Bergen, Norway), better known by his stage name Abbath Doom Occulta, is a Norwegian composer, vocalist, guitarist, and one of the founding members of the influential black metal band Immortal. Before he founded Immortal, Abbath played bass for the early Norwegian extreme metal band Old Funeral, with future Immortal member Demonaz and Varg Vikernes of Burzum fame (Though they were all not in the band at the same time). While working with Old Funeral, he also joined Demonaz's band Amputation who later became the infamous Immortal. He also play bass in Demonaz newly started project Perfect Visions.
Immortal's history begins in 1989 as death metal band Amputation. At various times throughout Immortal's existence, Abbath was lead vocalist, bassist, guitarist, keyboardist, drummer, and lyricist, mainly due to the inconsistent line-ups they were able to put together. During a long period of time, however, Abbath served the band as Vocalist, Bassist and (studio) Drummer while Demonaz played lead guitar. It wasn't until Horgh arrived that Immortal was able to secure a steady line-up; the problems however continued. After the release of Blizzard Beasts Demonaz was diagnosed with acute tendinitis, and was consequently forced to quit as guitarist, but remained as lyricist and band manager. They released At the Heart of Winter in 1999, this time with Abbath handling guitar and bass, with Horgh still on drums. This album marks a large shift in sound and style for the music of Immortal. In 2000 they released Damned in Black, with Iscariah on bass. Sons of Northern Darkness was released in 2002, with the same lineup.

Soon after the release of Sons of Northern Darkness, Immortal ceased to exist. The break-up was not caused by tensions or problems, but was rather a mutual one between all members, who claimed to do this for personal reasons.

In early June 2006, it was announced through a German Rock Hard magazine, that Abbath and Horgh would reunite as Immortal. They have begun practicing old material. In regard to when Immortal would start playing live again, Abbath is quoted saying:

"One year more or less doesn’t make a difference. We have all the time in the world."

Abbath used to use a GHL Jackson Randy Rhoads copy which he modded with new pickups, hardware, and a new paint job. Currently hes been using an ESP LTD DV8 Dave Mustaine Model which he modified to accept a Floyd Rose tremolo system. He might use Marshall Amplifiers. This is not confirmed.
In 2006, Abbath started a new band called simply, "I". Abbath is the frontman and guitarist of "I" and is joined by former Immortal drummer Armagedda on drums, Gorgoroth bassist TC King on bass, Enslaved guitarist Arve Isdal on guitars, and former Immortal guitarist Demonaz writing lyrics. The debut album called "Between Two Worlds" was released in 2006.