Yin appears as a typical Penanggalan, a type of Malaysian vampire. She has a seemingly-normal human head with beautiful, flowing black hair, but her lower body is like something straight out of a nightmare: her spine dangles from the end of her torn neck, and all of the organs which would normally be found on the inside of a human body swing loose from her hanging vertebrae. Somehow, this whole form is held aloft in the manner of a snake poised to strike by the long strings of intestine which connect to this visceral mass.
In battle, Yin uses her splayed innards to snare those who come too close, usually as a result of the paralysing fear which her disgusting form inspires. Then, she will constrict the opponent with these venomous coils in the manner of some horrific serpent, by which point it is usually too late for the unfortunate victim, who will be drained of their life’s essence at her leisure.
It should be noted that Yin inspires a fear in others beyond even that which her repulsive form would suggest; she is a creature of pure evil, and those in her presence feel the dread aura which she exudes no matter how strong their will.
What Yin was before her coming to Malifaux is unknown; indeed she may always have been a Penangalan. However, her reasons for aiding mortals remain a complete mystery, even to those whom she grants her assistance to.