The dense dark gas capable of expressing different shapes of the "Breath" of the darkness element could be useful. Still, it wasn't a divine item, and Noah had already created his darkness.
His goal now was to build something stronger that didn't follow the laws of the world. The core item would also be his darkness, which was already outside Heaven and Earth's system.
So, the gas could only help him in his meditation.
As for the mirror, it was a divine item, but it didn't suit Noah's main inscription method.
It would still help him during his experiments, and using it with the Divine Deduction technique would reduce the time needed to complete his tests. Yet, it wasn't something crucial to his cultivation journey.
Also, the time spent in the experiments wasn't exactly wasted. Noah's expertise would increase as it did his understanding of a specific topic.
