What makes Hammerheart by Bathory notable?

'Hammerheart' is recognized for pioneering the viking metal subgenre, influencing countless bands that followed. Its blend of heavy riffs and mythological lyrics garnered critical acclaim, solidifying Bathory's status in the metal scene and earning a legacy as one of the genre's most important works. By the time 'Hammerheart' was released in 1990, Bathory had transitioned from their raw black metal roots showcased in earlier albums to a more complex sound. This album marked a significant shift, being their first to explore viking metal themes, following the influential 'Blood Fire Death' which incorporated similar elements but was predominantly black metal.