As the name suggests, the function of the stone is to project an X-Ray vision of objects. Most commonly used for seeing what is behind doors and walls.
It is described as a tiny red rock that Nine takes from his chest and gives to Sam in the Mogadorian Mountain Base so that he can check the cells for his father, Malcolm. At the Dulce Base, Nine uses the stone to check behind a large door, expecting there to be an army of Mogadorians lurking on the other side.
- Continuity Error: Number Nine gives Sam the stone to use in the mogadorian mountain base but he is separated from Nine and Four before he could give it back. However, Nine later retrieves the stone from his chest.