Vampires - Guess that's good to know

This also explains why vampires don't show up in photographs in folklore, as silver-based chemicals (such as silver nitrate and silver halides) were key ingredients in early photographic mediums like plates and film.

Shove vampire into a tube. Affix a light source to one end, a mirror to the other. The side of the vampire with the light source absorbs the light directly, on the side with the mirror, the light still comes from the mirror because of the lack of reflection. More energy is produced than what is provided to the light source, violating the conservation of energy and becoming an infinite source of power. Vampires are the solution to the energy crisis.