After freeing the Demigod of Rock you have to play as him to defeat the Scourge of Rock. The song you will play is by Megadeth and was written for Guitar Hero: Warriors of Rock so contains many guitar solos. The song is called “Sudden Death” and you have to get 30 stars in the song defeat the Scourge of Rock. 30 stars sounds a bit demanding up to this point considering you probably haven’t got more than 12 stars or so in a song, but try not to worry as this Demigod of Rock has all 8 powers combined. For most of the song you will constantly be in Star Power and on a 36x multiplier. If you are having difficulties on your chosen difficulty then drop down one and you probably have no problems gaining the 30 required stars.