Steinar Sverd Johnsen is a Norwegian keyboardist and composer, born 1972. Sverd plays keyboards and synthesizers in Arcturus and was also the main composer for the band. He formed the band with Jan Axel Blomberg (also known as Hellhammer) of Mayhem in 1987, originally under the moniker Mortem (where he played guitar). The band split up in April 2007, but reformed in 2011.
In 1998, Sverd was recruited by the band, The Kovenant, known at the time as Covenant, along with Hellhammer. After the release of the album Nexus Polaris, Sverd and the band parted ways.
Sverd has also been a guest on a few releases by prominent Norwegian black metal bands, Ulver and Satyricon.