@HC94 He's basically a Persian space wizard. But has a suprisingly sypathetic backstory. Essentially his Chapter leader made a well meaning but catastrophic mistake. Their emperor was enraged and consigned their order and planet to extermination and most of their former allies take part in doing so. His defeated and despairing leader and good friend makes a faustian pact with demons and basically becomes a demon lord who has lost all of his humanity. In order to save what's left of their legion they use dark magic and while they physically save them, most of them have been turned into mindless golems who are confined to their armor. Ahriman and his leader soon fall out and he now finds himself enemies of his former friend and leader. Ahriman now finds himself an outlaw from his former empire and hunted by grudge holding demons and former comrades. Despite this he's spent the ensuing centuries independently trying to find a way to cure his former comrades and hopefully defeat his former leader while taking part in heinous atrocities. Suprisingly sympathetic for a Chaos character