Simen Hestnæs (born 4 March 1974), better known by his stage name ICS 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 a vocalist and the bass guitarist to the heavy metal band Borknagar, and the former bass guitarist and clean vocalist for the symphonic black metal band Dimmu Borgir.