Movie idea and background, Vampires

     The legend of vampires comes from aliens, and I say this for two reasons.

     One, as I fully know, human blood is an incredibly laxative.  If a human, or mutated human, drinks a human's worth, or even half, they will be stuck on the can for a day.

     Two, it is easy to imagine that an alien's eyes don't see the exact same spectrum as human eyes.  The reason why silver reflects is that we can't see the color of silver, it is outside our range.  If one had some other eyes, one could see the color of silver, and so that person couldn't see their reflection in a mirror. Not quit the same as not having a reflection, but pretty close.

     Of course, this would be a period piece, set in Eastern Europe, during the last, maximal, days of Ottoman control over that period.

     Such an alien could only plausibly be a tourist, or stopping by our planet for a meal.

     Being an alien could easily explain why direct sunlight was unpleasant, but not burning.  Either the eyes or the skin could be at fault.

     A good reason why a stake through the heart works could be that the alien has good self-healing, but such a large trauma to the heart, regardless of it being a wooden stake or not, is just too much.