A sort of temporary calligraphy mark based on the Mark of the Battling Gods. It helps train the yin and yang chakra to flow in new patterns, like a weight machine training muscles.
It was a training tool of an unconventional sort tailored to the bearers’ biology and ki generation system forcing the circular movement of energy as most humans have into the elliptical pattern for Double Circulation.
Like the original mark the 'array' itself, is superimposed on the midriff. It consisted of a tattoo of sorts, built around interlaced geometric shapes and a few other added pieces of script. As long as bearer wears it, it will light up when they exercise their auras and if the tattoo bleeds or the color changes, then so does the effect requiring it to be constantly checked and reinforced.
The Array can be made using either regular ink or a blood mixture in the ink. Human ki-saturated iron instead of just pure elemental iron as by mixing elements from bearers’ blood into the ink, it will become attuned to them and be unusable by anyone else.
Altered ki generation is still an experimental technique so there are still unforeseen consequences. The one time it was tested on a normal volunteer, a non-martial artist, it caused muscle damage. Luckily nothing serious, but it's still dangerous.