Board Thread:Warhammer 40k General Discussion/@comment-28383085-20170330013226/@comment-29580146-20170405014315

A Chaos Grey Knight would be extremely lore-breaking. If you really, really, really want a Chaos Marine with Grey Knight armaments, you could have a Chaos Marine (a champion or warlord if you wanted) that wears the armour of a defeated Grey Knight, as a sort of insult to the Grey Knights.

That would be much more feasible than a corrupted grey knight