Welp, I have the Necron Codex, and it's official: Anything you thought were C'tan were probably not. The codex states that no one can really tell a C'tan apart from, say, a Daemon or other energy-based being(cause there are so many different kinds, right?) except the Necrons; not even the Eldar know how many are still out and about. So basically, something scary with super powers may or may not be a C'tan. It even states that Imperial records are so terrible that they're probably all wrong. There is no mention at all of the Ultramarines encountering the Nightbringer. No mention of the Deceiver linked with Pariahs(Which aren't mentioned at all in the codex.) Nothing at all of the Void Dragon on Mars(Which it probably isn't true anymore.)
Everything that we thought we knew was wrong, apparently, and we are advised to simply take all that stuff as lies and misinformation. "Just pretend it didn't happen." C'tan are footnotes in the history of the War in Heaven, and now used as semi-useful, sometimes-annoying MCs on the tabletop.
Yes, the new Cron stuff is cool. Yes, I like the dynasties and the characters and whatnot. But to have your race's gods be the sole reason that the Imperium exists as it does was pretty darn cool, and was the major reason why I loved Crons so much. Now? Who knows? There's nothing that explicitly denies all the old C'tan fluff, but there's now text that heavily implies all that stuff was untrue in the first place.
Ok, rant over, what do you guys think?