Answer:
The answer is Twilight
Step-by-step explanation:
Twilight is the metaphor for aging the Shakespeare uses.
A metaphor is understood as a figure of speech that describes an object or action in a way that isn’t literally true, but helps convey an idea or draw a comparison.
A metaphor states that one thing is another thing.
Metaphors are used in poetry, literature.
So, this literary device is implemented in order to encourage the reader to make a comparison between two seemingly unrelated things.