Shaula's Hair is the hair of the witch Shaula Gorgon.
It seems to be where a great vast of her Shaula's Magic lies an is often employed in combat, able to stretch distances. She is able to inject her venom  and utilize some of her magical spells. It is also very durable, able to block the demon weapon forms of Tsugumi Harudori's and even Clay Sizemore. It can only be penetrated when a weapon/meister pair has performed a Soul Resonance technique.