Is this a metaphor a blackness darker than the night sky?

Yes, the phrase "a blackness darker than the night sky" is a metaphor. It evokes a sense of profound darkness or despair that surpasses even the deepest night. This comparison can be used to convey intense emotions, such as fear, hopelessness, or the weight of overwhelming experiences. The imagery invites readers to envision a darkness that feels all-encompassing and suffocating.