Steinar Sverd Johnsen (born 1972) is a Norwegian keyboardist and composer. Sverd plays keyboards and synthesizers in Arcturus and was also the main composer for the band. He formed the band with Marius Vold (Mortem, Stigma Diabolicum of Thorns, and Jan Axel Blomberg (also known as Hellhammer) of Mayhem in 1987, originally under the moniker Mortem (where he played guitar).
