What rhadomancers do is known as dowsing, which is a form of divination that uses a tool such as a pendulum or a forked stick to locate underground water, minerals, or other hidden objects. It is believed that the tool will move in response to unseen forces, and the direction of the movement can be interpreted to determine the location of the object. Dowsing has been practiced for centuries, and is still used today in some parts of the world.