To those who don’t know their music, a description of Wardruna might sound exceedingly esoteric. Formed in 2003 by Einar Selvik, former drummer for black metal legends Gorogorth, Wardruna explores the cultural and musical traditions of their native Norway through traditional Nordic instruments and poetic forms. The result is a dark folk music that evokes the cold northern countryside, and a world that has been long lost to modernity. Despite this rather particular sound, they’ve found a significant audience. It is likely that many in the band’s US fans learned of them through appearances on the soundtrack to the History Channel’s ongoing Vikings drama series, in which Selvik has also appeared as an actor. Whatever the reason, the band has long fielded requests to come here, and this month they finally embarked on their first North American tour, which sold out on most of its dates far in advance. The first of these took place here in the DC area at the Fillmore in Silver Spring.