It's possible you're thinking of a similar idiom like:
* "Dark as night": This means extremely dark, often used to describe a situation where visibility is impossible.
* "Silent as the grave": This describes a complete lack of sound, often used to emphasize a quiet, somber atmosphere.
While "dead as night" doesn't have a specific meaning, it might be used metaphorically to describe something incredibly still, lifeless, or quiet. However, it's not a standard idiom and would likely be misinterpreted.
If you can provide context about where you encountered this phrase, it might be easier to decipher its intended meaning.