Anima reveals itself in living things as an aura to those capable of detecting it. These auras, and the anima, glow with color. But there is anima without color that does not illuminate, but shades, drains, and darkens. This is Black Anima.
Black Anima is death energy. It is rarely used to bind anything wholesome. Corpses or minor constructs are often lightly bound in black anima, while the remains of potent individuals and artifices are heavily bound, so much that they drain the life energies from living things that draw to close, creating sensations of dread and freezing. Black anima often clings to such things, and even as the vessel it was once bound to rots away, it lingers on, ever so slowly loosing the memory of its shape. Some of the strongest stitchers of Black Anima are entities bound in it themselves.
Regular anima can also be used to bind corpses, but this is rarely done; anima stitched to a body is at risk of turning black. There are remnants of memory in the body, and binding such things can have erratic or even dangerous results akin to using a corpse brain as a control. Such animated bodies are sometimes used as guardians of wild places, where dark energy may be unwelcome, but erratic or dangerous guardians are of little concern or may even be desirable.