The Voice
While Bene Gesserit Mothers have all sorts of abilities, like reading people’s physiology to determine if they’re telling the truth, the more powerful ones have access to “the Voice,” a magical modulation of their vocal cords in a special way that forces the listener to do exactly what they say. It’s not really important how Reverend Mothers are able to do it, just that they can.
Of course, with great power comes great responsibility, and using the Voice too much would clearly bring all of their finely crafted long term plans crumbling down. Men aren’t supposed to know how to use the voice but Paul’s mother teaches him and he uses it to great and pivotal effect multiple times in the movies.
