Any Fey hair, but specifically Archfey, were the main reason why we were hunted. Our hair had a lot of properties. Many that not even I have fully used. With Fey being the progenitors of most magical creatures, each Fey has the same unique qualities that the magical creatures that come from them have. Veela hair, for instance, has increased properties for pyromancy, spells to defy gravity, and vocal type spells. Due to their nature, it was temperamental in which the Veela who gives the hair must view the wielder as family.