Furthermore, the reason why Yuan Jie, Yuan Lun, Yuan Ling, and their Three Corpse Dao Bodies all practiced the Nine Yin-Yang Evolutions without additionally deducing a transformation technique suited to their own Great Dao was not because they could not deduce one.
On the contrary, if they intentionally deduced and created one, with the Nine Yin-Yang Evolutions as a reference, it would not be difficult for them to deduce it.
For example, Yuan Lun, who primarily cultivated Reincarnation, could initiate his transformation starting from the aspect of life-and-death reincarnation.
However, Yuan Yan stopped them, preventing them from independently deducing a technique suited to their individual Great Dao, having them all practice the Nine Yin-Yang Evolutions instead.
Doing so was in preparation for them eventually taking back and fusing their Three Corpse Dao Bodies, and even for him to take back and blend his Three-Selves Dao Bodies.
They all practiced the Nine Yin-Yang Evolutions, and their origins underwent transformation and sublimation through it. This caused their origins to derive the profound principles of the Yin-Yang Dao, producing connections as if they shared the same root and origin, making it much easier to blend and return to oneness. This should greatly reduce the difficulty of taking back and fusing the Three Corpse Dao Bodies and of evolving their own Primordial Dao Fruit to perfection.
Moreover, deducing and perfecting the Nine Yin-Yang Evolutions had consumed a great deal of his time and energy, and at times even required Yuan Jie, Yuan Lun, Yuan Ling, and him to link their minds and souls together to deduce and perfect it jointly.
If each of them had to deduce a technique suited to their own Great Dao, it would undoubtedly require a massive expenditure of time and energy.
It was not as if they had nothing