There was only one requirement Ning had already decided on for the System he was going to make.
It could not attach itself to a Soul.
That single restriction eliminated most of the normal methods used to create Systems, but Ning had no intention of changing his mind about it.
Most Systems worked by attaching themselves to Souls while those Souls were on their way toward the Realm of Souls. At some point during that journey, the System would bind itself to the Soul and remain there until the Soul returned to a Realm of Matter.
It was also where several of their problems began.
One of the stranger side effects of binding Systems to a Soul during that process was that the cleansing of memories did not always happen properly. A Soul was normally supposed to lose the memories of its previous life before being reborn, but the presence of a System could interfere with that process.
The result was someone being born with memories they should not have possessed.
