Anyone who studies the so-called "shadow magic" of the underworld's night blades is familiar with the siphoning spells, which drain life force and health from the injured to the injurer. The question before the scholar-arcanist is to explain how and why this works. After prolonged study, primarily through low-grade siphoning of my menials and their families while they slept, I have arrived at a hypothesis.
It appears to me that the magical siphoning of health is related to the instant translocation spells insofar as it creates a transliminal flow of essence from the target to the caster. Through the hyperagonal magicka sense, the night blade perceives the target's transpontine deformation and "pierces" it, and in the resulting disruption absorbs the essence that is lost by the target. Thus, instead of "stepping through shadows" as in translocation, the mage is "shadow draining" from one location to another.
Or so my experiments indicate.