Wardruna

Wardruna is a Norwegian music group dedicated to creating musical renditions of Norse cultural and esoteric traditions. It was formed in 2003 by Einar Selvik along with Gaahl and Lindy Fay Hella. The band have since released three full-length albums, each based on a set of runes. Their third album, Runaljod - Ragnarok, was released on October 21, 2016. Wardruna make significant use of Nordic historical and traditional instruments including various percussion, flutes, kraviklyra, tagelharpe, mouth harp, goat horn and lur. Non-traditional instruments and other sources of sound like trees, rocks, water and torches are also used.
In 2014, Selvik announced on the group's official Facebook page that they would take part in composing the score for season 2 of Vikings along with Trevor Morris. He later appeared as an actor on the show. In 2014, Gaahl left Wardruna on amicable terms.
TeamRock.com described Wardruna's music as "a conjunction of the earthy, the organic and the ethereal" with "runic-based rites inhabit[ing] a frequency that once heard have always seemed just adjacent to everyday consciousness". Thanks in part to the success of Vikings, the band's 2016 album, Runaljod Ragnarok, debuted at No. 1 in Billboard's World Albums chart.
Selvik and Gaahl were both previously members of Gorgoroth, appearing together on the album Twilight of the Idols and the live DVD Black Mass Krakow 2004.
Selvik has also recorded with other projects including Det Hedenske Folk, Mortify, Bak de Syv Fjell, Jotunspor Sahg, Dead to this World and Skuggsjá.
Gaahl has also recorded with Trelldom, Gaahlskagg and God Seed.