Final answer:
The phrases in question exemplify the literary device of contrast, which is used in poetry to highlight differences between opposing elements, create vivid imagery, and emphasize themes.
Step-by-step explanation:
The phrases 'Gold vs. Sable', 'Day vs. Night', 'White vs. Black', 'Dark vs. Fair', and 'Lightning vs. Thunder' all exemplify the literary device of contrast, where opposing elements are juxtaposed to highlight their differences. This technique is often found in poetry to create a vivid imagery or to emphasize a particular theme or idea. Since a specific poem containing these exact phrases isn't mentioned, it's unclear in which poem they appear. However, understanding the use of contrast in poems is beneficial as it can bring about deeper insights by comparing and contrasting different treatments of similar subjects.
By posing such contrasts, poets invite readers to explore the complexities within their themes, often evoking a range of emotions and thoughts. This technique engages readers by setting up a tension between two opposing images or concepts, making the poem more dynamic and thought-provoking. Furthermore, when poems use contrast effectively, they can leave lasting impressions by creating stark mental pictures or emphasizing certain arguments or ideas presented in the verses.