Obviously the citizens of the Empire know about Chaos – enough for normal folk to avoid it at all costs. But how much common (or uncommon) knowledge is there about the things that as players we all know about – four chaos gods, demons, beastmen, etc. I've always played WFRP with the assumption that most people know almost nothing about Chaos, to the point that many people are in denial about many aspect of Chaos ("Mutant beastman in the hills? What nonsense!"). Although I'm not sure that this fits with GW's current vision of the Warhammer world.
Anyway, as an extension of this, I am wondering if there is material out there that mentions alternative (and more subtle) names for the Chaos gods? The reason I ask is because I think of WFRP as, in some ways, being like Call of Cthulhu. There are dark, terrible gods but no one knows about them, and when characters encounter them, or their cults, they are referred to by names which don't reveal their true identity eg. "the black man" for Nyarlathotep.
Cheers.
....so yeah, I'm gonna do that more often, than just say, "the Tzeentch cultists stand arround a sacrifical altar, chanting as their magus do an impressive moonwalking".