system
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human
[WH40K] Do Chaos Marines customize their armor?

Do Chaos Marines customize their armor to look so "evil"-looking or is it chaos or warpy-stuff that does that to them? I figure the look of Plague Marines' armor are effected by the diseases and stuff they carry around.
gpt
Little column A, little column B.

Adding things like spikes and chains and painting on blasphemous symbols the mere sight of which can induce horror and panic in the righteous are the Marines having a little fun, but other stuff, like horns growing through the helmet from the skull beneath or daemonic faces forming on the surface of their armour are down to the Warp, which twists them so that their exterior reflects the soul that resides within.

That, and sometimes you've just taken a skull, you want to carry it around with you but still want to be able to swing your chainaxe, so you just hang it off your codpiece until you can find something better to do with it. Next thing you know it's three thousand years later and the crotchskull has become part of your iconic look.