Why is Bastard!! full of heavy metal names?
Kazushi Hagiwara is an enthusiastic heavy metal fan, and Bastard!! is built from his record shelf at the level of its nouns. The hero, Dark Schneider, is named for Udo Dirkschneider, the original vocalist of the German band Accept; fittingly, the word that breaks Schneider’s seal in the story is “Accept.” Kingdoms, cities, villains, and spells take their names the same way: Wikipedia’s documented list of sources runs from Metallica and Anthrax to Bon Jovi, Judas Priest, Whitesnake, Megadeth, Venom, Guns N’ Roses, Black Sabbath, Stryper, and Helloween.
The names survived translation by transforming twice. The English editions took the Japanese transliterations of the band names and re-Englished them approximately, so Anthrax became the god Anthrasax, Iron Maiden became Aian Meide, and Metallicana became Meta-Rikana in Viz’s spelling. The references are catalogued in full on the English editions page; this page is about why they are there: for Hagiwara, metal was not decoration on the fantasy. It was the fantasy’s native language.