A very rare and difficult form of alchemy is the manipulation of human souls. It involving the extraction of souls from human bodies and the alchemical binding of said souls to inanimate objects usually by way of a rune drawn in blood on the object itself. The iron in the blood bonds alchemically with the object and the blood itself
remains bound to the soul of the person from which it was taken. The Blood Runes themselves differ based on the theories and style of whatever alchemist performed the binding. In essence, these souls exist in the mortal plane without their bodies, are able to manipulate the objects to which they are bound and communicate verbally with beings around them but, of course, there are caveats. Despite the fact that these souls cannot feel pain or die by conventional means since the "bodies" they now inhabit are not mortal, the act of binding two such different things together is only temporary, as the soul and vessel will eventually reject each other and separate.