Prior to his service aboard the Enterprise, M'Benga interned on the planet Vulcan. During his time there, M'Benga witnessed Vulcans reading minds, planting delayed suggestions and even control weak minds from a short distance. He also heard some Vulcan legends relating to the Stone of Gol and its abilities to kill people using the power of their own thoughts. (TOS - Mirror Universe novel: The Sorrows of Empire)