This was the first song that was written after Ozzy left the band. Not only did this feature new vocalist Ronnie James Dio but also Geoff Nicholls on bass as Geezer Butler left the band for a short period of time. It’s a demo version so it’s not the cleanest sounding but you definitely can tell where they were going to end up.
https://youtu.be/uAk4Z3sX0F4