Board Thread:Spoilers!/@comment-1916997-20171216041419/@comment-34998786-20180315190027

The killer is not necessarily a killer. But it's certainly a wizard (or witch). A toft of hair is always taken from the victim. Hair is used in several magic practises, sympathetic magic or contact magic. It means that all these "ingredients" (but you need the total amount, otherwise eight, so also Ivy's is required, because she was a "member" of the coven, in the literal meaning) can "neutralize" the coven itself and its magic. It is also used in woodoo to have a precise effect in dinstance on the original owner of the hair used in the ritual.