"The Heavenly Source Mirror has levelled up quickly, and has become a Great Sage Tool after it has swallowed so many sage tools!" Ye Mo merrily stated. Great Sage Tool and sage tool were two entirely different concepts. In fact, there was a difference of cloud and mud between them.
Ye Mo had sustained injuries to his essence. However, the Heavenly Source Mirror had nothing to do with that. In fact, Ye Xiwen hadn't seen the injuries affecting the essence of the Heavenly Source Mirror.
Therefore, Ye Mo had swallowed the tool spirits of many sage tools in order to replenish his essence. It was similar to when Ye Shu had swallowed other book demons in order to strengthen his essence.