What is "quorthon"

Tomas Börje Forsberg, known by the stage name Quorthon (17 February 1966 – c. 7 June 2004), was a Swedish musician. He was the founder and songwriter of the band Bathory, which pioneered the black metal genre and is credited with creating the Viking metal style. A multi-instrumentalist, Quorthon wrote the music and lyrics on all of Bathory's albums and performed vocals and guitars.