Just yesterday I was reading about mythological creatures, and found one called -Empusa- and ended watching a report from spain about people who commit murder by cannibalism, accentuating that they drank their blood. Also, I have a Ripleys book, that said something about groups of people who get reunited several times a year to drink others blood. And well, in Asia xD they eat fetus. Although I dont know about tribes, I dont think you have to go that far. Nevertheless tribes are more interesting.
Well, there are a lot of sects. Ill research it, its a very interesting question. x)