In fact, the main body of the Soul Splitting Secret Technique is essentially a variant of the accompanying Summoning Ceremony.
Only, this secret technique replaces the summoned creature's self-consciousness with the consciousness of the Summoner.
The Caster needs to separate a thread of their own soul as a seed, which merges with the summoned creature's soul that has had its consciousness erased, thereby gaining control of the summoned creature's body.
The reason the soul is not completely erased is that some powerful abilities are often related to the soul.
If the soul's form is too distinct from the body, then even after obtaining the summoned creature's body, these abilities cannot be accessed.
Leaving the ceremonial room and entering the Magic Test area of the laboratory, Anvis released the incarnate body of the Power Dragon. The original body, following the incarnate's sensations, entered the Summoning Space in reverse.