The Sixteenth Æther.
The Siphonth is an ethereal parasite that feeds on its preys soul. This creature has approximately 5 seconds to decipher a lifeforms energy signature, if it does it can then begin to move in unison with the victims energy alignment and once it does it can latch onto the soul and begin feeding on its prey. Siphonth's can be exercised from its host with an energy realignment but most victims aren't aware of the problem until its too late.