Complex sentence: Original Black Sabbath drummer Bill Ward returned to the band as a replacement for Vinny Appice, who had left with Dio to form the band Dio, and left the band right before the 1983 tour would ensue.
Split into simpler sentences: Original Black Sabbath drummer Bill Ward returned to the band as a replacement for Vinny Appice, who had left with Dio to form the band Dio. Ward left the band right before the 1983 tour would ensue.