Undirheimar is a mysterious outfit. Promo materials and some casual Googling do not identify the musician or musicians behind the moniker. But that context is ultimately not too important. What matters, of course, is the music.
What we have here is a set of dark, ritualistic drones with martial percussion and throat-singing. The percussion consists mainly of repetitive, pounding drums that border on the overwhelming. The drones are similarly aggressive while the voices are guttural and invoke a set of mantras. Less obtrusive pieces are meditations or ceremonies with steady beats and slower growling voices.
Ultimately, the sound and feel are that of an amalgam of Nordic and Far Eastern folk styles, but with a heavy dose of imagination. Thus, cuts from Heljarrúnar might serve well as part of movie or television soundtracks in which Viking hordes – cloaked in the evening mist and hyped up by shamanic rites – descend on hapless villagers.