Mayhem had released an EP, which didn't sound a whole lot like the output they would release later. The EP had a vocalist who went by the name Maniac, who when he left right after was replaced by the unfortunate Dead, who killed himself before they could record the debut album. They went and got Attila Csihar from a Hungarian black metal band to do vocals for the debut, and because they tended to have a revolving door of band members (no band member is on every album release), they hired 'close friend' Varg Vikernes, who had his own act as Burzum, to do bass playing under the name Count Grishnakh (which, along with 'Burzum', are names derived from JRR Tolkein). After the recording sessions and before release of the album Varg killed Euronymous, and as a result, dependent on what source you listen to, they buried Varg's bass in the mix or deleted it all together. When they returned as a functioning band they had a new guitarist and Maniac was back on vocals, as he was for further albums up until about 15 years ago when they brought back Attila, which is good as Attila is a h3ll of a lot better vocalist than Maniac. Anyway their last album from three or four years ago, "Esoteric Warfare", is actually very good, though it isn't really black metal anymore. The only members remaining from "Die Mysteriis Dom Sathanas" are Attila and the drummer 'H3llhammer'.
https://rateyourmusic.com/artist/mayhem - if interested I'd say find a download of "Die Mysteriis Dom Sathanas".
