The live album Dawn Of The Black Hearts was released in 1995 as a bootleg by the Colombian label Warmaster Records, which was owned by Mauricio Montoya, known as "Bull Metal", and who was a friend of Euronymous. Its cover has a photograph of Dead's suicide, taken by Euronymous himself. Dead's family and Necrobutcher did not agree with this cover and still reject it today.

Vocalist Attila Csihar has worked in film production, most notably serving as first assistant of production designer Norris Spencer in Tony Scott's film Spy Game.

The Mayhem logo was designed by Dutch goregrind legend Steven Smegma (Rompeprop, Bowelcrust, Smegma) who, when asked, drew it on an envelope. He still has the letter that Euronymous wrote to him when he asked for the logo.

Mayhem's vocalist, Per Yngve Ohlin aka Dead, used to cut himself while performing on stage. He would also attempt to stab people in the audience. During a gig in Sarpsorg, Dead was rushed to the hospital due to severe blood loss caused by the cut wounds he inflicted upon himself.
Rumors also say that he kept a dead raven in a bag, and would often smell it, just to feel the stench of death in his nostrils.
Before gigs he would wear clothes which he had buried in the ground several weeks earlier. It helped him create a corpselike image.

On August 10th, 1993, Varg Vikernes murdered Euronymous in his apartment. Their relationship before that was tense - one of the reasons being financial commitments Euronymous never fulfilled. Varg claims that Euronymous planned to murder him, and Varg went to his place only to confront him about it. Their talk quickly escalated into violence. Varg still claims that he acted in self-defence - however, there's evidence that the murder was planned beforehand, with elaborate alibi arranged. Varg was sentenced to 21 years in prison (the maximum possible sentence in Norway), for the murder and church burnings.

After the trial, the mother of Euronymous told Hellhammer to delete the bass lines that had been recorded by Varg. He said to her that he would personally play the bass, but the truth is that he had no idea of playing this instrument, so the album remained the same, featuring Varg Vikernes on it.

Dead committed suicide in 1991 by shooting himself in the mouth with Euronymous' shotgun after cutting his wrists with a machete. His body (wearing an ''I Love Transylvania'' shirt and leaving a suicide note saying ''Excuse all the Blood'') was discovered by Euronymous in his room. Before calling the police, he went to buy a disposable camera and took some pictures - one of them is now the cover of the infamous "Dawn Of Black Hearts" bootleg. It was also said that Euronymous had cooked and eaten pieces of Dead's brain and fragments of Dead's skull had been made into necklaces that both Euronymous and Hellhammer wore as a tribute to Dead.

Euronymous is Greek for "The Prince Of Death". He owned a small underground Metal store named "Helvete", Norwegian for 'Hell'. The store became a major spot for many Black Metal bands and members of the scene to gather. He also owned an underground label "Deathlike Silence", which name was inspired in a Sodom song. He released albums from such cult bands as Merciless, Burzum, Enslaved, Sigh and Abruptum.

Their band name is taken from the Venom song "Mayhem with Mercy." Many of the band member's names (Euronymous, Hellhammer, etc) were taken from songs by Hellhammer.