Transplantation

You take a severed body part from a creature and surgically, magically transplant it onto/into a different creature. The benefits of the body part and the surgical process needed in order to transplant it differ depending on what the body part is and what creature it came from. The area around where the body part was transplanted magically changes so that the internal mechanisms necessary for the body part to function are present (i.e. if you attach a third arm to someone under an existing one new bones, joints, muscles, nerves, and blood vessels grow so that the new arm functions correctly). Body parts that have begun to decay cannot be transplanted. 

The maximum number of additional body parts that can be transplanted onto a creature is equal to the number of hit dice they have. Body parts that replace lost or removed ones and additional phalanges (Fingers, toes, or their equivalents) do not count towards this total.