Obviously it would be the end of the world if Opeth had to tour with slipknot, but I could see what would happen. You would get the Opeth fans and metal heads, and the kids that cut themselves all into a concert venue, add some alcohol and drugs, and then you hear all of a sudden during the Slipknot set "SLIPKNOT SUCKS" and it just leads to an onpour of it..... then all the metalheads triumphantly kill the kids that cut themselves and storm the stage where they steal all of Slipknots equipment, then realized it belongs to Slipknot and trashes it..... then they hunt down slipknot..... or at least it would be a great evening.... kill a few slipknot fans.... make a band feel bad about themselves..... get a little loaded....