autonomy over their body and emotions.
Jekyll’s confession, which appears at the end of the novella, is marked by a refusal to take responsibility for actions taken by Hyde (though he admits that Hyde is an extension of his personality). His self-delusion is especially apparent when he personifies his "virtue," claiming that it was asleep when he discovered the potion that can divide the good and evil sides of of his personality:
At that time, my virtue slumbered; my evil, kept awake by ambition, was alert and swift to seize the occasion; and the thing that was projected was Edward Hyde.
He reflects that in his decision to move forward in experiments with Hyde, his “virtue slumbered.” Rather than speak in the first person and take ownership of the choice to move forward in his experiments, Jekyll describes his “virtue” as if it were its own autonomous entity. This rhetorical choice is a subtle means of abdicating responsibility.
Throughout his letter, Jekyll admits to privately indulging his own “undignified” urges. It seems that, through his own persistent interest, he has nurtured his darker side for many years. In this paragraph, he deflects responsibility for this, too. He personifies his “ambition” (presumably scientific or academic) as the force that has kept his “evil” side awake and ready to spring free after taking the potion. In this way, he uses personification to downplay and dismiss his poor decision-making.