Cromm Cruaich
Cromm Cruaich stands slightly shorter than most Astartes, which obfuscates his frailer physique.  Hes had his skin stained a pale blue, similar to the primary blue of the Thousand Sons.  Several electoos were once installed on his back, but their mechanisms have failed, leaving only pale black quadrangles where once dynamic images had appeared.  Also apparent is that Cromm Cruaich is a eunuch, a gift from those who made him Astartes.  Lust is a distraction from ones studies, after all.

Cromm also bears a blasphemous symbol in a glowing gold: a Tzeentchy Chaos Symbol is upon his face,  The eye on the cross uses his actual eye and eyelid, with the cross extending down nearly to his jaw under the left eye.