Noah had turned himself into a hybrid when he was only a human cultivator. His mind had reached the heroic ranks before the experiments back then, but he didn't have to face all the issues connected with individualities.
According to his own words, it was impossible to find a magical beast that suited the individualities' uniqueness. They didn't exist in nature, so no other creature could imitate them entirely, not even if planned.
However, Skully had lost her dantian long ago, and her personality had fallen apart in those millennia spent trapped under the rule of the Ape God.
Her entire existence had become an empty vessel filled with pieces of information regarding the Kesier species, and she had acquired some of their peculiarities too. She was the only cultivator who could claim to be entirely in tune with those beasts.