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