The Thirteen Body Refinement's External Training consisted of five realms: Skin and Flesh, Tendon and Bone, Organs, Blood Marrow, and Opening Essence. As of today, Zhu Ju had already mastered the first four.
As for Opening Essence...
This Realm did not require tempering the Physical Body. Instead, it referred to one's entire Strength becoming one, integrated inside and out, and flowing without obstruction.
As long as the first four realms reached Perfection, one would naturally step into Opening Essence once their Strength could be commanded at will.
It required almost no active Cultivation.
Perhaps by simply relaxing, enjoying the scenery, appreciating tea and art, one could experience a moment of sudden enlightenment and take that final step, their Strength fusing and circulating perfectly.
