ZYKLON-B was a 1994 side project from EMPEROR members guitarist Samoth (a.k.a. Tomas Thormodsæter Haugen) and Ihsahn (Vegard Sverre Tveitan) colluding with Frost (Kjetil Haraldstad) of SATYRICON and Draug Aldrahn (Björn Dencker Gjerde) of DØDHEIMSGARD and THORNS. Naturally the provocative band title, Zyklon-B being the poisonous chemical used as the killing agent in the holocaust of World War II, drew swift criticism, prompting a statement declaring non-political aims.

The endeavour issued an eleven minute mini-album, made available on both CD and 12" vinyl format, entitled 'Blood Must Be Shed' through Malicious Records. The album would see a re-issue, adding an extra re-mix track, a year later courtesy of Hammerheart Records. This extra song would also be featured on a split 7" single 'Total Warfare (Sea Serpent Remix)' shared with MAYHEM, again released by Hammerheart. 'Blood Must Be Shed' is regarded by many in the Black Metal field as a pioneering cult release.

The band reformulated for a second album, simply credited now to ZYKLON, having the EMPEROR members guitarist Samoth and drummer Trym colluding with Destructor of MYRKSKOG. Guesting on the 2000 'World Ov Worms' album is LIMBONIC ART's Daemon, ULVER's 'Trickster G' (actually frontman Garm) and the American fetish star Persephone.

British Black Metal band REIGN OF EREBUS covered 'Warfare' on their 2004 album 'Inversion Principle'. In late 2005 IHSAHN revealed he was working on a debut solo album. 'The Adversary' featured Asgeir Mickelson from BORKNAGAR on drums.