Short answers, pulled from the story.
Bastard!! was written and illustrated by Kazushi Hagiwara. It began serialization in Shueisha's Weekly Shonen Jump on the 14th of March, 1988, following a pilot one-shot titled Wizard!! Bakuen no Seifukusha published in 1987.
Bastard!! has over 30 million copies in circulation, making it one of Shueisha's best-selling manga series of all time.
Kazushi Hagiwara is an enthusiastic fan of heavy metal music and embedded band names throughout the series. Characters, locations, and spells carry the names of bands including Metallica, Megadeth, Anthrax, Guns N' Roses, Black Sabbath, Judas Priest, and others.
Yes. A 24-episode original net animation by Liden Films premiered on Netflix worldwide on the 30th of June, 2022. A second season of 15 episodes followed on the 31st of July, 2023.
A six-episode OVA produced by AIC was released between the 25th of August, 1992, and the 25th of June, 1993. It covers the story through the Four Lords of Havoc's battle against Abigail, corresponding to volumes 6-7 of the manga.
Hagiwara cited Go Nagai's Devilman as a primary influence. He also drew on the Dragon Quest video game series, the Fighting Fantasy gamebook series by Steve Jackson and Ian Livingstone, and the animation styles of artists including Tomonori Kogawa, whose work on Aura Battler Dunbine directly inspired the character Princess Sheila.