As a child Blomberg’s main interests were football (soccer) and wrestling. At first he had no interest in drums or drumming, but as music became more appealing to him he started to find the different instruments interesting, which eventually lead to an interest in drums. His grandparents purchased him his first three drumkits; the first one was a four-piece jazz kit. With these he began learning how to play drums by playing along with albums he listened to. He was into heavy metal bands such as Iron Maiden and Slayer, but also bands like Depeche Mode and Duran Duran. He then found out about Venom and Celtic Frost and eventually jazz, due to influences from a past drum teacher.
Before joining Mayhem, Jan Axel Blomberg played in various local bands, including the progressive metal band Tritonus, where he met Carl August Tidemann, the man who became the Arcturus and Winds guitarist. He did some live performances as well, and then was hired by Mayhem, who needed to replace Kjetil Manheim; Blomberg got the job and took the pseudonym Hellhammer.
The first recordings he did with Mayhem were two songs for a compilation album around 1989, with the songs Carnage and The Freezing Moon. The first proper recording he did with Mayhem was Live in Leipzig in 1990. After that album, Mayhem had some trouble with the line up due to the suicide of the singer Dead and Necrobutcher’s departure from the band. During this time he founded the band Arcturus together with Sverd in 1991, out of the remains of the band Mortem. They released the 7″ My Angel in 1991 and later the mini album Constellation. In 1995 he joined Immortal as a session drummer during their tour that year, he also agreed to play drums on their first official Video, Grim and Frostbitten Kingdoms. He also briefly played for Emperor during this period. The recording and release of the Arcturus debut album Aspera Hiems Symfonia also happened this year.
In 1997 Jan Axel began working with Covenant, now known as The Kovenant, for the recording of their second album, Nexus Polaris. That album was released in 1998 with a following European tour. During 1997 Arcturus also released another album, La Masquerade Infernale. The next year another album from The Kovenant was released, Animatronic.
During the year 2000 he recorded a mini album with his new band Winds, Of Entity And Mind, which was released in May 2001. Winds also recorded a full-length album during spring 2001, Reflections of the I.
Jan Axel is now a two-time Norwegian Grammy Awards winner, in 1998 for The Kovenant with Nexus Polaris and in 1999 for The Kovenant with Animatronic. They claimed the prize for best hard rock album both years. In addition to these mentioned involvements, Jan Axel has also done numerous appearances as a guest or session musician on other releases.
In 2005, he was interviewed for the black metal mini-documentary that was included with the 2-disc DVD edition of Metal: A Headbanger’s Journey, in addition to other Mayhem members Necrobutcher (Jørn Stubberud) and Blasphemer (Rune Erickson).
In 2009, Hellhammer appeared on Eyes of Noctum’s album Inceptum, where he played drums on six tracks. Eyes of Noctum are a black metal band from America featuring Weston Cage, son of Nicolas Cage as their lead singer.
Hellhammer played with keyboardist Andy Winter on one of his albums.
Also in 2010, Hellhammer played on Nidingr’s latest album after 5 years, Wolf-Father. In 2011 Arcturus got back together again, with a new album set to be released sometime in 2013.