Clutch & Opeth are not really festival type bands any way. The only one they both ever did was SOTU in '05. I think Opeth has too long of songs for this type of festival & Clutch have always been one of those bands who do their own tours. I don't see a ton of people in the Mayhem crowd that would get Clutch. Would have made it sweet but still no big deal.
10/7 - Run The Jewels