The Jettatura is the "Evil Eye," described as a sort of negative energy that has the power to curse crops or animals or other people by simply looking at them. The consequences of the Jettatura may result in crops failing or people falling ill.
The power cannot be forcibly attained; an individual will or not will have the power to induce the Evil Eye. As a result, most individuals discover they have the power by accident, usually when casting an envious or even admiring look at someone. A person with such a power must learn the discipline to control the ability or use it to curse others. Matt discovers during the events of City of Secrets that he can cast the Jettatura on others, but is alarmed at the consequences of the ability until Professor Constantin guides him as to how to resolve the situation.
The cure for the Evil Eye is relatively simple. A vessel of water is placed on the forehead of the victim. Oil is poured into the water; should the oil form the shape of an eye, it indicates that the victim has experienced the Evil Eye. The eye formed by the oil is to be "blinded" by grains of salt, which will remove the curse on the victim. When Matt accidentally casts the Jettatura on Jago Jones, Matt elects to lift the curse and succeeds with a makeshift version of the cure, using olive oil and sea salt with a mixing bowl filled with water.