The Sin City fest also features Blue Öyster Cult, Down, Mayhem, Satyricon, Obituary, Warpaint, and more.
The legendary metal band is prepping its first new release since 1999.
The multi-day fest in Sin City will return in 2021, featuring most of the same band who were slated to play in 2020.
The festival was set to feature Slipknot, Judas Priest, Amon Amarth, and dozens more acts.
Blue Öyster Cult, Down, Mayhem, Black Rebel Motorcycle Club, Ty Segall, and Warpaint also confirmed for Sin City festival.
King Diamond revealed the sad news, mourning his “favorite bass player of all times.”
Judas Priest, Amon Amarth, and a reunited Mercyful Fate are among the top-billed acts for the annually stacked metal fest.
The bassist shared that he is battling cancer after it was announced that he would not be a part of Mercyful Fate’s upcoming reunion shows.
The legendary metal band has already booked a gig at 2020’s Copenhell fest in Denmark.