Well, there were lots of shadowy clubs in the Roman Empire dedicated to off-color deities.
I believe the archaic cults of Dionysus have already been mentioned, where women seized in divine frenzy supposedly uprooted trees with their bare hands and ate raw animal flesh. The associations with drinking wine, which was sometimes seen as the "blood" of the vine, and the interpretations of the perennial coming of the vine as resurrection and immortality, make it fertile ground for someone with imagination.
If we look to Germanic and Celtic societies, there are bands of sacred warriors that supposedly took on the spirits of animals (like bears and wolves), probably after ingesting certain drugs and working themselves into a frenzy through exotic religious rites.
In Egyptian mythology there is the tale of the warrior goddess Sekhmet. Sekhmet went out to destroy Ra the sun god's human enemies. She killed them and drank their pools of blood. But she didn't stop after the battle, and went out to destroy all of humanity. The world was saved only when the magician god Thoth tricked her into drinking a pool of red colored beer; thinking it was more blood she drank it, but got drunk and became pacified.