Through pills or unique techniques, cultivators could warp their appearances to make them look young. Sometimes, even high-rank master teacher would be unable to see through some of these disguises.
On the other hand, a human's soul was forged at birth, and it would mature with the passing of time. There was no cultivation technique or means that could conceal one's soul age.
Thus, using one's soul to assess one's age was viewed to be the fairest method, and no one voiced any complaints.
Soon, all fifty-six participants had passed the crystal ball test. Most of them were between twenty-eight and twenty-nine, and the oldest of them all was twenty-nine-year-old and eleven months. Naturally, the youngest of the lot was Zhang Xuan.
He was still two months away from reaching twenty, and everyone couldn't help but be shocked upon seeing such a young participant-after all, the others were around a decade older than him.
Some of you might be familiar with Qi Men Dun Jia, I mentioned it a few times in the series when the formation (Life Gate, Death Gate etc) referred to them. Basically, in ancient times, it is a concept used in the military to set up formations, and eventually, it evolved to become a divination technique to predict the future and actions one should take to avoid future calamities.
I've tried to translate Qi Men Dun Jia into Mystic Gate Hidden Jia, which sounds awkward but I think it gives a better view of what the art is about. Each word has a specific significance, and Jia refers to the first of the Ten Celestial Stems (which used to refer to the first day of a ten-day week system in the Shang Dynasty).
According to Baidu, this is a 'military' version of the concept of Mystic Gate Hidden Jia:
The Hidden Jia refers to the high commander, who overlooks everything behind the scene.
The Three Mystic refers to the Strategy Department, Governance Department, and Logistics Department.
The Six Formalities (Which is connected to the Hidden Jia) are responsible for protecting Jia or the high commander, and they refer to the generals (namely, six of them).
This is just a very brief idea of how the Mystic Gate Hidden Jia builds up a system as translated from Baidu, and I think a similar but more intricate concept should apply for divination.