Formskul

"The surgeons placed within his opened cavity dozens of metallic spheres, like freezing marbles that stung his insides with icy intensity. Each of these tiny orbs sank deeper inside of Johannes, inching their own way to find a nice, warm crevice to tuck themselves into." "—The Sword and Its Servant " Formskul were metallic spheres the size of a marble used by practitioners of the Fleischkraft to imbed in their victims to assist in transmutations.

Formskul were actually living creatures.