Ring of negation

A Ring of Negation was a cursed ring useful for controlling captive mages. The purpose of the ring was to prevent the wearer from casting spells. Whenever the mage wearing the ring attempted to use magic, searing pain shot up is arm. In theory, the ring could be removed by cutting off the finger. However, since so many spells depended on complicated hand gestures, removing the ring by amputating a finger wasn't a practical option.