The article notes that a Black Mass organized in USA (corrected, it was in Oklahoma apparently) had a stolen host that the attorney for the Black Mass promoter was legally compelled to return to the Church as being stolen property.
I somehow doubt that this heavy metal bar is interested in observing the proper protocols for a Black Mass and in having an actual stolen host, etc. More likely it will involve people dressed up as priests waving upside-down crucifixes and yelling Hail you-know-who, some scantily clad women and perhaps some people dressed as demons. It’s entertainment, not a serious religious gathering. Having said that, I still wouldn’t go to it. The devil is not something to play with in that manner.
Even if they are having a “sock drive for homeless shelters” as part of the Black Mass event.