I quite liked this creepy jaunt into facial hair mythology! I don't know that I have much to add to discussion directly, other than this reminds me of an idea I toyed with a while back about parasitic grass, which if you consider it, the hair could be parasitic, as it makes demons of those who take it as their own, the story might actually be even creepier if one discovered that they weren't actually demons/immortals, the hair was was a parasite that make them hallucinate, hmm.