Immortal was a prominent black metal band from Bergen, Norway. The group began in 1989 as "Amputation", a death metal band. Immortal's early full-length releases were of a tradional black metal style, but their acclaimed album "At the Heart of Winter" saw the band begin to experiment with a complex fusion of black metal and German thrash. The resultant sound was a style which characterized Immortal's later works. Immortal has been influential to many modern heavy metal artists; its founders, Abbath and Demonaz, have attained a legendary status in the Scandinavian heavy metal scene, which includes many of the world's best black metal bands. Out of these many bands Immortal has arguably maintained the most occult-misticism image and way of life traditionally credited to black metal. Their peculiar music style of black melodic metal has guaranteed them a spot on the list of the best bands in the history of the genre, and has most definetely triggered the rise of their albums sales, even though most of the albums are quite difficult to obtain.
"Amputation" recorded their first two demos in 1989 with Demonaz Doom Occulta and Jorn Tunsberg on guitars, Abbath Doom Occulta on bass and vocals, and Armagedda on drums. The group changed its name to "Immortal" around 1991. Their third demo, Unholy Forces of Evil, saw a stylistic change to black metal and earned them a record contract. Tunsberg played many of the guitar parts of Immortal's first album Diabolical Fullmoon Mysticism, but is not officially credited.
Gradually, Immortal gained immense popularity in the underground, releasing several highly-acclaimed records on the French label Osmose. Unlike many other black metal bands, Immortal's lyrical theme was not based around Satanism, but rather dealt with an imaginary kingdom called Blashyrkh where an eponymous Raven-God of frost rules. Arguably, their best effort from this early period is Pure Holocaust, which served as a genre-defining milestone.