Final answer:
The use of figurative language in this excerpt conveys the speaker's shame and guilt over his wrongdoing.
Step-by-step explanation:
The use of figurative language in the excerpt from The Portrait of Dorian Gray by Oscar Wilde develops and enhances the speaker's tone by illustrating his shame over his wrongdoing.
The metaphor comparing his sins to the worm that eats away at a corpse conveys the speaker's deep guilt and remorse.
It emphasizes the destructive nature of his sins and the lasting impact they will have on the painting.