Simen Hestnæs (born March 4, 1974, in Oslo, Norway), better known by his stage name I.C.S. Vortex or simply Vortex, is a Norwegian musician. He is the vocalist of the similarly named band ICS Vortex, the avant-garde metal band Arcturus, and the doom metal band Lamented Souls. He is also the vocalist and bass guitarist to the progressive black metal band Borknagar, and the former bass guitarist and backing vocalist for the Norwegian symphonic black metal band Dimmu Borgir.