Ghost has had a history of employing stars throughout its live shows. We know that Dave Grohl has drummed for the band live at some point, we know that Halestorm's Lzzy Hale has served as a nun-figure handing out communion, and now we've got… someone playing cowbell.
Whether or not it's someone famous will probably remain a mystery, but still! Live Ghost cowbell is what the world needs anyway. MetalSucks points out that King Diamond lives relatively close-ish to where the shows were taking place in Texas, so maybe it was him? Maybe?
[youtube]https://www.youtube.com/watch?v=wbnLSFcfqhA[/youtube]