Spirit Container Harvest was a compound Skill derived from the methods used by various humans and Pranic Beasts to harvest Parute Fruits. Inala had the methods of the Mammoth Clan, Cooter Clan, Gudora, Fhoong Brimgan, Mudropper, Centingers, Millingers, and a bunch more.
He had obtained the data of plenty of races that owned territories with Parute Trees, using a method each to delicately farm Parute Fruits without damaging the Parute Tree in the slightest.
Combining that data, Inala modified it to similarly harvest the Spirit Container of a person. Of course, this ability could only harvest one Spirit Container. So, the target must be at the Body Stage.
It was why Inala fed the Free Human a bunch of Elixirs until his Spirit Containers reached a hundred and fused into a unified whole. At this point, the sole influence on this unified Spirit Container was the Mystic Mist Art.