Yesterday I started working on a custom Cypher model. But all I had were chaos parts, so I came up with a little story so it would make sense.
What if Cypher's sword, which he conviniently never unsheathed, was actually a daemonic artifact slowly turning him. He knew most of his potential allies (all of the armies that can choose him except chaos) would turn him in on the spot if he was seen walking around with a chaotic artifact like that. Thats why he put a wrap around it, or a sheath in some depictions of him. And never again would he show it to anyone. The sword gave him beyond natural powers, it could make him dissapear instantly, only to reapear on the other side of the galaxy. It gave him an incredibly long life span, but such great power comes with a price... The sword was slowly corroding his mind. It took the sword more than 10,000 years to finally turn him over to the chaos gods... But at last it was done, Cypher the fallen angel was now a Champion of Chaos.
Also if you want to see my cypher model, here is a link to my P&M post showing him and the inspiration I used for him off.
http://www.dakkadakka.com/dakkaforum/posts/list/620557.page