The manas is the core of Yogācāra practice and realization

In the cultivation and realization of Yogācāra, the manas is the core. Because the tathāgatagarbha does not need anyone's instruction to suddenly change, one can only apply one's mind to the manas; by changing the manas, one changes the person—from an ordinary being to a Buddha at the stage of fruition. Only by changing the manas can all dharmas be changed.  

All ignorance resides in the manas. When the ignorance of the manas is eliminated, one becomes a Buddha; changing the manas changes the seeds, and when the seeds are changed, one becomes a Buddha. The ignorance of the mind consciousness all comes from the manas; it is only by relying on the manas that the mind consciousness and its ignorance exist. The mind consciousness and its ignorance are easy to eliminate—not difficult at all. The difficulty lies in the manas. Therefore, the mental factors of the manas cannot be so much fewer than those of the mind consciousness; they should be roughly the same as the mental factors of the mind consciousness. If both one's meditative concentration and one's power of observation are severely insufficient, one cannot realize the manas, let alone observe the operation of the manas's mental factors. The state of the manas's operation within any given dharma would then be unknown and unrealized, and so one would dare to recklessly deny the various mental activities of the manas, insisting that they are instead the mental activities of the mind consciousness.

If the manas does not realize the dharma, ignorance cannot be eliminated; even eliminating the ignorance of the mind consciousness is useless and cannot change anything. It now appears that no matter what one does with the mind consciousness, it is of no use; the cultivation and realization of all dharmas must reach the manas before the fundamental problem can be resolved. Once this line of thinking is clearly understood, there should be nothing more to say about the cultivation and realization of the Buddha's teachings.