A Slaaneshi Chaos Lord hailing from the Emperor's Children's now-destroyed homeworld, Chemos, Krax Concordius is a powerful corrupted Astartes who has led many campaigns of pleasure, pain and terror against the Imperium of Man. From the precipice of the Eye of Terror did he watch with glee as the Emperor's beloved Imperium degenerated into extreme ideological regression, and watching them delve right back into the superstition they once shunned.
Concordius is one of the oldest Chaos Marines in existence - he has roamed the galaxy since the Great Crusade, and turned to the service of Slaanesh during the Horus Heresy. He has been time and time again noted to much prefer the company of Chaos than he ever did "the Emperor's lapdogs", and shows little more than disdain for those who continue to worship him, hoping one day the Emperor might return. Krax Concordius however, prefers being in service to an actual god, and not a withered corpse on a golden chair.
After years and years, while Krax Concordius revels in the things he perverted or abused so long ago, Krax refuses to divulge any information he knew about the time. He especially does not want to detail his life on Chemos; Chemos was little more than a factory planet, and the future Astartes grew extremely weary and bored with having to do factory jobs over and over again thanks to the sacrifice of any leisure or pleasure that he once had. Knowing this, however, easily puts the pieces together.
It is plainly obvious that Krax turned to the service of Slaanesh after the misery and dreariness that was once his childhood before becoming an Adeptus Astartes. It is even possible he had done so in the closing years of the Great Crusade. Whatever the case, Krax clearly remembers many of the events that transpired in this time rather than having simply forgotten about it. Below details his "shenanigans" in the 41st Millennium.