World Eaters, from Slaves to Darkness. I love this illustration, it says so much about what the Chaos powers are. Look at the officer in the foreground. The only difference between him and a loyalist marine is the marking on his shoulder. He is no blood-mad fiend. He has just looked into the abyss that looks back, and been shown the truth about mankind’s insignificance.
That, my friends, is Chaos. Not spikes and and distended flesh. That’s just the surface that hides the psychological core.