Fabulous smiles amazing marines?
Just buy him than load up on all basic marines with the mark of khorne, a lascannon, and a melta. Keep firing the lascannons as he advances and when he's nearly within range, advance with fabius bile to fire his "wounds on a 4+" three shot pistol. Than just charge with the massive amount of marines, even after the charge they'll still be s5. And if you can afford as many as you possibly can, the nightbringer probably won't be able to kill them fast enough in CC before they drop it.