Viking metal is a subgenre of heavy metal music with origins in black metal and Nordic folk music, characterized by a common lyrical and thematic focus on Norse mythology, Norse paganism, and the Viking Age. Its musical style is typically manifested as Nordic folk-influenced black metal. Some common traits include a slow-paced and heavy riffing style, anthemic choruses, use of both clean and harsh vocals, a frequent use of folk instrumentation, and, often, the use of keyboards for atmospheric effect. Viking metal developed in the 1980s through the mid-1990s as a rejection of Satanism and the occult, instead embracing the Vikings and paganism as the leaders of opposition to Christianity. Most Viking metal bands originate from the Nordic countries, and nearly all bands claim that their members descend, directly or indirectly, from Vikings. Bathory, from Sweden, is generally credited with pioneering the genre with its albums "Blood Fire Death" (1988) and "Hammerheart "(1990). Enslaved, Burzum, Emperor, Storm and Falkenbach helped further develop the genre in the early through mid-1990s. The death metal bands Unleashed and Amon Amarth, which emerged during the early 1990s, also adopted Viking themes, broadening the genre from its primarily black metal origin. Other key bands in the genre include Darkwoods My Betrothed, Einherjer, Ensiferum, Moonsorrow, Týr, Thyrfing, and Windir.