Shikigami (式神) are a kind of spirit summoned to serve a practitioner of onmyodo, similar to a western witch's familiar. Shikigami cannot be seen by most people. Although invisible, shikigami could take a variety of human or animal forms, possess or bewitch people, or even cause harm or bodily death.
They were used by Momiji and Botan to send small paper-sized men towards Inuyasha and his crew. When they returned with a hair strand from Inuyasha, the priestesses were able to transforms them into larger versions of Inuyasha and replicate his powers. However, the transformed Shikigami were unable to replicate the powers of items the person was carrying.
- Shikigami on Wikipedia