Michael Moorcook is a British author of science fiction and fantasy literature, most prominent for his "weird fiction" focus; the high-magic Sword & Sorcery "Eternal Champion" universe, most iconic for the subsetting focused on Elric of Melnibone, is the most notorious of his many, many works.
So why is he here? Because he invented a lot of stuff seen throughout /tg/! Moorcock's Eternal Champion cosmology directly inspired both the Alignment system of Dungeons & Dragons and the Chaos Gods of Warhammer Fantasy and Warhammer 40,000, with the [eight-pointed star] of Chaos lifted directly from the Eternal Champion universe with almost no changes. In addition, Elric's cursed sword Stormbringer inspired the Dungeons & Dragons artifact called Blackrazor.