Another Mastermind?
Mana circuits.
The complex construct that serves as a bridge between the physical and spiritual for mortal beings. It exists both as physical and ethereal, never fully the other. A means that allows certain beings to perceive the spiritual and an integral factor to the manipulation of the spiritual energy in the world.
The mana circuits were also a manifestation of a soul. For this reason, every single mana circuit was different in its own unique way. That was why there were people with different attributes and so many different branches of magic in the world.
The mana circuit was flexible to a certain extent. If this extent is crossed, it results in the mana circuit collapsing and the soul of the body either being destroyed or forcefully removed. This left a soulless body that could remain immobile or act on simple instinct, basically a mindless beast that would eventually die. The time of death ranges, depending on the body.