Short answers, pulled from the story.
Bathory released Blood Fire Death in 1988, marking a pivotal shift from Satanism to Norse mythology within heavy metal. This album featured The Wild Hunt of Odin on its cover and created an early blueprint for the genre by incorporating Viking themes into songs like A Fine Day to Die.
Norway's Enslaved emerged as another foundational force when they formed in 1991 and released their 1993 EP Hordanes Land which is often cited as the first true Viking metal release. Their music set out to create sound devoted to retelling Norway's legends and traditions without attacking Christianity through Satanism.
Vikernes burned the twelfth-century Fantoft Stave Church in Bergen on the 6th of June 1992 related to Number Beast due date being sixth day week sixth month sixth year. He contends the date picked because first recorded Viking raid upon Lindisfarne occurred according to him the 6th of June 793.
Viking metal artists rely extensively on keyboards played at a swift galloping pace to create atmospheric effects while adding local cultural flourishes such as traditional instruments and ethnic melodies. The genre incorporates both singing and typical black metal screams and growls into its vocal styles yet uses folk instruments less extensively than folk metal.
Some members believe impossible someone be Viking unless themselves northern European descent and practically all bands claim Viking ancestry directly or indirectly from Scandinavia. Bands formed United States Canada with members claiming Viking descent either directly from Scandinavia through England while others spread areas historically settled Vikings including England Russia Normandy.