Arioch! Arioch! Blood and souls for my lord Arioch!—Elric of Melniboné
Arioch is the most powerful Duke of Hell and one of the Chaos Lords, the god-like servants of Chaos in Michael Moorcock's multiverse, where he appears by name in both the Elric and Corum sagas. He holds several titles, including Knight of the Swords, Lord of the Higher Hell, and Lord of the Seven Darks. He is also the guardian and master of the Black Swords, Stormbringer and Mournblade. Arioch is sophiscated and highly intelligent, though often comes across as insane. His preferred form when meeting with mortals is of a beautiful youth with blonde hair, though he has manifested in other forms, including a large, black fly, a vaguely humanoid being of mist and flame, and a black alien shape that is too horrible for mortals to look upon.
In the universe of Elric, he is the patron god of Melniboné and personal lord over Elric himself, who's ancestor originally summoned him in ages past, Elric himself potentially being a reincarnation of this same ancestor. Meanwhile, in Corum, he is one of the Sword Rulers, the three gods of the Mabden race, alongside Xiombarg and Mabelode. In this manifestation, he was killed by Corum Jhaelen Irsei, though it should be noted that death for a Lord of Chaos only means that they are banished and unable to return to the universe in which they were "killed."