People have been saying that Ghost ripped off Mercyful Fate pretty much ever since Ghost released Opus Eponymous in 2010. Though Mercyful Fate vocalist King Diamond doesn't really see it that way.
According to Diamond in an interview with Metal Hammer, Ghost's sound is more in line with Blue Öyster Cult than anything else. Diamond adds that he never felt Ghost was copying what he was doing either, and that their live shows are pretty different too.
"Some people have compared the two bands, but I never thought that. I very much saw them as a Blue Öyster Cult style band. I'm sure they have a little influence from us, and that's a huge honour to hear, but they have their own style. I never felt that they were copying us. We have all these guitar solos, and they barely use any guitar solos on those first couple of albums.
"They also have a show which is completely different to ours. You see someone saying 'Oh they got that from King Diamond and Mercyful Fate!' but I don't think that is true. It's not like we don't have any humour in our shows, but it's very grotesque and twisted. With them I see it as a lot more tongue-in-cheek. Ours is horror show, they have jokes going back and forth during the show."
"I'm not so much into the pop side of what they do, but they've certainly done some very heavy songs too. They do it very well, they're amazing songwriters."
Ghost mastermind Tobias Forge recently revealed he already has the name and concept for the next Ghost record. As for Mercyful Fate and King Diamond, they've both got records in various stages of completion.