Which lead vocalist wrote songs for Black Sabbath?
The Mob Rules:  The song was written by Ronnie James Dio and Tony Iommi. Mob Rules (album):  It followed 1980's "Heaven and Hell", and it was the second and last Black Sabbath studio album to feature lead vocalist Ronnie James Dio prior to the 1992 album "Dehumanizer".
Ronnie James Dio