Technically it's the MHI board
Okay, bear in mind the following things:
Any sufficiently advanced technology is indistinguishable from magic.
Quantum Physics allows for multiple universes.
Magic may exist in another universe, but not in ours, and it is possible it could leak over.
Here we go (in order of least likely to most likely):
Theory #1: Magic leaking over from an alternate universe where magic does exist. Or assuming magic does exist in our universe but has 'high-tides' and 'low-tides' and is not presently at high tide but that could change.
Theory #2: Bio-Medical Nanotechnology to regenerate dead tissue that causes a corpse to animate and is spread through bodily fluid contact.
Theory #3: Aliens using Nanotechnology to reanimate corpses to clean us from the planet so they can settle it.