Eirik “Pytten” Hundvin's frostbitten and reverberating production has been a secret ingredient on albums by Norwegian black metal acts since the early '90s: Aeturnus, Burzum, Enslaved, Gorgoroth, Immortal, and many more. All along he's lent folk, ambient, medieval, or symphonic nuances to some of the planet's nastiest, most brutal music.