Fell magical disease

Fell magical diseases are curses or spells put on someone to kill or harm them.

Background
Some theorise that Graham's heart disease was caused by fell magical disease. Though if that's true, no one knows who had cast it upon him. He did have many enemies both wizards and witches, including Mordack, Manannan and Hagatha, but also the The Enchanter and the late Dahlia. ...and Graham and his family had thwarted the Evil Family in the past first by saving Valanice from Hagatha but also his son turning Manannan into a cat.